Title of Invention	"A PROCESS FOR THE PREPARATION OF A NOVEL HYDROPHOBIC MULTICOMPONET CATALYST, USEFUL FOR THE DIRECT OXIDATION OF HYDROGEN BY OXIDATION OF HYDROGEN BY OXYGEN TO HYDROGEN PEROXIDE
Abstract	A process for the preparation of a novel hydrophobic multicomponent catalyst, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide A process for preparation of a novel hydrophobic multicomponent catalyst has been developed , which can be used for the direct oxidation of hydrogen to hydrogen peroxide even at atmospheric pressure, showing high hydrogen conversion activity and high selectivity for the hydrogen peroxide formation.

Title of Invention

"A PROCESS FOR THE PREPARATION OF A NOVEL HYDROPHOBIC MULTICOMPONET CATALYST, USEFUL FOR THE DIRECT OXIDATION OF HYDROGEN BY OXIDATION OF HYDROGEN BY OXYGEN TO HYDROGEN PEROXIDE

Abstract

A process for the preparation of a novel hydrophobic multicomponent catalyst, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide A process for preparation of a novel hydrophobic multicomponent catalyst has been developed , which can be used for the direct oxidation of hydrogen to hydrogen peroxide even at atmospheric pressure, showing high hydrogen conversion activity and high selectivity for the hydrogen peroxide formation.

Full Text	This invention relates to a novel hydrophobic multicomponent catalyst, useful for the direct oxidation of hydrogen to hydrogen peroxide, and its method of preparation. This invention particularly relates to a novel hydrophobic multicomponent catalyst comprising a hydrophobic polymer membrane deposited on a Pd containing acidic catalyst, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide, and its method of preparation. The hydrophobic catalyst of this invention could be used in the chemical and petrochemicals industries for the production of hydrogen peroxide by direct oxidation of hydrogen by oxygen to hydrogen peroxide, which is an environmentally clean process. Since the disclosure in U.S. patent 1,108,752 by Henkel et al. that palladium is a catalyst promoting the formation of hydrogen peroxide and water from a mixture of hydrogen and oxygen, a number of palladium containing catalysts, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide, have been disclosed by many inventors. Hydrophilic Catalysts for Direct Oxidation of H 2 by O: to Hydrogen Peroxide A U.S. patent 4,832,938 by Gosser et al. disclosed a Pt-Pd bimetallic catalyst supported on a carbon, silica or alumina support for making hydrogen peroxide from direct combination of hydrogen and oxygen in an aqueous reaction medium. Later, a German patent Ger. Offen. DE 4,127,918 Al by Lueckoff et al. disclosed a supported palladium gold catalyst for the manufacture of hydrogen peroxide from hydrogen and oxygen in aqueous medium; the catalyst contains 5 - 95 wt % Au and is supported on carbon. A number of platinum Group metal containing catalysts: (1) Pt-Group metal on high surface area support, such as carbon, silica or alumina (Ref. U.S. patent 5,169,618); (2) Pt-Group catalyst on solid acid carrier (Ref. Eur. Pat. Appl. EP 504,741, Al); (3) Pt-Group element supported on Nb- or Ta oxide (Ref. PCT Int. Appl. WO 9,412,428 Al); (4) Sn- modified Pt-Group metals supported on catalysts carriers (Ref. Eur. Pat. Appl. EP 621,235 Al); (5) Pt-Group metal catalyst supported on hydrophilic support (Ref. U.S. patent 5,399,334); for the oxidation of hydrogen to hydrogen peroxide are known in the prior art. The above mentioned Pd- or Pt-Group metal containing catalysts are hydrophilic in nature, and hence the aqueous reaction medium used in the oxidation of hydrogen to hydrogen peroxide over these catalysts is in close contact with the catalyst surface. Because of the close contact between the catalyst and the reaction medium, the hydrogen peroxide, which is formed by the reaction between hydrogen and oxygen on the catalyst and then absorbed in'the reaction medium due to a high affinity between hydrogen peroxide and water, is readsorbed on the catalyst from the reaction medium and converted to water and oxygen, and thereby the selectivity for hydrogen peroxide is drastically reduced, when the above mentioned catalysts are used in the oxidation of hydrogen to hydrogen peroxide. Earlier, Fu et al. has also found that only the Pd catalysts supported on hydrophobic support are selective towards hydrogen peroxide formation in the oxidation of hydrogen [ Ref. L. Fu et al., Stud. Surf. Sci. Catal., 72(1992)33-41]. Hydrophobic Catalysts for Direct Oxidation of H: by O2 to Hydrogen Peroxide A few Pt-Group or Group VIII metal catalysts deposited on hydrophobic support, useful for the oxidation of hydrogen to hydrogen peroxide, are also known in the prior art. A Japanese patent Jpn. Kokai Tokkyo Koho JP 01133909 A2 by Kyora disclosed a Pt-Group metal catalyst carried on a hydrophobic support such as porous and hydrophobic Teflon support. Chuang in an European patent EP 3660419 Al disclosed a Group VIII metal catalyst deposited on a hydrophobic support for the manufacture of hydrogen peroxide by reacting hydrogen with oxygen in an aqueous medium. Later , Chuang has disclosed a Group VIII metal on a partially hydrophobic and partially hydrophilic support, such as Pd on fluorinated carbon, as a catalyst for the oxidation of hydrogen to hydrogen peroxide, in PCT Int. Appl. WO 9314025 Al. Although, the hydrophobic support used in these catalysts provides some hydrophobic character to the Pd - or Group VIII metal catalysts, there are following disadvantages and limitations of the use of hydrophobic support for depositing the metal catalysts : 1) It is difficult to deposit catalytically active components from aqueous solution on a hydrophobic support as there is no wetting of the surface of hydrophobic support by aqueous solution. 2) Hydrophobic support, such as teflon and other hydrophobic polymer support, is thermally unstable at the calcination temperatures normally employed for decomposing the precursor compounds of catalytically active components of the catalyst. 3) Because of the deposition of catalytically active components, which are hydrophilic in nature, on hydrophobic support, the hydrophobic character of the support is lost completely or at least partially. Apart from the above mentioned disadvantages and /or limitations, the prior art catalysts with or without hydrophobic support are employed in the oxidation of hydrogen by oxygen to hydrogen peroxide at a pressure which is much above the atmospheric pressure. At the higher pressure, the explosion hazardous for the reaction between hydrogen and oxygen are more. » Hence there is a need for developing a new catalyst which is active in the direct oxidation of hydrogen to hydrogen peroxide even at atmospheric pressure and also has a hydrophobic character so that selectivity for the formation of hydrogen peroxide by the reaction between hydrogen and oxygen in an aqueous medium is high. Accordingly, the main object of the present invention is to provide a novel hydrophobic catalyst , which is free from the above mentioned limitations, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide with high selectivity and a process for the preparation of the novel catalyst. Other object of this invention is to provide a novel hydrophobic catalyst comprising PdO in a highly acidic environment, created by a solid acid or a solid super acid, so that the catalyst shows both high activity and high selectivity in the direct oxidation of hydrogen to hydrogen peroxide. Yet another object of this invention is to provide a novel hydrophobic multicomponent catalyst, which can be used for the direct oxidation of hydrogen to hydrogen peroxide even at atmospheric pressure, showing high hydrogen conversion activity and high selectivity for the hydrogen peroxide formation. These and other objects are accomplished by providing a process for the preparation of a novel hydrophobic multicomponent catalyst, comprising a hydrophobic polymer membrane deposited on a highly acidic Pd containing catalyst. Accordingly, the present invention provides a process for the preparation of a novel hydrophobic multicomponent catalyst, comprising a hydrophobic polymer membrane, useful for the direct oxidation of Ha by 02 to hydrogen peroxide and is represented by the formula: R(a)/AxByPdOz(b)/X(c)/MOn(d)/N wherein: R is a hydrophobic polymer, which forms a hydrophobic polymer membrane permeable to hydrogen, oxygen and hydrogen peroxide vapors; A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or a mixture thereof; B is a noble metal element other than palladium selected from the group consisting of Ru, Pt, Rh, Ir, Os, or a mixture thereof; Pd is palladium element; 0 is oxygen element; X is a halogen element selected from F, Cl, Br, I or a mixture thereof; M is an element selected from S, P, Mo, W, Ce, Sn, Th or a mixture thereof; N is a catalytic porous solid as defined herein , optionally supported on a conventional catalyst carrier; x is a A/Pd mole ratio in the range of zero to 1; y is a B/Pd mole ratio in the range of zero to 0.5 ; z is a number of oxygen atoms needed to fulfill the valence requirement of AxByPd; n is a number of the oxygen atoms needed to fulfill the valence requirement of M; d is a weight percent loading of M deposited as MOn on the catalytic porous solid, N, in the range of 0.02 wt% to 20 wt%; c is a weight percent loading of halogen, X, deposited on MOn(d)/N in the range of 0.02 wt% to 20 wt%; b is a weight percent loading of AxByPd deposited as AxByPdOz on x ( c)/MOn(d)/N in the range of 0.1 wt% to 20 wt%; a is a weight percent loading of hydrophobic polymer, R, deposited on AxByPdOz(b)/X(c) /MOn(d)/N in the range of 0.01 wt% to 10 wt% , the said process comprises following sequential steps: (i) depositing M0n on the surface of a catalytic porous solid N, optionally deposited on a conventional catalyst carrier, by impregnating or coating N with a compound of M, wherein M is an element selected from the group consisting of S, Mo, W, Ce, Sn, or a mixture thereof, which on decomposition or calcinations converts into oxide form, in quantity sufficient to obtain a weight percent loading of M on N in the range of 0.02 wt% to 20 wt%, subsequently drying the resulting wet mass and then calcining the dried mass in air, inert gas or under vacuum at a temperature in the range 400°C to 800°C for a period in the range of 0.1 to 10 h; (ii) halogenating the mass obtained in step - I by impregnating it with one or more halogen containing compound represented by the formula: ED, wherein D is an anion selected from the group consisting of F", CI" Br", I" and (HF2)", and E is a cation selected from the group consisting of NH4+ and H+, in quantity sufficient to obtain a loading of halogen X, on the mass obtained from step - I in the range of about 0.02 wt% to about 20 wt% and subsequently drying the resulting wet mass and then calcining the dried mass in air, inert gas or under vacuum at a temperature in the range of 300°C to 600°C for a period in the range of 0.2 h to 20h; (iii) depositing AxByPdOz on the surface of the halogenated mass, obtained in step-ii, by impregnating or coating it with the compounds A, B, and Pd, wherein : A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or a mixture thereof; B is a noble metal element selected from the group consisting of Ru, Rh, Pt, Ir, Os, or their mixture; and Pd is palladium, which on decomposition or calcinations convert into their oxide form, with A/Pd and B/Pd mole ratios in the range of zero to 1.0 and zero to 0.5, respectively, and in quantities sufficient to obtain a loading of AxByPd on the mass obtained in step - ii in the range of 0.1 wt% to 20 wt%, and subsequently drying the resulting wet mass and then calcining the dried mass at temperature in the range of 350°C to 650°C in the presence of air or oxygen for a period in the range of 0.2 h to 20 h; and (iv) finally depositing a hydrophobic polymer membrane, on the surface of the catalytic mass obtained in step - iii by impregnating a hydrophobic polymer, with or without cross linking agent, from its solution in an organic solvent in quantities sufficient to obtain a loading of hydrophobic polymer on the catalytic mass in the range of 0.01 wt % to 10 wt% and subsequently removing the solvent from the polymer impregnated catalytic mass under vacuum at a temperature below 100°C and then heating the solvent - free mass in air or oxygen at a temperature in the range of 40°C to 250°C for a period in the range of 0.01 hto 10 h. The catalytic porous solid used in the catalyst preparation process of this invention may be selected from a group consisting of y - or n -alumina, silica, silica-alulmina, amorphous zirconium hydroxide, zirconium oxide, thorium oxide, uranium oxide, rare earth oxide, titanium oxide, niobium oxide, tantalum oxide, yttrium oxide, gallium oxide, indium oxide, H* form pentasil zeolites containing 5 - membered oxygen rings and having the structure of ZSM-5, ZSM-11 or ZSM - 8, H-mordenite zeolite, ultra stable HY zeolite or dealuminated HY zeolite, silicalite-l (high silica ZSM- 5) , silicalite II (high silica ZSM-11), high alumina MCM-41 zeolite, high silica MCM-41 zeolite with or without grafting by Al, Ga or transition element, an activated carbon or a mixture of two or more thereof. All these catalytic porous solids are well known in the prior art. The catalytic porous solid is optionally supported on a conventional catalyst carrier, such as monolith catalyst carriers, low surface area ( 1 Examples of the compounds of S, Mo, W, Ce, Sn, and P elements are as follows: the compounds of S are sulfuric acid and ammonium sulfate ; the compounds of P are phosphoric acid and ammonium phosphates; the compounds of Mo are ammonium molybdate and molybdenum oxide; the compounds of W are ammonium meta tungstate, tungsten oxide and tungstic acid ; the compounds of Ce are cerium(III) nitrate, cerium(III) acetate, cerium(III) hydroxide, ammonium cerium(IV) nitrate and cerium(IV) oxide; and the compounds of Sn are tin(II) nitrate, tin(II) acetate, and tin(II) oxide. Examples of the compounds of the metallic elements: Ag, Au, Cu, Fe, Cd and Zn and noble metal elements: Pd, Pt, Ru, Rh, Ir and Os are as follows: the compounds of the metallic elements are their nitrates, acetates, chlorides, hydroxides and oxides; and the compounds of the noble metal elements are their nitrates, acetates, chlorides, ammonium salts, such as ammonium hexa chloro- palladate (IV), or -platinate (IV) or -osmate (IV) or- rhodate (III) or - ruthenate (IV) or - iridate (IV), chloro acids (eg. chloro platinic acid, H2PtCl6), and the like. Examples of the hydrophobic polymer, used in step-iv of the process of this invention, are polyfluorocarbons, polysulfones, polysiloxanes or silicon rubbers, polysulfide rubbers and the like. The halogenation or halidation of the mass obtained from step-i of the process of this invention may also be done by contacting the mass with gaseous hydrogen halide or with the vapors of halohydrocarbon(s) at 100 - 500°C for a period sufficient to achieve the required weight percent loading of halogen(s) on the mass. However, the method based on the impregnation of halogen containing compounds, as discussed in step-ii of the process in this invention is preferable. In the novel catalyst and its preparation process of this invention, the roles of the various catalyst components and catalyst preparation steps are as follows. The role of the catalytic porous solid, designated by N, is to provide a support and also a highly acidic environment, after modification of its surface acidity in the first two steps [ step-i and step-ii] of the said process, for the noble and other metal oxides present in the catalyst. The catalytic porous solid is optionally supported on a conventional support, the role of which is (i) to provide mechanically strong and/or thermally stable matrix for the catalytic porous solid, (ii) to increase the dispersion and hence the surface area of the catalytic porous solid and (iii) also to reduce pressure drop across the catalyst bed, particularly for fixed bed operation of the catalyst. The role of said M0n which is incorporated in the catalyst by step-i of said process, is to increase both the number of surface acid sites and their acid strength of the catalytic porous solid used in the catalyst preparation ; for example catalytic porous solids such as alumina, zirconia, titania, silica and tin oxide by their modification by S04, WOs or MoOs are transformed into super acids. The role of halogen elements designated by X, which are incorporated in the catalyst by step-ii of said process, is also to greatly increase the surface acidity and/or change the nature of surface acidity of the catalytic porous solid used in the catalyst preparation; for example alumina, which contains only Lewis acid sites, by its modification by fluorine or chlorine containing compounds, is transformed into a protonic solid acid. The role of the palladium oxide, which is incorporated in the catalyst by step-iii of the said process, is to provide catalytically active sites, which are more selective in the acidic environment for the formation of hydrogen peroxide, for the direct oxidation of hydrogen by oxygen to hydrogen peroxide. The role of the oxides of the metallic elements (designated A) and noble metal (s) other than Pd (designated by B), which are also incorporated in the catalyst along with the palladium oxide by step-iii of the said process is to increase the hydrogen conversion activity of the catalyst in the direct oxidation of hydrogen by oxygen to hydrogen peroxide by creating synergistic effect(s). The role of the hydrophobic polymer, designated by R, which is incorporated in the catalyst by step-iv of said process, is to provide a hydrophobic character to the catalyst by forming a thin film or layer of hydrophobic polymer membrane on the catalyst, which is permeable to oxygen, hydrogen and hydrogen peroxide vapors but not to liquid water, and thereby avoiding a direct contact between the active sites present on the catalyst and the aqueous reaction medium, so that the selectivity for hydrogen peroxide formation in the direct oxidation of hydrogen by oxygen to hydrogen peroxide, in an aqueous reaction medium is drastically increased. Because of the above mentioned important roles of the components of the said catalyst, all the catalyst components and steps of their incorporation in the said catalyst by the said process are critical for achieving high hydrogen conversion with high hydrogen peroxide selectivity in the direct oxidation of hydrogen by oxygen to hydrogen peroxide in an aqueous reaction medium. In the said catalyst and its preparation process of this invention, the preferred catalytic porous solid, N, is an acidic porous solid selected from a group consisting of y- or r\|- alumina, silica-alumina, gallium oxide, cerium oxide, amorphous zirconia or zirconium hydroxide, thorium oxide, H-ZSM-5 zeolite, H-ZSM-11 zeolite, H-ZSM-8 zeolite, H-mordenite zeolite, H-MCM-41 zeolite or a mixture thereof ; the preferred M is selected from a group of element consisting of S, P, Ce or a mixture thereof ; the preferred loading of M, d, is in the range of above 0.5 wt.% to about 10 wt. % ; the preferred halogen element , X, is F, Cl or a mixture thereof; the preferred anion, D, is selected from a group consisting of F", Cl" and (HF2)~; the preferred loading of halogen element, c, is the range of about 0.5 wt% to about 10 wt% , the preferred metallic element, A , is selected from a group consisting of Au, Sn or a mixture thereof; the preferred noble metal other than Pd, B, is selected from a group consisting of Ru, Pt or a mixture thereof; the preferred A/Pd mole ratio, x , is in the range of about 0.001 to about 0.1; the preferred B/Pd mole ratio , y, is in the range of about 0.001 to about 0.1 ; the preferred loading of the metallic elements ( Ax ByPd ), b , is in the range of about 0.5 wt to about 7.5 wt%; the preferred hydrophobic polymer, R, is selected from a group consisting of polyfluorocarbons, polysiloxanes or silicone rubbers, polysulfones or a mixture thereof; and the preferred loading of hydrophobic polymer, a, is in the range of about 0.05 wt% to about 5 wt%. A number of polyfluorocarbons, polysulfones and polysiloxanes (commonly known as silicone rubbers), which are hydrophobic polymers and hence are not wetted by water or aqueous solution, are known in the prior art. Examples of polyfluorocarbons are polyvinylidine fluoride, polyvinylidine fluoride-hexaflouropropylene copolymer, polytetraflouroethylene, polychloro trifluoroethylene and polyethylene-tetrafluoroethylene copolymer. Examples of polysulfones are polysulfone, polyethersulfone, polyphenylsulfone and other hydrophobic polymer containing sulfur dioxide groups. Examples of polysiloxanes or silicone rubbers are polydimethylsiloxane, polymethylphenylsiloxane, polytrifiuoropropylmethylsiloxane and copolymers of dimethylsiloxane with methylphenylsiloxane, phenylvinylsiloxane or methylvinylsiloxane. Other examples of hydrophobia polymer are polysulfide rubbers. Among these hydrophobic polymer, i the more preferred hydrophobic polymer is selected from a group consisting of polyvinylidine fluoride, polyethersulfone, and polydimethyl siloxane containing less than 1% vinyl groups. In step (iv) of the process of this invention, the organic solvent for hydrophobic polymer may be selected from C6- C8 alkanes, benzene, toluene, xylenes, dimethyl acetamide, dimethyl formamide and dimethylsulfoxide and the cross linking agent, when used, may be trimethylol propane or benzoyl peroxide or a commercial product for example SLE 5300B obtained from GE Silicones (India) Pvt. Ltd. The catalyst prepared by the process of this invention can be used in any catalytic process for the production of hydrogen peroxide by the reaction between hydrogen and oxygen in a liquid reaction medium comprising water, with a high conversion of hydrogen and high selectivity for the hydrogen peroxide formation, even at the atmospheric pressure and room temperature. The main finding of this invention is that, because of the deposition of the hydrophobic polymer membrane on the catalyst, the selectivity for the hydrogen peroxide in the direct oxidation of hydrogen to hydrogen peroxide in a aqueous medium is increased. Other important finding of this invention is that, because of highly acidic nature of the catalyst, both the hydrogen conversion activity and selectivity for hydrogen peroxide of the catalyst in the direct oxidation of hydrogen to hydrogen peroxide are high. Another important finding of this invention is that the catalyst prepared by the process of this invention can be used for the direct oxidation of hydrogen to hydrogen peroxide even at atmospheric pressure and room temperature, giving high hydrogen conversion and high selectivity for hydrogen peroxide. The present invention is described with respect to the following examples illustrating the process of this invention for the preparation of said catalyst useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide. These examples are provided for illustrative purposes only and are not to be construed as a limitations of the said catalyst and its preparation process of this invention. Definition of terms used in the examples Conversion of H2 (%) = mole % of the hydrogen converted to all products Selectivity for H2O2 (%) = [{conversion of H2 to H202 (%)}/{conversion of H2 to all products (%)}]x 100 Yield of H2O2 (%) = mole % of H2 converted to H2O2 = [ {conversion of H2 (%)} x {selectivity for H202 (%)}]/100 The flow rate of gases are measured at 0°C and 1 atm. pressure. Gas hourly space velocity (GHSV) is a volume of gas, measured at 0°C and 1 atm. pressure, passed or bubbled through unit volume of liquid reaction medium containing catalyst per hour. Catalyst loading is defined as an amount of catalyst in gram present per dm3 of the liquid reaction medium and has a unit of g.dm"3. All the percent concentrations of solutes in their solutions are expressed as mass of solute in grams per 100ml solution. Example-1 This example illustrates the process of this invention for the preparation of a novel hydrophobic multicomponent catalyst useful for the direct oxidation of hydrogen to hydrogen peroxide. The catalyst was prepared in the following four sequential steps. Step-l:A 100 g finely powdered y -alumina (prepared by hydrolyzing aluminium isopropoxide by water at room temperature, washing the hydrolyzed mass and then drying and calcining it at 500°C for 4 h) was impregnated with a mixture of 1.6 g H2S04 (98 %) and 3.1 g Ce( N03)3. 6 H2O from their aqueous solution by the incipient wetness impregnation technique and the impregnated mass was dried in an air oven at 120°C for l0h and then calcined in an air at 600°C for 2h. Step-2: The calcined mass obtained from step-1 was impregnated with a mixture of 10 g Nt^F and 1.6 g NH4C1 by the incipient wetness impregnation technique and the impregnated mass was dried under vacuum at 80 °C for 6 h and then calcined in air at 500°C for 4h. Step-3: The calcined mass obtained from step-2 was impregnated with a mixture of 0.04 g AuCb, 0.05 g RuCh and 4.5 g PdCb from their aqueous HC1 solution by the wet impregnation technique and the impregnated mass was dried in an air oven at 100°C for 4 h and then calcined in air at 500°C for 4h. Stcp-4: Finally, the calcined catalyst mass obtained from step-3 was impregnated with 2.3 g poiyvinylidinc fluoride from its solution in dimethyl formamide solvent by the incipient wetness technique and the impregnated mass was heated first under vacuum at 90°C for 4h and then in an air at 120°C for Ih, to provide the catalyst having a composition : polyvinylidinefluoride (2.0 wt.%)/ Au 0.005 Ruo.oi PdOz (2.5 wt. % Au, Ru and Pd )/ F & Cl (6.0 wt.%)/ S Ce On (1.5 wt.% S and Ce )/ y - alumina. In the incipient wetness technique of impregnation, the volume of impregnation solution is just sufficient to completely wet the solid to be impregnated and there is no free solution in the impregnation mixture. In the wet impregnation technique, a more volume of impregnation solution than that required for completely wetting the solid to be impregnated is used and the excess of the solution present in the impregnation mixture is evaporated while stirring at about 100°C until there is no free solution is left in the impregnation mixture. ExampIe-2 This example illustrates the use of the hydrophobic multicomponent catalyst, prepared by the process of this invention in Example-1, in the direct oxidation of hydrogen by oxygen to hydrogen peroxide in aqueous reaction media at room temperature and at atmospheric pressure. The direct oxidation of hydrogen to hydrogen peroxide reaction over the catalyst was carried out in a magnetic stirred glass reactor (capacity: 300 cm3), containing 0.5 gm catalyst and 200 ml aqueous 0.016 M sulfuric acid solution as a reaction medium, by bubbling hydrogen and oxygen at a flow rate of 15 and 385 cm3.h"1, respectively, through the liquid reaction medium under vigorous stirring at room temperature (28 ± 2 °C) and atmospheric pressure (0.95 atm.) for a period of 3h. The reactor was kept in a constant temperature water bath maintained at room temperature. The temperature of the reaction medium was measured by a glass thermometer. The flow rates of hydrogen and oxygen were controlled by differential flow controllers. The flow rates of reactor effluent gases were measured by using a soap bubble flow meter. The concentration of hydrogen in the effluent gases, after removing water vapors from them by condensation at 0°C, was measured by an on-line gas chromatograph with a thermal conductivity detector, using argon as a carrier gas and 5A molecular sieve column. After stopping the reaction, the catalyst form the reaction medium was removed by filtration and the filtered reaction medium was analyzed for the hydrogen peroxide formed in the reaction by the well known iodometric titration method (Ref. A.I. Vogel, A text book of quantitative inorganic analysis, 3rd Ed., London: Longman, 1972.) The conversion of hydrogen and selectivity and yield for hydrogen peroxide in the reaction were estimated as follows. Conversion of H2 (%)= [( moles of H2 fed to the reactor) - (moles of H2 present in the reactor effluent gases)/(moles of H2 fed to the reactor)] x 100 Selectivity for H2O2 (%)= {(moles of H202 formed in the reaction)/[ (moles of H2 fed to the reactor) - (moles of H2 present in the reactor effluent gases)] } x 100 Yield of H2O2 (%) = [(moles of H2O2 formed in the reaction) / (moles of H2 fed to the reactor)] x 100 The results obtained are as follows: Conversion of H2 = 55.2% Selectivity for H2O2 = 43.3% Yield of H2O2 = 23.9% Example- 3 A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps out of which the first three steps (Steps 1-3) were exactly the same as that described in Example 1 and the forth step was as follows: Step-4: The calcined mass obtained form Step 3 was impregnated with a mixture of 3.5 gm silicone rubber (polydimethyl siloxane with less than 1% vinyl groups) and 0.35 gm trimethylol propane, which is a cross linking agent, from their solution in toluene by the incipient wetness technique and the impregnated mass was heated first under vacuum at 60°C for 4h for removing the solvent (toluene ) and then in air at 80°C for 2h for cutting the silicone rubber to provide the catalyst same as that described in Example 1 except that the hydrophobic polymer was polydimcthylsiloxane with a loading of 3.5 wt. %. Example-4 A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 1, except that, in Step 4, a polyether sulfone instead of a polyvinylidine fluoride was used as a hydrophobic polymer with a loading of 2.0 wt.%. Example-5 A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 3, except that, in the Step-4 the amount of silicone rubber used was 0.06 g instead of 3.5 g and the amount of trimethylol propane used was 0.006 g instead of 0.05g. Example-6 A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 3, except that, in the Step-2 a mixture of 1.1 g NH4F and 8.0 g NH4C1 instead of a mixture of lOg NH4F and 1.6g NH4C1 was used. Examplg-7 This example illustrates the process of this invention for the preparation of a novel hydrophobic multicomponent catalyst useful for the direct oxidation of hydrogen to hydrogen peroxide. The catalyst was prepared in the following four sequential steps. Stcp-l:A 100 g H-ZSM-5 zeolite with Si/Al mole ratio of 31.1, prepared by the method described earlier (Ref. Nayak & Choudhary, Appl. Catal. Vol. 4, page 333, year 1982) was impregnated with 7.5 g H3P04 (85%) from its aqueous solution by the incipient wetness technique and the impregnated mass was dried in an air oven at 120°C for lOh and then calcined in an air at 500°C for 6h. Stcp-2: The calcined mass obtained from step-1 was impregnated with a mixture of 5g NH4F and 3.2 g NH4C1 by the incipient wetness technique and the impregnated mass was dried under vacuum at 80°C for 6 h and then calcined in air at 500°C for 4h. Stcp-3: The calcined mass obtained from step-2 was impregnated with a mixture of 0.016 g AuCl3, 0.042 g PtCl4 and 4.5 g PdCl2 from their aqueous HC1 solution by the wet impregnation technique and the impregnated mass was dried in an air oven at 100°C for 4 h and then calcined in air at 500° C for 4h. Stcp-4: Finally, the calcined catalyst mass obtained from step-3 was impregnated with a mixture of 0.06g polydimethylsiloxane and 0.006 g trimethylol propane form their solution in toluene by the incipient wetness technique and the impregnated mass was heated first under vacuum at 90°C for 4h and then in an air at 90°C for 6h, to provide the catalyst polydimethylsiloxane (0.06 wt.%)/ Au 0.002 Pt 0005 PdOz (2.5 wt.% Au, Pt and Pd )/ F & Cl (4.5 wt.%)/ POn (2.3 wt.% P )/ H- ZSM5-5. Example-8 A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 7, except that , in the Step-3 of Example 7, the amount of PdCl2 used in this Example was 13.5g instead of 4.5g. Example-9 A novel hydrophobic multicomponent catalyst of this invention was prepared by the four consecutive steps same as that described in Example 7, except that, in the Step-3 of Example-7, the amount of PdCl2 used in this Example was 0.9g instead of 4.5g. Example-10 A novel hydrophobic multicomponent catalyst of this invention catalyst was prepared in the following four consecutive steps. Step-1: A 10 g finely powdered H-mordenite ( Z900H, obtained from M/s Norton Co., USA) was impregnated with a mixture of 0.16 g Ce( NO3)3. 6 H2O from its aqueous solution by the incipient wetness technique and the impregnated mass was dried in an air oven at 120°C for lOh and then calcined in an air at 600°C for Ih. Step-2: The calcined mass obtained from step-1 was impregnated with 1 g NH4F by the incipient wetness technique and the impregnated mass was dried under vacuum at 80°C for 6 h and then calcined in a flow of N2 (30 ml min'1) in air at 600°C for 4h. Slcp-3: The calcined mass obtained from step-2 was impregnated with a mixture of 0.006 g SnCl2.2H20, 0.009 g PtCl4 and 0.6 g Pd (N03)2 from their aqueous acidic solution by the wet impregnation technique and the impregnated mass was dried in an air oven at 100°C for 4 h and then calcined in air at 600°C for 0.5h. Stcp-4: Finally, the calcined catalyst mass obtained from step-3 was impregnated with 0.25 g polyvinylidine fluoride from its solution in dimethyl formamide solvent by the incipient wetness technique and the impregnated mass was heated first under vacuum at 90°C for 4h and then in an air at 150°C for 0.5h, to provide the catalyst polyvinylidine fluoride (2.3 wt.%)/ Sno.oiPto.oi PdOz (2.8 wt.% Sn, Pt and Pd )/ F (5 wt.%)/ CeOn (0.5 wt.% Ce )/ H-Mordenite. Example-11 A novel hydrophobic multicomponent catalyst of this invention catalyst was prepared in the following four sequential steps. Stcp-l:A 10 g finely powdered zirconium hydroxide (obtained by precipitating Zr(OH)4 from aqueous zirconyl nitrate solution by ammonium hydroxide, filtering and washing the precipitate and drying it at 200°C for 4h ) was impregnated with 0.62 g H2SO4 (98%) from its aqueous solution by the incipient wetness technique and the impregnated mass was dried in an air oven at 100°C for l0h and then calcined in an air at 650°C for 4h. Slcp-2: The calcined mass obtained from step-1 was impregnated with 0.2g NH4F by the incipient wetness technique and the impregnated mass was dried under vacuum at 120°C for 3h and then calcined in air at 500°C for lOh. Step-3: The calcined mass obtained from Step-2 was impregnated with a mixture of 0.002 g PtCU and 0.75 g PdCh from their aqueous acidic solution by the wet impregnation technique and the impregnated mass was dried in an air oven at 120°C for 4 h and then calcined in air at 600°C for 0.5h. Stcp-4: Finally, the calcined catalyst mass obtained from step-3 was impregnated with O.lg polyether sulfone from its solution in dimethyl formamide solvent by the incipient wetness technique and the impregnated mass was heated first under vacuum at 60°C for lOh and then in an air at 100°C for Ih, to provide the catalyst polyethersulfone (0.09 wt.%)/ Pt0.oo5PdOz (4.1 wt.% Pt and Pd )/ F (1.0 wt.%)/ SOn (2 wt.% S )/ ZrO2. Example-12 This example illustrates the use of the novel hydrophobic multicomponent catalyst of this invention, prepared in Examples-3-11, for the direct oxidation of Hydrogen by Oxygen to Hydrogen peroxide. The performance of the catalysts, prepared in Examples 3-11, in the catalytic process was evaluated by the procedures and at the reaction conditions same as that described in Example-2. The results obtained for the catalysts are presented in Table-1. Table-1. Results of the catalysts prepared in Examples 3-11 for the direct oxidation of H2 by O2 to H2O2.(Table Removed) Example-13 A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 11, except that , zirconium hydroxide (25 wt%) supported on a high silica MCM-41 zeolite was used instead of an unsupported zirconium hydroxide in the Step-l.The high silica MCM-41 zeolite was prepared by the procedure described earlier [Ref. V.R.Choudhary and S.D.Sansare, Proc. Indian. Acad. Sci. (Chem. Sci.) 109 (1997) 229]. The supported zirconium hydroxide was prepared by impregnating 3.7g zirconyl nitrate on 7.5g MCM-41 by drying the impregnated mass at 120°C for 4h, then impregnating the dried mass with concentrated aqueous solution of urea by the wet impregnation technique, heating the impregnated mass in a closed vessel at 80°C for 2h, filtering and washing it with deionized water, drying the mass on water bath and finally calcining it in air at 200°C for 4h to give the zirconium hydroxide supported on high silica MCM-41. Example-14 This example illustrates that the catalyst of this invention, prepared in Examples 1,3 and 4, shows higher selectivity and yield for H2O2 in the direct oxidation of hydrogen by oxygen to hydrogen peroxide than when the catalyst does not contain any hydrophobic polymer membrane. The catalytic reaction-direct oxidation of Ha by O2 to H2O2 was carried out by the procedures and at the reaction conditions same as that described in Example-2. The results are given in Table-2. Table-2. Comparison of the catalyst prepared in Examples 1, 3 and 5 with the same catalyst without any hydrophobic polymer membrane for the selectivity and yield for hydrogen peroxide in the direct oxidation of H2 by O2 to hydrogen peroxide. (Table Removed)Novel features and advantages of the catalyst of present invention over the prior art catalysts: 1) The main novel feature or advantage of the catalyst of present invention is that a hydrophobic polymer membrane, which is permeable to gases or vapors but not for liquid water or aqueous solution, is deposited on the surface of catalyst particles. Because of the hydrophobic polymer membrane, the aqueous reaction medium is not directly in contact with the active sites present on both the external and internal surface of the catalyst. The hydrogen peroxide formed by the reaction between hydrogen and oxygen over the active sites of the catalyst is diffused through the membrane and then it is absorbed in the aqueous reaction medium. Since, hydrogen peroxide has a high affinity for water and the aqueous reaction medium containing hydrogen peroxide is not in direct contact with the active sites of catalyst, the catalytic decomposition of hydrogen peroxide to water and oxygen is avoided or drastically reduced. Because of this the selectivity of hydrogen peroxide formation over the formation of water from the catalytic reaction between hydrogen and oxygen is much higher than that obtained using the prior art catalysts. 2) Because of the presence of halogen, such as fluorine with or without other halogens in the catalyst of the present invention, the surface of the catalyst also becomes atleast partially hydrophobic, which is useful for achieving higher selectivity in the formation of hydrogen peroxide from the catalytic reaction between hydrogen and oxygen. Also, because of the presence of halogen, the acidity of the catalyst is increased, making the catalyst highly acidic and thereby increasing both the activity and selectivity of the catalyst in the oxidation of hydrogen to hydrogen peroxide. 3) Unlike the prior art catalysts, the palladium element in the catalyst of this invention is present as palladium oxide, which is much more active for the oxidation of hydrogen to hydrogen peroxide than the palladium in its zero oxidation state or palladium in its metallic form. 4) The catalyst of present invention catalyses the reaction between hydrogen and oxygen producing hydrogen peroxide with a high conversion of hydrogen and a high selectivity or high yield for hydrogen peroxide, even at a pressure as low as atmospheric pressure and since the reaction using the catalyst of present invention, can be carried out at low pressures, explosion hazards are avoided. We Claim: 1. A process for the preparation of a novel hydrophobic multicomponent catalyst, comprising a hydrophobic polymer membrane, useful for the direct oxidation of H2 by O2 to hydrogen peroxide and is represented by the formula: R(a)/AxByPdOz(b)/X(c)/MOn(d)/N wherein: R is a hydrophobic polymer such as herein described , which forms a hydrophobic polymer membrane permeable to hydrogen, oxygen and hydrogen peroxide vapors; A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or a mixture thereof; B is a noble metal element other than palladium selected from the group consisting of Ru, Pt, Rh, Ir, Os, or a mixture thereof; Pd is palladium element; 0 is oxygen element; X is a halogen element selected from F, Cl, Br, I or a mixture thereof; M is an element selected from S, P, Mo, W, Ce, Sn, Th or a mixture thereof; N is a catalytic porous solid as defined herein , optionally supported on a conventional catalyst carrier; x is a A/Pd mole ratio in the range of zero to 1; y is a B/Pd mole ratio in the range of zero to 0.5 ; z is a number of oxygen atoms needed to fulfill the valence requirement of AxByPd; n is a number of the oxygen atoms needed to fulfill the valence requirement of M; d is a weight percent loading of M deposited as MOn on the catalytic porous solid, N, in the range of 0.02 wt% to 20 wt%; c is a weight percent loading of halogen, X, deposited on MOn(d)/N in the range of 0.02 wt% to 20 wt%; b is a weight percent loading of AxByPd deposited as AxByPdO2 on x ( c)/MOn(d)/N in the range of 0.1 wt% to 20 wt%; a is a weight percent loading of hydrophobic polymer, R, deposited on AxByPdOz(b)/X(c) /MOn(d)/N in the range of 0.01 wt% to 10 wt% , the said process comprises following sequential steps: (i) depositing MOn on the surface of a catalytic porous solid N, optionally deposited on a conventional catalyst carrier, by impregnating or coating N with a compound of M, wherein M is an element selected from the group consisting of S, Mo, W, Ce, Sn, or a mixture thereof, which on decomposition or calcinations converts into oxide form, in quantity sufficient to obtain a weight percent loading of M on N in the range of 0.02 wt% to 20 wt%, subsequently drying the resulting wet mass and then calcining the dried mass in air, inert gas or under vacuum at a temperature in the range 400°C to 800°C for a period in the range of 0.1 to 10 h; (ii) halogenating the mass obtained in step - I by impregnating it with one or more halogen containing compound represented by the formula: ED, wherein D is an anion selected from the group consisting of F", CI" Br", I" and (HF2)", and E is a cation selected from the group consisting of NH4+ and H, in quantity sufficient to obtain a loading of halogen X, on the mass obtained from step - I in the range of about 0.02 wt% to about 20 wt% and subsequently drying the resulting wet mass and then calcining the dried mass in air, inert gas or under vacuum at a temperature in the range of 300°C to 600°C for a period in the range of 0.2 h to 20h; (iii) depositing AxByPdOz on the surface of the halogenated mass, obtained in step-ii, by impregnating or coating it with the compounds A, B, and Pd, wherein : A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or a mixture thereof; B is a noble metal element selected from the group consisting of Ru, Rh, Pt, Ir, Os, or their mixture; and Pd is palladium, which on decomposition or calcinations convert into their oxide form, with A/Pd and B/Pd mole ratios in the range of zero to 1.0 and zero to 0.5, respectively, and in quantities sufficient to obtain a loading of AxByPd on the mass obtained in step - ii in the range of 0.1 wt% to 20 wt%, and subsequently drying the resulting wet mass and then calcining the dried mass at temperature in the range of 350°C to 650°C in the presence of air or oxygen for a period in the range of 0.2 h to 20 h; and (iv) finally depositing a hydrophobic polymer membrane, on the surface of the catalytic mass obtained in step - iii by impregnating a hydrophobic polymer, with or without cross linking agent, from its solution in an organic solvent in quantities sufficient to obtain a loading of hydrophobia polymer on the catalytic mass in the range of 0.01 wt % to 10 wt% and subsequently removing the solvent from the polymer impregnated catalytic mass under vacuum at a temperature below 100°C and then heating the solvent -free mass in air or oxygen at a temperature in the range of 40°C to 250°C for a period in the range of 0.01 h to 10 h. 2. A process as claimed in claim 1, wherein the catalytic porous solid N is a acidic porous solid selected from a group consisting of y - or r) - alumina, silica-alumina, gallium oxide, cerium oxide, amorphous zirconia or zirconium hydroxide, thorium oxide, H-ZSM - 5 zeolite, H-ZSM-11 zeolite, H-ZSM-8 zeolite, H-mordenite zeolite, H-MCM- 41 zeolite or a mixture thereof. 3. A process as claimed in claims 1-2, wherein M is selected from a group of elements consisting of S, Ce, P or a mixture thereof. 4. A process as claimed in claims 1-6, wherein the loading of halogen element, c, is in the range of 0.5 wt% to 10 wt%. 5. A process as claimed in claims 1-7, wherein the transition element, A , is selected from a group consisting of Au, Sn or a mixture thereof. 6. A process as claimed in claims 1- 8, wherein the noble metal element other than Pd, B, is selected from a group consisting of Ru, Pt or a mixture thereof. 7. A process as claimed in claims 1-9, wherein the A/Pd mole ratio, x, is in the range of 0.001 to 0.1. 8. A process as claimed in claims 1-10, wherein the B/Pd mole ratio, y, is in the range of 0.001 to 0.1. 9. A process as claimed in claims 1-11, wherein the loading of the metallic elements (AxByPd), b, is in the range of 0.5 wt% to 7.5 wt%. 10. A process as claimed in claims 1-12, wherein the hydrophobic polymer, R, is selected from a group consisting of polyfluorocarbons, polysiloxanes or silicon rubbers, polysulfones or a mixture thereof. 11. A process as claimed in claims 1-13, wherein the loading of hydrophobic polymer, a, is in the range of 0.05 wt% to 5 wt%. 12. A process for the preparation of a novel hydrophobic multicomponent catalyst, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide, substantially as herein described with reference to the examples.

Full Text

This invention relates to a novel hydrophobic multicomponent catalyst, useful for the direct oxidation of hydrogen to hydrogen peroxide, and its method of preparation. This invention particularly relates to a novel hydrophobic multicomponent catalyst comprising a hydrophobic polymer membrane deposited on a Pd containing acidic catalyst, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide, and its method of preparation.
The hydrophobic catalyst of this invention could be used in the chemical and petrochemicals industries for the production of hydrogen peroxide by direct oxidation of hydrogen by oxygen to hydrogen peroxide, which is an environmentally clean process.
Since the disclosure in U.S. patent 1,108,752 by Henkel et al. that palladium is a catalyst promoting the formation of hydrogen peroxide and water from a mixture of hydrogen and oxygen, a number of palladium containing catalysts, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide, have been disclosed by many inventors. Hydrophilic Catalysts for Direct Oxidation of H 2 by O: to Hydrogen Peroxide
A U.S. patent 4,832,938 by Gosser et al. disclosed a Pt-Pd bimetallic catalyst supported on a carbon, silica or alumina support for making hydrogen peroxide from direct combination of hydrogen and oxygen in an aqueous reaction medium. Later, a German patent Ger. Offen. DE 4,127,918 Al by Lueckoff et al. disclosed a supported palladium gold catalyst for the manufacture of hydrogen peroxide from hydrogen and oxygen in aqueous medium; the catalyst contains 5 - 95 wt % Au and is supported on carbon. A number of platinum Group metal containing catalysts: (1) Pt-Group metal on high surface area support, such as carbon, silica or alumina (Ref. U.S. patent 5,169,618); (2) Pt-Group catalyst on solid acid carrier (Ref. Eur. Pat. Appl. EP 504,741, Al); (3) Pt-Group element supported on Nb- or Ta oxide (Ref. PCT Int. Appl. WO 9,412,428 Al); (4) Sn- modified Pt-Group metals supported on catalysts carriers (Ref. Eur. Pat. Appl. EP 621,235 Al); (5) Pt-Group metal catalyst supported on hydrophilic support (Ref.

U.S. patent 5,399,334); for the oxidation of hydrogen to hydrogen peroxide are known in the prior art.
The above mentioned Pd- or Pt-Group metal containing catalysts are hydrophilic in nature, and hence the aqueous reaction medium used in the oxidation of hydrogen to hydrogen peroxide over these catalysts is in close contact with the catalyst surface. Because of the close contact between the catalyst and the reaction medium, the hydrogen peroxide, which is formed by the reaction between hydrogen and oxygen on the catalyst and then absorbed in'the reaction medium due to a high affinity between hydrogen peroxide and water, is readsorbed on the catalyst from the reaction medium and converted to water and oxygen, and thereby the selectivity for hydrogen peroxide is drastically reduced, when the above mentioned catalysts are used in the oxidation of hydrogen to hydrogen peroxide. Earlier, Fu et al. has also found that only the Pd catalysts supported on hydrophobic support are selective towards hydrogen peroxide formation in the oxidation of hydrogen [ Ref. L. Fu et al., Stud. Surf. Sci. Catal., 72(1992)33-41]. Hydrophobic Catalysts for Direct Oxidation of H: by O2 to Hydrogen Peroxide
A few Pt-Group or Group VIII metal catalysts deposited on hydrophobic support, useful for the oxidation of hydrogen to hydrogen peroxide, are also known in the prior art.
A Japanese patent Jpn. Kokai Tokkyo Koho JP 01133909 A2 by Kyora disclosed a Pt-Group metal catalyst carried on a hydrophobic support such as porous and hydrophobic Teflon support. Chuang in an European patent EP 3660419 Al disclosed a Group VIII metal catalyst deposited on a hydrophobic support for the manufacture of hydrogen peroxide by reacting hydrogen with oxygen in an aqueous medium. Later , Chuang has disclosed a Group VIII metal on a partially hydrophobic and partially hydrophilic support, such as Pd on fluorinated carbon, as a catalyst for the oxidation of hydrogen to hydrogen peroxide, in PCT Int. Appl. WO 9314025 Al. Although, the hydrophobic support used in these catalysts provides some hydrophobic

character to the Pd - or Group VIII metal catalysts, there are following disadvantages and limitations of the use of hydrophobic support for depositing the metal catalysts : 1) It is difficult to deposit catalytically active components from aqueous solution on a hydrophobic support as there is no wetting of the surface of hydrophobic support by aqueous solution. 2) Hydrophobic support, such as teflon and other hydrophobic polymer support, is thermally unstable at the calcination temperatures normally employed for decomposing the precursor compounds of catalytically active components of the catalyst. 3) Because of the deposition of catalytically active components, which are hydrophilic in nature, on hydrophobic support, the hydrophobic character of the support is lost completely or at least partially.
Apart from the above mentioned disadvantages and /or limitations, the prior art catalysts with or without hydrophobic support are employed in the oxidation of hydrogen by oxygen to hydrogen peroxide at a pressure which is much above the atmospheric pressure. At the higher
pressure, the explosion hazardous for the reaction between hydrogen and oxygen are more.
» Hence there is a need for developing a new catalyst which is active in the direct oxidation of
hydrogen to hydrogen peroxide even at atmospheric pressure and also has a hydrophobic character so that selectivity for the formation of hydrogen peroxide by the reaction between hydrogen and oxygen in an aqueous medium is high.
Accordingly, the main object of the present invention is to provide a novel hydrophobic catalyst , which is free from the above mentioned limitations, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide with high selectivity and a process for the preparation of the novel catalyst. Other object of this invention is to provide a novel hydrophobic catalyst comprising PdO in a highly acidic environment, created by a solid acid or a solid super acid, so that the catalyst shows both high activity and high selectivity in the direct oxidation of hydrogen to hydrogen peroxide. Yet another object of this invention is to provide a novel

hydrophobic multicomponent catalyst, which can be used for the direct oxidation of hydrogen to hydrogen peroxide even at atmospheric pressure, showing high hydrogen conversion activity and high selectivity for the hydrogen peroxide formation.
These and other objects are accomplished by providing a process for the preparation of a novel hydrophobic multicomponent catalyst, comprising a hydrophobic polymer membrane deposited on a highly acidic Pd containing catalyst.
Accordingly, the present invention provides a process for the preparation of a novel hydrophobic multicomponent catalyst, comprising a hydrophobic polymer membrane, useful for the direct oxidation of Ha by 02 to hydrogen peroxide and is represented by the formula:
R(a)/AxByPdOz(b)/X(c)/MOn(d)/N
wherein: R is a hydrophobic polymer, which forms a hydrophobic polymer membrane permeable to hydrogen, oxygen and hydrogen peroxide vapors; A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or a mixture thereof; B is a noble metal element other than palladium selected from the group consisting of Ru, Pt, Rh, Ir, Os, or a mixture thereof; Pd is palladium element; 0 is oxygen element; X is a halogen element selected from F, Cl, Br, I or a mixture thereof; M is an element selected from S, P, Mo, W, Ce, Sn, Th or a mixture thereof; N is a catalytic porous solid as defined herein , optionally supported on a conventional catalyst carrier; x is a A/Pd mole ratio in the range of zero to

1; y is a B/Pd mole ratio in the range of zero to 0.5 ; z is a number of oxygen atoms needed to fulfill the valence requirement of AxByPd; n is a number of the oxygen atoms needed to fulfill the valence requirement of M; d is a weight percent loading of M deposited as MOn on the catalytic porous solid, N, in the range of 0.02 wt% to 20 wt%; c is a weight percent loading of halogen, X, deposited on MOn(d)/N in the range of 0.02 wt% to 20 wt%; b is a weight percent loading of AxByPd deposited as AxByPdOz on x ( c)/MOn(d)/N in the range of 0.1 wt% to 20 wt%; a is a weight percent loading of hydrophobic polymer, R, deposited on AxByPdOz(b)/X(c) /MOn(d)/N in the range of 0.01 wt% to 10 wt% , the said process comprises following sequential steps:
(i) depositing M0n on the surface of a catalytic porous solid N, optionally deposited on a conventional catalyst carrier, by impregnating or coating N with a compound of M, wherein M is an element selected from the group consisting of S, Mo, W, Ce, Sn, or a mixture thereof, which on decomposition or calcinations converts into oxide form, in quantity sufficient to obtain a weight percent loading of M on N in the range of 0.02 wt% to 20 wt%, subsequently drying the resulting wet mass and then calcining the dried mass in air, inert gas or under vacuum at a temperature in the range 400°C to 800°C for a period in the range of 0.1 to 10 h;
(ii) halogenating the mass obtained in step - I by impregnating it with one or more halogen containing compound represented by the formula:

ED, wherein D is an anion selected from the group consisting of F", CI" Br", I" and (HF2)", and E is a cation selected from the group consisting of NH4+ and H+, in quantity sufficient to obtain a loading of halogen X, on the mass obtained from step - I in the range of about 0.02 wt% to about 20 wt% and subsequently drying the resulting wet mass and then calcining the dried mass in air, inert gas or under vacuum at a temperature in the range of 300°C to 600°C for a period in the range of 0.2 h to 20h;
(iii) depositing AxByPdOz on the surface of the halogenated mass, obtained in step-ii, by impregnating or coating it with the compounds A, B, and Pd, wherein : A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or a mixture thereof; B is a noble metal element selected from the group consisting of Ru, Rh, Pt, Ir, Os, or their mixture; and Pd is palladium, which on decomposition or calcinations convert into their oxide form, with A/Pd and B/Pd mole ratios in the range of zero to 1.0 and zero to 0.5, respectively, and in quantities sufficient to obtain a loading of AxByPd on the mass obtained in step - ii in the range of 0.1 wt% to 20 wt%, and subsequently drying the resulting wet mass and then calcining the dried mass at temperature in the range of 350°C to 650°C in the presence of air or oxygen for a period in the range of 0.2 h to 20 h; and
(iv) finally depositing a hydrophobic polymer membrane, on the surface of the catalytic mass obtained in step - iii by impregnating a hydrophobic polymer, with or without cross linking agent, from its solution in an organic solvent in quantities sufficient to obtain a loading of hydrophobic polymer on the catalytic mass in the range of 0.01 wt % to 10 wt% and subsequently removing the solvent from the polymer impregnated catalytic mass under vacuum at a temperature below 100°C and then heating the solvent - free mass in air or oxygen at a temperature in the range of 40°C to 250°C for a period in the range of 0.01 hto 10 h.
The catalytic porous solid used in the catalyst preparation process of this invention may be selected from a group consisting of y - or n -alumina, silica, silica-alulmina, amorphous zirconium hydroxide, zirconium oxide, thorium oxide, uranium oxide, rare earth oxide, titanium oxide, niobium oxide, tantalum oxide, yttrium oxide, gallium oxide, indium oxide, H* form pentasil zeolites containing 5 - membered oxygen rings and having the structure of ZSM-5, ZSM-11 or ZSM - 8, H-mordenite zeolite, ultra stable HY zeolite or dealuminated HY zeolite, silicalite-l (high silica ZSM- 5) , silicalite II (high silica ZSM-11), high alumina MCM-41 zeolite, high
silica MCM-41 zeolite with or without grafting by Al, Ga or transition element, an activated carbon or a mixture of two or more thereof. All these catalytic porous solids are well known in the prior art. The catalytic porous solid is optionally supported on a conventional catalyst carrier, such as monolith catalyst carriers, low surface area ( 1 Examples of the compounds of S, Mo, W, Ce, Sn, and P elements are as follows: the compounds of S are sulfuric acid and ammonium sulfate ; the compounds of P are phosphoric acid and ammonium phosphates; the compounds of Mo are ammonium molybdate and molybdenum oxide; the compounds of W are ammonium meta tungstate, tungsten oxide and tungstic acid ; the compounds of Ce are cerium(III) nitrate, cerium(III) acetate, cerium(III) hydroxide, ammonium cerium(IV) nitrate and cerium(IV) oxide; and the compounds of Sn are tin(II) nitrate, tin(II) acetate, and tin(II) oxide.
Examples of the compounds of the metallic elements: Ag, Au, Cu, Fe, Cd and Zn and noble metal elements: Pd, Pt, Ru, Rh, Ir and Os are as follows: the compounds of the metallic elements are their nitrates, acetates, chlorides, hydroxides and oxides; and the compounds of the noble metal elements are their nitrates, acetates, chlorides, ammonium salts, such as ammonium hexa chloro- palladate (IV), or -platinate (IV) or -osmate (IV) or- rhodate (III) or - ruthenate (IV) or - iridate (IV), chloro acids (eg. chloro platinic acid, H2PtCl6), and the like.
Examples of the hydrophobic polymer, used in step-iv of the process of this invention, are polyfluorocarbons, polysulfones, polysiloxanes or silicon rubbers, polysulfide rubbers and the like.
The halogenation or halidation of the mass obtained from step-i of the process of this invention may also be done by contacting the mass with gaseous hydrogen halide or with the vapors of halohydrocarbon(s) at 100 - 500°C for a period sufficient to achieve the required weight percent loading of halogen(s) on the mass. However, the method based on the impregnation of halogen containing compounds, as discussed in step-ii of the process in this invention is preferable.
In the novel catalyst and its preparation process of this invention, the roles of the various catalyst components and catalyst preparation steps are as follows. The role of the catalytic porous solid, designated by N, is to provide a support and also a highly acidic environment, after modification of its surface acidity in the first two steps [ step-i and step-ii] of the said process, for the noble and other metal oxides present in the catalyst. The catalytic porous solid is optionally supported on a conventional support, the role of which is (i) to provide mechanically strong and/or thermally stable matrix for the catalytic porous solid, (ii) to increase the dispersion and hence the surface area of the catalytic porous solid and (iii) also to reduce pressure drop across the catalyst bed, particularly for fixed bed operation of the catalyst. The role of said M0n which is incorporated in the catalyst by step-i of said process, is to increase both the number of surface acid sites and their acid strength of the catalytic porous solid used in the catalyst preparation ; for example catalytic porous solids such as alumina, zirconia, titania, silica and tin oxide by their modification by S04, WOs or MoOs are transformed into super acids. The role of halogen elements designated by X, which are incorporated in the catalyst by step-ii of said process, is also to greatly increase the surface acidity and/or change the nature of surface acidity
of the catalytic porous solid used in the catalyst preparation; for example alumina, which contains only Lewis acid sites, by its modification by fluorine or chlorine containing compounds, is transformed into a protonic solid acid. The role of the palladium oxide, which is incorporated in the catalyst by step-iii of the said process, is to provide catalytically active sites, which are more selective in the acidic environment for the formation of hydrogen peroxide, for the direct oxidation of hydrogen by oxygen to hydrogen peroxide. The role of the oxides of the metallic elements (designated A) and noble metal (s) other than Pd (designated by B), which are also incorporated in the catalyst along with the palladium oxide by step-iii of the said process is to increase the hydrogen conversion activity of the catalyst in the direct oxidation of hydrogen by oxygen to hydrogen peroxide by creating synergistic effect(s). The role of the hydrophobic polymer, designated by R, which is incorporated in the catalyst by step-iv of said process, is to provide a hydrophobic character to the catalyst by forming a thin film or layer of hydrophobic polymer membrane on the catalyst, which is permeable to oxygen, hydrogen and hydrogen peroxide vapors but not to liquid water, and thereby avoiding a direct contact between the active sites present on the catalyst and the aqueous reaction medium, so that the selectivity for hydrogen peroxide formation in the direct oxidation of hydrogen by oxygen to hydrogen peroxide, in an aqueous reaction medium is drastically increased.
Because of the above mentioned important roles of the components of the said catalyst, all the catalyst components and steps of their incorporation in the said catalyst by the said process are critical for achieving high hydrogen conversion with high hydrogen peroxide selectivity in the direct oxidation of hydrogen by oxygen to hydrogen peroxide in an aqueous reaction medium.
In the said catalyst and its preparation process of this invention, the preferred catalytic porous solid, N, is an acidic porous solid selected from a group consisting of y- or r|- alumina,
silica-alumina, gallium oxide, cerium oxide, amorphous zirconia or zirconium hydroxide, thorium oxide, H-ZSM-5 zeolite, H-ZSM-11 zeolite, H-ZSM-8 zeolite, H-mordenite zeolite, H-MCM-41 zeolite or a mixture thereof ; the preferred M is selected from a group of element consisting of S, P, Ce or a mixture thereof ; the preferred loading of M, d, is in the range of above 0.5 wt.% to about 10 wt. % ; the preferred halogen element , X, is F, Cl or a mixture thereof; the preferred anion, D, is selected from a group consisting of F", Cl" and (HF2)~; the preferred loading of halogen element, c, is the range of about 0.5 wt% to about 10 wt% , the preferred metallic element, A , is selected from a group consisting of Au, Sn or a mixture thereof; the preferred noble metal other than Pd, B, is selected from a group consisting of Ru, Pt or a mixture thereof; the preferred A/Pd mole ratio, x , is in the range of about 0.001 to about 0.1; the preferred B/Pd mole ratio , y, is in the range of about 0.001 to about 0.1 ; the preferred loading of the metallic elements ( Ax ByPd ), b , is in the range of about 0.5 wt to about 7.5 wt%; the preferred hydrophobic polymer, R, is selected from a group consisting of polyfluorocarbons, polysiloxanes or silicone rubbers, polysulfones or a mixture thereof; and the preferred loading of hydrophobic polymer, a, is in the range of about 0.05 wt% to about 5 wt%.
A number of polyfluorocarbons, polysulfones and polysiloxanes (commonly known as silicone rubbers), which are hydrophobic polymers and hence are not wetted by water or aqueous solution, are known in the prior art. Examples of polyfluorocarbons are polyvinylidine fluoride, polyvinylidine fluoride-hexaflouropropylene copolymer, polytetraflouroethylene, polychloro trifluoroethylene and polyethylene-tetrafluoroethylene copolymer. Examples of polysulfones are polysulfone, polyethersulfone, polyphenylsulfone and other hydrophobic polymer containing sulfur dioxide groups. Examples of polysiloxanes or silicone rubbers are polydimethylsiloxane, polymethylphenylsiloxane, polytrifiuoropropylmethylsiloxane and copolymers of dimethylsiloxane with methylphenylsiloxane, phenylvinylsiloxane or methylvinylsiloxane. Other

examples of hydrophobia polymer are polysulfide rubbers. Among these hydrophobic polymer,
i
the more preferred hydrophobic polymer is selected from a group consisting of polyvinylidine fluoride, polyethersulfone, and polydimethyl siloxane containing less than 1% vinyl groups.
In step (iv) of the process of this invention, the organic solvent for hydrophobic polymer may be selected from C6- C8 alkanes, benzene, toluene, xylenes, dimethyl acetamide, dimethyl formamide and dimethylsulfoxide and the cross linking agent, when used, may be trimethylol propane or benzoyl peroxide or a commercial product for example SLE 5300B obtained from GE Silicones (India) Pvt. Ltd.
The catalyst prepared by the process of this invention can be used in any catalytic process for the production of hydrogen peroxide by the reaction between hydrogen and oxygen in a liquid reaction medium comprising water, with a high conversion of hydrogen and high selectivity for the hydrogen peroxide formation, even at the atmospheric pressure and room temperature.
The main finding of this invention is that, because of the deposition of the hydrophobic polymer membrane on the catalyst, the selectivity for the hydrogen peroxide in the direct oxidation of hydrogen to hydrogen peroxide in a aqueous medium is increased. Other important finding of this invention is that, because of highly acidic nature of the catalyst, both the hydrogen conversion activity and selectivity for hydrogen peroxide of the catalyst in the direct oxidation of hydrogen to hydrogen peroxide are high. Another important finding of this invention is that the catalyst prepared by the process of this invention can be used for the direct oxidation of hydrogen to hydrogen peroxide even at atmospheric pressure and room temperature, giving high hydrogen conversion and high selectivity for hydrogen peroxide.
The present invention is described with respect to the following examples illustrating the process of this invention for the preparation of said catalyst useful for the direct oxidation of
hydrogen by oxygen to hydrogen peroxide. These examples are provided for illustrative purposes only and are not to be construed as a limitations of the said catalyst and its preparation process of this invention. Definition of terms used in the examples
Conversion of H2 (%) = mole % of the hydrogen converted to all products
Selectivity for H2O2 (%) = [{conversion of H2 to H202 (%)}/{conversion of H2 to all
products (%)}]x 100
Yield of H2O2 (%) = mole % of H2 converted to H2O2
= [ {conversion of H2 (%)} x {selectivity for H202 (%)}]/100
The flow rate of gases are measured at 0°C and 1 atm. pressure. Gas hourly space velocity (GHSV) is a volume of gas, measured at 0°C and 1 atm. pressure, passed or bubbled through unit volume of liquid reaction medium containing catalyst per hour.
Catalyst loading is defined as an amount of catalyst in gram present per dm3 of the liquid reaction medium and has a unit of g.dm"3.
All the percent concentrations of solutes in their solutions are expressed as mass of solute in grams per 100ml solution. Example-1
This example illustrates the process of this invention for the preparation of a novel hydrophobic multicomponent catalyst useful for the direct oxidation of hydrogen to hydrogen peroxide.
The catalyst was prepared in the following four sequential steps.
Step-l:A 100 g finely powdered y -alumina (prepared by hydrolyzing aluminium isopropoxide by water at room temperature, washing the hydrolyzed mass and then drying and calcining it at 500°C for 4 h) was impregnated with a mixture of 1.6 g H2S04 (98 %) and 3.1 g Ce( N03)3. 6
H2O from their aqueous solution by the incipient wetness impregnation technique and the impregnated mass was dried in an air oven at 120°C for l0h and then calcined in an air at 600°C for 2h.
Step-2: The calcined mass obtained from step-1 was impregnated with a mixture of 10 g Nt^F and 1.6 g NH4C1 by the incipient wetness impregnation technique and the impregnated mass was dried under vacuum at 80 °C for 6 h and then calcined in air at 500°C for 4h. Step-3: The calcined mass obtained from step-2 was impregnated with a mixture of 0.04 g AuCb, 0.05 g RuCh and 4.5 g PdCb from their aqueous HC1 solution by the wet impregnation technique and the impregnated mass was dried in an air oven at 100°C for 4 h and then calcined in air at 500°C for 4h.
Stcp-4: Finally, the calcined catalyst mass obtained from step-3 was impregnated with 2.3 g poiyvinylidinc fluoride from its solution in dimethyl formamide solvent by the incipient wetness technique and the impregnated mass was heated first under vacuum at 90°C for 4h and then in an air at 120°C for Ih, to provide the catalyst having a composition : polyvinylidinefluoride (2.0 wt.%)/ Au 0.005 Ruo.oi PdOz (2.5 wt. % Au, Ru and Pd )/ F & Cl (6.0 wt.%)/ S Ce On (1.5 wt.% S and Ce )/ y - alumina.
In the incipient wetness technique of impregnation, the volume of impregnation solution is just sufficient to completely wet the solid to be impregnated and there is no free solution in the impregnation mixture.
In the wet impregnation technique, a more volume of impregnation solution than that required for completely wetting the solid to be impregnated is used and the excess of the solution present in the impregnation mixture is evaporated while stirring at about 100°C until there is no free solution is left in the impregnation mixture.
ExampIe-2
This example illustrates the use of the hydrophobic multicomponent catalyst, prepared by the process of this invention in Example-1, in the direct oxidation of hydrogen by oxygen to hydrogen peroxide in aqueous reaction media at room temperature and at atmospheric pressure.
The direct oxidation of hydrogen to hydrogen peroxide reaction over the catalyst was carried out in a magnetic stirred glass reactor (capacity: 300 cm3), containing 0.5 gm catalyst and 200 ml aqueous 0.016 M sulfuric acid solution as a reaction medium, by bubbling hydrogen and oxygen at a flow rate of 15 and 385 cm3.h"1, respectively, through the liquid reaction medium under vigorous stirring at room temperature (28 ± 2 °C) and atmospheric pressure (0.95 atm.) for a period of 3h. The reactor was kept in a constant temperature water bath maintained at room temperature. The temperature of the reaction medium was measured by a glass thermometer. The flow rates of hydrogen and oxygen were controlled by differential flow controllers. The flow rates of reactor effluent gases were measured by using a soap bubble flow meter. The concentration of hydrogen in the effluent gases, after removing water vapors from them by condensation at 0°C, was measured by an on-line gas chromatograph with a thermal conductivity detector*, using argon as a carrier gas and 5A molecular sieve column. After stopping the reaction, the catalyst form the reaction medium was removed by filtration and the filtered reaction medium was analyzed for the hydrogen peroxide formed in the reaction by the well known iodometric titration method (Ref. A.I. Vogel, A text book of quantitative inorganic analysis, 3rd Ed., London: Longman, 1972.)
The conversion of hydrogen and selectivity and yield for hydrogen peroxide in the reaction were estimated as follows.
Conversion of H2 (%)= [( moles of H2 fed to the reactor) - (moles of H2 present in the
reactor effluent gases)/(moles of H2 fed to the reactor)] x 100
Selectivity for H2O2 (%)= {(moles of H202 formed in the reaction)/[ (moles of H2 fed
to the reactor) - (moles of H2 present in the reactor effluent gases)] } x 100
Yield of H2O2 (%) = [(moles of H2O2 formed in the reaction) / (moles of H2 fed to the
reactor)] x 100
The results obtained are as follows:
Conversion of H2 = 55.2%
Selectivity for H2O2 = 43.3%
Yield of H2O2 = 23.9% Example- 3
A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps out of which the first three steps (Steps 1-3) were exactly the same as that described in Example 1 and the forth step was as follows:
Step-4: The calcined mass obtained form Step 3 was impregnated with a mixture of 3.5 gm silicone rubber (polydimethyl siloxane with less than 1% vinyl groups) and 0.35 gm trimethylol propane, which is a cross linking agent, from their solution in toluene by the incipient wetness technique and the impregnated mass was heated first under vacuum at 60°C for 4h for removing the solvent (toluene ) and then in air at 80°C for 2h for cutting the silicone rubber to provide the catalyst same as that described in Example 1 except that the hydrophobic polymer was polydimcthylsiloxane with a loading of 3.5 wt. %.
Example-4
A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 1, except that, in Step 4, a polyether sulfone instead of a polyvinylidine fluoride was used as a hydrophobic polymer with a loading of 2.0 wt.%. Example-5
A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 3, except that, in the Step-4 the amount of silicone rubber used was 0.06 g instead of 3.5 g and the amount of trimethylol propane used was 0.006 g instead of 0.05g. Example-6
A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 3, except that, in the Step-2 a mixture of 1.1 g NH4F and 8.0 g NH4C1 instead of a mixture of lOg NH4F and 1.6g NH4C1 was used. Examplg-7
This example illustrates the process of this invention for the preparation of a novel hydrophobic multicomponent catalyst useful for the direct oxidation of hydrogen to hydrogen peroxide.
The catalyst was prepared in the following four sequential steps.
Stcp-l:A 100 g H-ZSM-5 zeolite with Si/Al mole ratio of 31.1, prepared by the method described earlier (Ref. Nayak & Choudhary, Appl. Catal. Vol. 4, page 333, year 1982) was impregnated with 7.5 g H3P04 (85%) from its aqueous solution by the incipient wetness technique and the impregnated mass was dried in an air oven at 120°C for lOh and then calcined in an air at 500°C for 6h.
Stcp-2: The calcined mass obtained from step-1 was impregnated with a mixture of 5g NH4F and
3.2 g NH4C1 by the incipient wetness technique and the impregnated mass was dried under
vacuum at 80°C for 6 h and then calcined in air at 500°C for 4h.
Stcp-3: The calcined mass obtained from step-2 was impregnated with a mixture of 0.016 g
AuCl3, 0.042 g PtCl4 and 4.5 g PdCl2 from their aqueous HC1 solution by the wet impregnation
technique and the impregnated mass was dried in an air oven at 100°C for 4 h and then calcined
in air at 500° C for 4h.
Stcp-4: Finally, the calcined catalyst mass obtained from step-3 was impregnated with a mixture
of 0.06g polydimethylsiloxane and 0.006 g trimethylol propane form their solution in toluene by
the incipient wetness technique and the impregnated mass was heated first under vacuum at 90°C
for 4h and then in an air at 90°C for 6h, to provide the catalyst polydimethylsiloxane (0.06
wt.%)/ Au 0.002 Pt 0005 PdOz (2.5 wt.% Au, Pt and Pd )/ F & Cl (4.5 wt.%)/ POn (2.3 wt.% P )/ H-
ZSM5-5.
Example-8
A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 7, except that , in the Step-3 of Example 7, the amount of PdCl2 used in this Example was 13.5g instead of 4.5g. Example-9
A novel hydrophobic multicomponent catalyst of this invention was prepared by the four consecutive steps same as that described in Example 7, except that, in the Step-3 of Example-7, the amount of PdCl2 used in this Example was 0.9g instead of 4.5g. Example-10
A novel hydrophobic multicomponent catalyst of this invention catalyst was prepared in the following four consecutive steps.
Step-1: A 10 g finely powdered H-mordenite ( Z900H, obtained from M/s Norton Co., USA) was
impregnated with a mixture of 0.16 g Ce( NO3)3. 6 H2O from its aqueous solution by the
incipient wetness technique and the impregnated mass was dried in an air oven at 120°C for lOh
and then calcined in an air at 600°C for Ih.
Step-2: The calcined mass obtained from step-1 was impregnated with 1 g NH4F by the incipient
wetness technique and the impregnated mass was dried under vacuum at 80°C for 6 h and then
calcined in a flow of N2 (30 ml min'1) in air at 600°C for 4h.
Slcp-3: The calcined mass obtained from step-2 was impregnated with a mixture of 0.006 g
SnCl2.2H20, 0.009 g PtCl4 and 0.6 g Pd (N03)2 from their aqueous acidic solution by the wet
impregnation technique and the impregnated mass was dried in an air oven at 100°C for 4 h and
then calcined in air at 600°C for 0.5h.
Stcp-4: Finally, the calcined catalyst mass obtained from step-3 was impregnated with 0.25 g
polyvinylidine fluoride from its solution in dimethyl formamide solvent by the incipient wetness
technique and the impregnated mass was heated first under vacuum at 90°C for 4h and then in an
air at 150°C for 0.5h, to provide the catalyst polyvinylidine fluoride (2.3 wt.%)/ Sno.oiPto.oi PdOz
(2.8 wt.% Sn, Pt and Pd )/ F (5 wt.%)/ CeOn (0.5 wt.% Ce )/ H-Mordenite.
Example-11
A novel hydrophobic multicomponent catalyst of this invention catalyst was prepared in the following four sequential steps.
Stcp-l:A 10 g finely powdered zirconium hydroxide (obtained by precipitating Zr(OH)4 from aqueous zirconyl nitrate solution by ammonium hydroxide, filtering and washing the precipitate and drying it at 200°C for 4h ) was impregnated with 0.62 g H2SO4 (98%) from its aqueous solution by the incipient wetness technique and the impregnated mass was dried in an air oven at 100°C for l0h and then calcined in an air at 650°C for 4h.
Slcp-2: The calcined mass obtained from step-1 was impregnated with 0.2g NH4F by the
incipient wetness technique and the impregnated mass was dried under vacuum at 120°C for 3h
and then calcined in air at 500°C for lOh.
Step-3: The calcined mass obtained from Step-2 was impregnated with a mixture of 0.002 g
PtCU and 0.75 g PdCh from their aqueous acidic solution by the wet impregnation technique
and the impregnated mass was dried in an air oven at 120°C for 4 h and then calcined in air at
600°C for 0.5h.
Stcp-4: Finally, the calcined catalyst mass obtained from step-3 was impregnated with O.lg
polyether sulfone from its solution in dimethyl formamide solvent by the incipient wetness
technique and the impregnated mass was heated first under vacuum at 60°C for lOh and then in
an air at 100°C for Ih, to provide the catalyst polyethersulfone (0.09 wt.%)/ Pt0.oo5PdOz (4.1
wt.% Pt and Pd )/ F (1.0 wt.%)/ SOn (2 wt.% S )/ ZrO2.
Example-12
This example illustrates the use of the novel hydrophobic multicomponent catalyst of this invention, prepared in Examples-3-11, for the direct oxidation of Hydrogen by Oxygen to Hydrogen peroxide. The performance of the catalysts, prepared in Examples 3-11, in the catalytic process was evaluated by the procedures and at the reaction conditions same as that described in Example-2. The results obtained for the catalysts are presented in Table-1.
Table-1. Results of the catalysts prepared in Examples 3-11 for the direct oxidation of H2 by O2 to H2O2.(Table Removed) Example-13
A novel hydrophobic multicomponent catalyst of this invention was prepared by the four sequential steps same as that described in Example 11, except that , zirconium hydroxide (25 wt%) supported on a high silica MCM-41 zeolite was used instead of an unsupported zirconium hydroxide in the Step-l.The high silica MCM-41 zeolite was prepared by the procedure described earlier [Ref. V.R.Choudhary and S.D.Sansare, Proc. Indian. Acad. Sci. (Chem. Sci.) 109 (1997) 229]. The supported zirconium hydroxide was prepared by impregnating 3.7g zirconyl nitrate on 7.5g MCM-41 by drying the impregnated mass at 120°C for 4h, then impregnating the dried mass with concentrated aqueous solution of urea by the wet impregnation technique, heating the impregnated mass in a closed vessel at 80°C for 2h, filtering and washing it with deionized water, drying the mass on water bath and finally calcining it in air at 200°C for 4h to give the zirconium hydroxide supported on high silica MCM-41. Example-14
This example illustrates that the catalyst of this invention, prepared in Examples 1,3 and 4, shows higher selectivity and yield for H2O2 in the direct oxidation of hydrogen by oxygen to hydrogen peroxide than when the catalyst does not contain any hydrophobic polymer membrane.
The catalytic reaction-direct oxidation of Ha by O2 to H2O2 was carried out by the procedures and at the reaction conditions same as that described in Example-2. The results are given in Table-2.
Table-2. Comparison of the catalyst prepared in Examples 1, 3 and 5 with the same catalyst without any hydrophobic polymer membrane for the selectivity and yield for hydrogen peroxide in the direct oxidation of H2 by O2 to hydrogen peroxide.

(Table Removed)Novel features and advantages of the catalyst of present invention over the prior art catalysts:
1) The main novel feature or advantage of the catalyst of present invention is that a hydrophobic
polymer membrane, which is permeable to gases or vapors but not for liquid water or aqueous
solution, is deposited on the surface of catalyst particles. Because of the hydrophobic polymer
membrane, the aqueous reaction medium is not directly in contact with the active sites present
on both the external and internal surface of the catalyst. The hydrogen peroxide formed by the
reaction between hydrogen and oxygen over the active sites of the catalyst is diffused through
the membrane and then it is absorbed in the aqueous reaction medium. Since, hydrogen
peroxide has a high affinity for water and the aqueous reaction medium containing hydrogen
peroxide is not in direct contact with the active sites of catalyst, the catalytic decomposition of
hydrogen peroxide to water and oxygen is avoided or drastically reduced. Because of this the
selectivity of hydrogen peroxide formation over the formation of water from the catalytic
reaction between hydrogen and oxygen is much higher than that obtained using the prior art
catalysts.
2) Because of the presence of halogen, such as fluorine with or without other halogens in the
catalyst of the present invention, the surface of the catalyst also becomes atleast partially
hydrophobic, which is useful for achieving higher selectivity in the formation of hydrogen
peroxide from the catalytic reaction between hydrogen and oxygen. Also, because of the
presence of halogen, the acidity of the catalyst is increased, making the catalyst highly acidic
and thereby increasing both the activity and selectivity of the catalyst in the oxidation of
hydrogen to hydrogen peroxide.

3) Unlike the prior art catalysts, the palladium element in the catalyst of this invention is present
as palladium oxide, which is much more active for the oxidation of hydrogen to hydrogen
peroxide than the palladium in its zero oxidation state or palladium in its metallic form.
4) The catalyst of present invention catalyses the reaction between hydrogen and oxygen
producing hydrogen peroxide with a high conversion of hydrogen and a high selectivity or high
yield for hydrogen peroxide, even at a pressure as low as atmospheric pressure and since the
reaction using the catalyst of present invention, can be carried out at low pressures, explosion
hazards are avoided.

We Claim:
1. A process for the preparation of a novel hydrophobic multicomponent catalyst, comprising a hydrophobic polymer membrane, useful for the direct oxidation of H2 by O2 to hydrogen peroxide and is represented by the formula: R(a)/AxByPdOz(b)/X(c)/MOn(d)/N
wherein: R is a hydrophobic polymer such as herein described , which forms a hydrophobic polymer membrane permeable to hydrogen, oxygen and hydrogen peroxide vapors; A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or a mixture thereof; B is a noble metal element other than palladium selected from the group consisting of Ru, Pt, Rh, Ir, Os, or a mixture thereof; Pd is palladium element; 0 is oxygen element; X is a halogen element selected from F, Cl, Br, I or a mixture thereof; M is an element selected from S, P, Mo, W, Ce, Sn, Th or a mixture thereof; N is a catalytic porous solid as defined herein , optionally supported on a conventional catalyst carrier; x is a A/Pd mole ratio in the range of zero to 1; y is a B/Pd mole ratio in the range of zero to 0.5 ; z is a number of oxygen atoms needed to fulfill the valence requirement of AxByPd; n is a number of the oxygen atoms needed to fulfill the valence requirement of M; d is a weight percent loading of M deposited as MOn on the catalytic
porous solid, N, in the range of 0.02 wt% to 20 wt%; c is a weight percent loading of halogen, X, deposited on MOn(d)/N in the range of 0.02 wt% to 20 wt%; b is a weight percent loading of AxByPd deposited as AxByPdO2 on x ( c)/MOn(d)/N in the range of 0.1 wt% to 20 wt%; a is a weight percent loading of hydrophobic polymer, R, deposited on AxByPdOz(b)/X(c) /MOn(d)/N in the range of 0.01 wt% to 10 wt% , the said process comprises following sequential steps:
(i) depositing MOn on the surface of a catalytic porous solid N, optionally deposited on a conventional catalyst carrier, by impregnating or coating N with a compound of M, wherein M is an element selected from the group consisting of S, Mo, W, Ce, Sn, or a mixture thereof, which on decomposition or calcinations converts into oxide form, in quantity sufficient to obtain a weight percent loading of M on N in the range of 0.02 wt% to 20 wt%, subsequently drying the resulting wet mass and then calcining the dried mass in air, inert gas or under vacuum at a temperature in the range 400°C to 800°C for a period in the range of 0.1 to 10 h;
(ii) halogenating the mass obtained in step - I by impregnating it with one or more halogen containing compound represented by the formula: ED, wherein D is an anion selected from the group consisting of F", CI" Br", I" and (HF2)", and E is a cation selected from the group consisting of NH4+ and H*, in quantity sufficient to
obtain a loading of halogen X, on the mass obtained from step - I in the range of about 0.02 wt% to about 20 wt% and subsequently drying the resulting wet mass and then calcining the dried mass in air, inert gas or under vacuum at a temperature in the range of 300°C to 600°C for a period in the range of 0.2 h to 20h;
(iii) depositing AxByPdOz on the surface of the halogenated mass, obtained in step-ii, by impregnating or coating it with the compounds A, B, and Pd, wherein : A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or a mixture thereof; B is a noble metal element selected from the group consisting of Ru, Rh, Pt, Ir, Os, or their mixture; and Pd is palladium, which on decomposition or calcinations convert into their oxide form, with A/Pd and B/Pd mole ratios in the range of zero to 1.0 and zero to 0.5, respectively, and in quantities sufficient to obtain a loading of AxByPd on the mass obtained in step - ii in the range of 0.1 wt% to 20 wt%, and subsequently drying the resulting wet mass and then calcining the dried mass at temperature in the range of 350°C to 650°C in the presence of air or oxygen for a period in the range of 0.2 h to 20 h; and
(iv) finally depositing a hydrophobic polymer membrane, on the surface of the catalytic mass obtained in step - iii by impregnating a hydrophobic polymer, with or without cross linking agent, from its solution in an organic solvent in quantities sufficient to obtain a
loading of hydrophobia polymer on the catalytic mass in the range of 0.01 wt % to 10 wt% and subsequently removing the solvent from the polymer impregnated catalytic mass under vacuum at a temperature below 100°C and then heating the solvent -free mass in air or oxygen at a temperature in the range of 40°C to 250°C for a period in the range of 0.01 h to 10 h.
2. A process as claimed in claim 1, wherein the catalytic porous solid
N is a acidic porous solid selected from a group consisting of y - or
r) - alumina, silica-alumina, gallium oxide, cerium oxide, amorphous
zirconia or zirconium hydroxide, thorium oxide, H-ZSM - 5 zeolite,
H-ZSM-11 zeolite, H-ZSM-8 zeolite, H-mordenite zeolite, H-MCM-
41 zeolite or a mixture thereof.
3. A process as claimed in claims 1-2, wherein M is selected from a
group of elements consisting of S, Ce, P or a mixture thereof.
4. A process as claimed in claims 1-6, wherein the loading of halogen
element, c, is in the range of 0.5 wt% to 10 wt%.
5. A process as claimed in claims 1-7, wherein the transition element,
A , is selected from a group consisting of Au, Sn or a mixture
thereof.
6. A process as claimed in claims 1- 8, wherein the noble metal
element other than Pd, B, is selected from a group consisting of
Ru, Pt or a mixture thereof.
7. A process as claimed in claims 1-9, wherein the A/Pd mole ratio,
x, is in the range of 0.001 to 0.1.
8. A process as claimed in claims 1-10, wherein the B/Pd mole ratio,
y, is in the range of 0.001 to 0.1.
9. A process as claimed in claims 1-11, wherein the loading of the
metallic elements (AxByPd), b, is in the range of 0.5 wt% to 7.5
wt%.
10. A process as claimed in claims 1-12, wherein the hydrophobic
polymer, R, is selected from a group consisting of
polyfluorocarbons, polysiloxanes or silicon rubbers, polysulfones or
a mixture thereof.
11. A process as claimed in claims 1-13, wherein the loading of
hydrophobic polymer, a, is in the range of 0.05 wt% to 5 wt%.
12. A process for the preparation of a novel hydrophobic
multicomponent catalyst, useful for the direct oxidation of hydrogen
by oxygen to hydrogen peroxide, substantially as herein described
with reference to the examples.

Documents:

273-del-1999-abstract.pdf

273-del-1999-claims.pdf

273-del-1999-correspondence-others.pdf

273-del-1999-correspondence-po.pdf

273-del-1999-description (complete).pdf

273-del-1999-form-1.pdf

273-del-1999-form-16.pdf

273-del-1999-form-2.pdf

273-del-1999-form-3.pdf

273-del-1999-petition-138.pdf

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Patent Number

215677

Indian Patent Application Number

273/DEL/1999

PG Journal Number

12/2008

Publication Date

21-Mar-2008

Grant Date

29-Feb-2008

Date of Filing

19-Feb-1999

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	DR.VASANT RAMCHANDRA CHOUDHARY	NATIONAL CHEMICAL LABORATORY, PUNE-8, INDIA.
2	DR.SUBHASH DWARKANATH SANSARE	NATIONAL CHEMICAL LABORATORY, PUNE-8, INDIA.
3	DR. ABAJI GOVINDA GAIKWAD	NATIONAL CHEMICAL LABORATORY, PUNE-8, INDIA.

PCT International Classification Number

B01J 33/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA