Title of Invention

"A PROCESS FOR PREPARATION OF A HIGHLY ACIDIC MESOPOROUS SOLID CATALYSTS"

Abstract

A process for producing a highly acidic mesoporous solid catalyst comprising the hexagonal mesoporous silica having sulphated metal oxide of metal selected from the group consisting of zirconium, titanium, iron, aluminium, tin and bismuth incorporated therein, and having a surface area in the range 200-500 m2/g; a pore volume in the range of 0.1-0.3 cm3/g; a pore diameter in the range of 25-35 °A and XRD peak at 2 theta angle being 0-3, said process comprising: i. depositing water soluble salts of metals in an amount of 0.1-5.0 parts by weight into hexagonal mesoporous silica (HMS) with a pore size >13 °A in an amount of 1-10 parts by weight; ii. passing ammonia gas over the metal salt deposited HMS and thereby converting the metal salt deposits in the HMS to metal hydroxide deposits in HMS, followed by washing and drying either under vacuum at 50-100 °C or at 100-150 °C at atmospheric pressuse; iii. sulphating the metal hydroxide deposits in the HMS with at least one sulphating agent; and iv. calcining the sulphated, metal deposited HMS between 400-700 °C to thereby obtain the said catalyst.

Full Text

This invention relates to the preparation of a new ecofriendhy heterogeneous solid acid catalyst for reactions such as alkylation, acylation, oligomerization, isomerization, hydration, dehydration, etherification, esterification, hydrocracking and nitration of organic compounds with shape selectivity in the mesoporous range. The catalyst of the present invention is in the field of sulfated zirconia and mesoporous molecular sieves. Zeolites are the important family of solid acid catalysts having tridimentional crystalline aluminosilicate network with channels and cavities of molecular dimensions. The system of these molecular sieves produces materials with very high surface area and pore volume, which are capable of adsorbing great amounts of organic molecules. There has been, however, an ever growing interest in expanding the pore sizes of zeotype materials from the micropore region to mesopore region in response to the increasing demands in both industrial and fundamental studies. Mesoporous zeotype materials are inherently poor in stability and are weakly acidic. In 1992, researchers at Mobil Corporation discovered the M41S family of silicate/aluminosilicate mesoporous molecular sieves with exceptionally large uniform pore structure (Kresge, C.T. et al., Naturel992, 359. 710-712, Beck, J.S. et al., J. Am. Chem. Soc. 1992, 114. 10834-10843). This has resulted in a world-wide resurgence in this area. The template agent used is no longer a single, solvated organic molecule or metal ion, but rather self-assembled surfactant molecular arrays. The mesoporous material synthesised in the above method possesses highly regular arrays of uniform-sized channels whose diameters are in the range of 15-100°A depending on such parameters as the templates used, the addition of auxiliary organic compounds, and the reaction parameters. Synthesis of mesoporous materials has been reviewed by Tanav, P.T. and Pinnavaia, T.J. (Science, 1995, 267, 865-867). There are four general methods of preparation of mesoporous materials and any one could be used to synthesise them in the laboratory. The first three routes are based on ionic mechanisms while the fourth employs neutral templates to prepare hexagonal mesoporous molecular sieves (HMS). The last (IVth) route is based on the self-assembly between neutral primary amine micelles (S°) and inorganic precursor (Io) with hydrogen bondings. This neutral ST produces mesostructures with larger pore wall thickness and complementary textural mesoporosities, vi-a-vis those materials produced by routes I to in. The thicker pore walls improve the thermal and hydrothermal stability of the mesoporous framework. The ST pathway also allows for the facile recovery of the template by simple solvent extraction. From the above literature it can be concluded that, the preparation of mesoporous material by using the neutral templating method provides a better approach to get mesoporous materials. But, they too possess the disadvantage of very low acidity compared with other solid acid catalysts particularly for reactions requiring high acidity. With the possibility to generate active sites inside of the channels and cavities of zeolites and zeotypes, a very unique type of shape selective catalyst may be produced and it can be visualised as a catalytic microreactor. Therefore, any modification which can promote the surface acidity along with the molecular sieving property of these catalysts will be highly desirable. On the other hand, catalysts based on zirconia and other metal oxides showed very high acidity and activity when they were treated with small amount of sulfate. Hino, M; Arata, K. J. Chem. Soc., Chem. Commun., 1980, 8S1-8S2, have reported that sulfated zirconia is an acid 104 times stronger than 100% sulfuric acid and with the Hammett acidity function -Ho = 16, it is considered as the strongest halide-free solid superacid ever reported. The strong acidity makes it attractive as a catalyst in many organic reactions such as alkylation, acylation, isomerization, etherification, esterification, hydration, dehydration, oligomerisation, hydrocracking, etc. However, these superacidic materials have not found many applications because of their low surface area and non-shape selective nature. Developing a process for superacidic modified metal oxide catalyst with a high surface area along with molecular sieving capability is a challenging field to researchers. This win have applications in heavy oil cracking and Pharmaceuticals involving bulky structures. Different approaches to introduce (a)strong acidic centres into zeotype materials and (b)shape selectivity into sulfate promoted metal oxide catalysts revealed that by introducing the shape selectivity in to the oxide materials the surface area increases considerably. However, the desired activity and selectivity, could not be achieved in either case. Nor was it possible to provide the catalyst having desired activity by loading the superacids on the zeotypes. Thus the main objective of the present invention is to provide a process for preparation of a catalyst possessing high surface area, high acidity and mesoporosity. Thus according to me present invention mere is provided a process for the preparation of a highly acidic mesoporous solid catalyst "UDCaT-1" by forming insitu deposition of a metal hydroxide in a mesoporous molecular sieve (HMS) and then promoting its acidity by sulfating agents. Surprisingly the synergistic approach followed in the process of the present invention combined the benefits of superacids such as sulfated metal oxides and mesoporous zeotypes and paved the way to achieve the desired catalytic activity and selectivity. The catalyst prepared have shown promising properties in many acid catalysed organic reactions with high selectivity/specificity. In particular, in the process of invention, the HMS (one part by wt.) is taken in a reactor and the solution of metal salt (0.1-5 parts by wt.) preferably (0.5-1 parts by wt.) is added in dropwise under vigorous mixing by the incipient wetness method. The metal salt containing HMS is dried. Materials prepared by any route having mesoporous structure with pore size >13 °A such as MCM-41 can be used. Any water soluble metal salt(s) selected from the group of Zirconium, Titanium, Iron, Aluminium, Tin, Silicon, Bismuth may be used. The dried metal salt containing HMS is taken in a vertical vapour phase reactor and ammonia gas is passed through it for l-3h. It is dried at 80-150°C. It is then washed with distilled water to remove the anions. It is again dried at 80-150°C for l-3h to get the metal hydroxide deposited HMS. The sulfation of the metal hydroxide deposited HMS (the solid material) is carried out by treatment with sulfating agents such as sulfuric acid, ammonium sulfate, sulfur dioxide, sulfur trioxide and hydrogen sulfide either in solution or in gaseous phase as appropriate, preferably sulfuric acid and ammonium sulfate. The sulfated metal deposited HMS is then dried at a temperature between 100°C and 150°C and calcined at a temperature between 400°C and 750°C preferably between 500°C and 650°C. In one embodiment of the process of invention, HMS is prepared by following procedure. A primary arnine (C8-C16) used as the template (one part) is dissolved in a solvent such as aqueous alcohol (C1-C3) mixture (1:1-1:5). An alkoxide of silicon such as tetraethylorthosilicate 5-15 parts, is added under vigorous stirring. The reaction mixture is allowed for aging for 5-30 h at a temperature upto 100°C. The precipitate is separated, and dried, and calcined at a temperature between 400°C and 800°C, preferably between 500°C and 700°C to form the HMS. In an another embodiment of this HMS preparation process, the template is extracted instead of calcining, as follows. The precipitate (1 part) as prepared by following the procedure given in the above paragraph, is dried and extracted with a solvent preferably any alcohol (C1-C3), 8-15 parts, under reflux to obtain the HMS. It is dried at 80-150°C. The template recovered from me extract is preserved for reuse. In an another embodiment of the process of invention use of sulfuric acid as a sulfating agent is preferred. In this case 8-20 ml of dilute sulfuric acid (1-2N) is stirred with each gram of the solid material and the solid is separated by filtration, dried at 100-150°C and calcined at 400-750°C, preferably at 500-650°C. Examples The invention is now described by way of Examples given below which are provided by way of illustration only and should not be construed to limit the scope of the present invention. Example -1 The hexagonal mesoporous silicate (HMS) was prepared with following procedure. 5g Dodecyl amine was dissolved in 41.8g of ethanol and 29.6g of distilled water. 20.8g of tetraethyl orthosilicate was added under vigorous stirring to it. The addition of ethanol improved the solubility of the template. The reaction mixture was kept for aging for 18 hours at 30°C. The clear liquid above the white coloured precipitate was decanted and the precipitate HMS, was dried on a glass plate. The template was removed either by calcining the resulting material at 550°C in air for 3h or by refluxing the dried HMS material twice in 150 ml ethanol for 1h and drying it at 80°C in an oven for 2h. 2.5g Zirconium oxychlonde dissolved in 10ml of distilled water was added in drops to the 5g of calcined HMS with vigorous mixing. Special precaution was taken during the said procedure of addition aqueous solution of zirconium oxychlonde in calcined HMS. After every little addition of the solution, the solid was partially dried over a boiling water bath. Ultimately, after all the addition was over, the solids were dried in an oven at 120°C for Ih. The dried material was loaded in a reactor and ammonia gas was passed through it for 3h. The ammoniated sample was washed with distilled water to remove the chloride ions and dried in oven at 120°C for 2h. The sulfation was done by passing 1N sulfuric acid (15 ml/g) through the filter paper containing the dried ammoniated solid material. It was then dried in an oven for 1h at 120°C and calcined at SSO°C for 3h to give the active catalyst UDCaT-l(i). Catalyst prepared by process of Example 1 was found to be useful in Friedel-Crafts reactions and in oligomerisation of alpha olefins. Example 2 The process of Example 1 was repeated upto the stage of preparation of zirconium hydroxide insitu in HMS and then sulfation of the dried ammoniated solid material was done by using 2.5g ammonium sulfate in 6 ml distilled water instead of sulfuric acid in the sulfation step. In this case sulfation was done by wetting the dried ammoniated solid material in the ammonium sulfate solution by incipient wetness method. The sulfated material was then dried in an oven for Ih at 120°C and calcined at 550°C for 3h. This gave the active catalyst UDCaT-l(ii). WE CLAIM: 1. A process for producing a highly acidic mesoporous solid catalyst comprising the hexagonal mesoporous silica having sulphated metal oxide of metal selected from the group consisting of zirconium, titanium, iron, aluminium, tin and bismuth incorporated therein, and having a surface area in the range 200-500 m2/g; a pore volume in the range of 0.1-0.3 cm3/g; a pore diameter in the range of 25-35 0A and XRD peak at 2 theta angle being 0-3, said process comprising: depositing water soluble salts of metals in an amount of 0.1-5.0 parts by weight into hexagonal mesoporous silica (HMS) with a pore size >13 0A in an amount of 1-10 parts by weight; ii. passing ammonia gas over the metal salt deposited HMS and thereby converting the metal salt deposits in the HMS to metal hydroxide deposits in HMS, followed by washing and drying either under vacuum at 50-1 00 ~C or at 100~1 50 00 at atmospheric pressuse; iii. sulphating the metal hydroxide deposits in the HMS with at least one sulphating agent; and iv. calcining the sulphated, metal deposited HMS between 400-700 0C to thereby obtain the said catalyst. 2. A process for producing a highly acidic mesoporous solid catalyst as claimed in claim 1, wherein said calcining is carried out at between 500 and 70000. 3. A process for producing a highly acidic mesoporous solid catalyst as claimed in claims 1 or 2, wherein said sulphating agent(s) are selected from sulphuric acid, ammonium sulphate, sulphur dioxide, sulphur trioxide and hydrogen sulphide. 4. A process for producing a highly acidic mesoporous solid catalyst as claimed in claims 1 to 3, wherein the dried metal salt containing HMS is provided in a vertical vapour phase reactor and ammonia gas is passed through it for 1-3 h which is dried at 80-1 50CC for 1-3 h to obtain said metal hydroxide deposited HMS. 5. A process for producing a highly acidic mesoporous solid catalyst substantially as herein described and illustrated with reference to the accompanying examples.

Documents:

3595-del-1997-abstract.pdf

3595-DEL-1997-Claims.pdf

3595-del-1997-correspondence-others.pdf

3595-del-1997-correspondence-po.pdf

3595-del-1997-description (complete).pdf

3595-del-1997-form-1.pdf

3595-del-1997-form-19.pdf

3595-del-1997-form-2.pdf

3595-del-1997-form-4.pdf

3595-del-1997-form-6.pdf

3595-del-1997-gpa.pdf

3595-del-1997-petition-138.pdf