Title of Invention

"AN IMPROVED PROCESS FOR PREPARATION OF PRIMARY ALCOHOLS"

Abstract

An improved process for the preparation of primary alcoiiols by reacting the paraffin with molecular oxygen in the presence of a solid catalyst comprising of an organotransition metal complex wherein some or all of the hydrogen atoms of the said organotransition metal complex have been substituted by one or more electron withdrawing groups, at a temperature in the range of 20°C to 100°C, at a pressure in the range of 5 to 1000 psi optionally in the presence of solvent and promoter and isolating the primary alcohols formed by conventional methods selected from fractional distillation.

Full Text

This invention relates to an improved process for the preparation of primary alcohols. More particularly the present invention relates to a process for the preparation of primary alcohols by the oxidation of normal paraffins, using molecular oxygen as the oxidant and a solid organotransition metal complex as a catalyst. Primary alcohols with 4 to 20 carbon atoms find their major applications as solvents, and as constituents in plasticizers or detergents depending on the molecular chain length and branching. These alcohols are made mainly from olefins and synthesis gas, the latter being a mixture of hydrogen and carbon monoxide, by various hydroformylation processes as provided below. Small amounts of primary alcohols are also produced by oligomerisation of ethylene followed by oxidation and hydrolysis by the Ziegler process or by methanolysis of natural oils or fats followed by hydrogenation. In the hydroformylation process, transition metal complexes of cobalt or rhodium serve as catalysts in the ligand phase in forming an aldehyde or an alcohol having one more carbon atom than the olefin feed. The aldehyde formed is later converted to the corresponding alcohol in the gas phase or in the liquid phase. The hydroformylation reaction between the olefin and the syngas is conducted in the range of 100 to 300°C and at pressures upto 300 bar. The drawbacks in the prior art processes for the manufacture of primary alcohols include : (1) The use of expensive compounds like rhodium phosphenes in the homogeneous liquid phase as catalysts necessitating their complete recovery and recycle in the process; A significant fraction of the capital investment in the plant is devoted to the recovery and recycle of these liquid phase, expensive catalysts. (2) The highly corrosive nature of the reaction medium which necessitates the use of expensive material of construction like Hastelloy for the reactor parts. (3) The use of highly toxic gases like carbon monoxide as raw material. (4) The relatively high pressures at which the hydroformylation reaction is carried out, especially when cobalt compounds are used as catalysts; (5) the use of relatively expensive olefins rather than less expensive paraffins as the raw material (6) the numerous byproducts that are formed and (7) the adverse impact on the environment during the disposal of the acid sludge caused by the liquid phase catalysts. It is thus evident that there is a need for the development of a process for the preparation of primary alcohols by the direct oxidation of the corresponding paraffins by molecular oxygen using solid, recyclable catalysts and operating at a low mi iiiijh temperature (below 100° C, for example) to avoid the production of undesirable byproducts like aldols and their condensation products. It is, therefore, an object of the present invention to provide a process for the preparation of primary alcohols by the oxidation of paraffins using a catalyst which would remain in the solid state at the end of the oxidation reaction thereby facilitating the easy separation, recovery and recycle of the catalyst from the reaction products without having any adverse impact oh the environment. Another objective of the present invention is to provide an improved process for the preparation of primary alcohols at a te-perature below 100 °C wherein a large number of byproducts due to thermal oxidation of paraffins and further aldol condensations are generated. Pthalocyanines consist of large, planar, conjugated, ring systems which serve as tetradentate ligands. Metallic cations can be easily accommodated at the center of these systems with the four nitrogens as the ligating atoms. Metal containing pthalocyanine compounds are known to be useful as chemical reagents of a catalytic nature, more particularly in directing certain oxidative processes. Many known pthalocyanines have been judged to suffer certain drawbacks by being deficient in the combination of properties desired for many candidate uses, such as in the oxidation of alkanes and more particularly in the oxidation of paraffins. One major drawback of homogeneous pthalocyanine catalysts in industrial oxidation processes is the formation of aggregates in solution which significantly deactivates these catalysts. Due to our continued research in this area we observed that the organotransition metal complexes used as catalysts are solids insoluble in paraffins or the reaction products arising from oxidation of paraffins. Hence they do not undergo aggregation or change of phase during the oxidation wherein such changes are known to lead to catalyst deactivation problems. Another drawback of pthalocyanines used in the prior art as catalysts for paraffin oxidation is their low oxidative stability which is due to the easy oxidisability of the hydrogen atoms attached to the nucleus of the pthalocyanines. We have found that the oxidative stability as well as the catalytic activity of the metal pthalocyanines used as catalysts in the oxidation of paraffins are enhanced by replacing the hydrogens from the pthalocyanines by electron withdrawing groups like the j^alogens, nitro or cyano groups thereby rendering the metal ions easier to reduce leading to an improved oxidation activity and stability of the catalysts during the reaction. There are a total of 16 hydrogen atom positions on such pthalocyanine molecules which can in principle, be substituted by other substituents. We have observed that when some or all of the hydrogen atoms of the said pthalocyanines are substituted by one or more electron withdrawing groups such as halogen, nitro or cyano groups or mixtures of such groups there is substantial improvement in selectivity and conversion to primary alcohols. Accordingly, the present invention provides an improved process for the preparation of primary alcohols which comprises reacting the paraffin with molecular oxygen in the presence of a solid catalyst comprising of an organotransition metal complex wherein some or all of the hydrogen atoms of the said organotransition metal complex have been substituted by one or more electron withdrawing groups, at a temperature in the range of 20°C to 100°C, at a pressure in the range of 5 to 1000 psi optionally in the presence of solvent and promoter and isolating the primary alcohols formed by conventional methods selected from fractional distillation. In an embodiment of the present invention the organotransition metal complex is selected from pthalocyanines and porphrins. In another embodiment of the present invention, the transition metal is selected from iron, cobalt, copper, chromium, manganese or mixtures thereof. Some nonlimiting examples of such organo transition metal complexes used as catalysts in the oxidation of cyclohexane to adipic acid are iron halopthalocyanines, copper, halo pthalocyanines, cobalt halo pthalocyanines, chromium halo pthalocyanines, manganese halo pthalocyanines, iron nitro pthalocyanines, copper nitro pthalocyanines, chromium nitro pthalocyanines, cobalt nitro pthalocyanines, manganese nitro pthalocyanines, manganese cyano pthalocyanines, copper cyano pthalocyanines and chromium cyano pthalocyanines. In yet another embodiment of present invention the electron withdrawing groups attached to the organotransition metal complex is selected from the halogens, fluorine, chlorine, bromine or iodine or the nitro or cyano groups. In a preferred embodiment of the present invention, the oxidation of paraffins by molecular oxygen is catalysed by the halogen, cyano or nitro pthalocyanines of the metals iron, cobalt, copper, chromium or manganese. In yet another embodiment of the present invention, the source of molecular oxygen can be pure oxygen gas, air or a mixture of oxygen and an inert gas diluent like nitrogen. In yet another embodiment of the present invention, the above mentioned oxidation reaction can be carried out in the presence or absence of solvents. It may be an advantageous option to carry out the said oxidation reaction in the presence of a suitable solvent which would have a high solubility for 02 and, in addition, maintain the oxidation products like primary alcohols in the dissolved state during the course of the reaction, thereby facilitating the separation of the said primary alcohols from the solid catalysts. Suitable solvents for such use include acetoni-trile, methanol, water, butanol and cyclohexanol. Examples of such solvents which can be used in the process of the present invention include acetonitrile, acetone, benzene or any other organic solvent which is inert under the oxidation reaction conditions. In another embodiment of the present invention, the rates of the oxidation of paraffins to primary alcohols may be significantly enhanced by addition of very small catalytic quantities of a promoter. Examples of such promoters include alkyl hydroperoxide, dialkylperoxides and such compounds. Cyclohexyl hydroperoxide, cumyl peroxide, tertiary butyl hydroperoxide are some of the examples of such promoters which may be present in concentrations not exceeding 1% by weight of paraffin and more preferably 0.1% by weight of paraffin. In yet another advantageous embodiment of the present invention, the organotransition metal complex may be encapsulated in a solid matrix. Due to the greater dispersion of the organotransition metal complex catalyst in solid matrices and the consequent enhanced stability of the structural integrity of the catalyst significant process advantages like greater activity, stability and easy recovery and recyclability of the catalyst are observed. Examples of such solid matrices include inorganic oxide like silica, alumina, molecular sieves, zeolites as well as organic polymeric materials, like polystyrene. In a still another embodiment of the process of the present invention that due to the high activity the catalysts used here- in, the oxidation reaction can be carried out at temeratures much below those used in the prior art and preferably below 100'C, thereby leading to much lower yields of undesired side products like ketones, dihydroxy alcohols, acids and ethers. In the process of the present invention, some aldehydes are produced, in addition to the primary alcohols. These aldehydes, may, if desired, be converted to primary alcohols by reduction processes well known in the prior art using conventional catalysts like CuO-ZnO or CuO-Si02. European Patent 97,891 describes, for example, a CuO-ZnO catalyst for the hydrogenation of butyraldehyde to butyl alcohol. The details of the present invention is described in the examples given below which are provided by way of illustration only and therefore should not be construed to limit the scope of the invention. 1 Example-1 In an autoclave, 15 g of n-hexane, 30 g of acetonitrile solvent and 0.3 g of solid copper tetra deca chloro pthalocyanine were stirred at 60 °C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-hexane, hexanol, hexanone and hexanal) which were then separated from the solid catalyst by centrifuga-tion and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A The conversion of n-hexane was 14.8% wt. The yield of 1-hexanol and 1-hexanal were 9.2 and 3.8 wt % respectively. The yield of the mixture of 2-hexanol plus 2-hexanone was 1.3 wt% Example-2 In an autoclave, 15 g of n-hexane, 30 g of acetonitrile solvent and 0.3 g of solid cobalt tetra deca fluoro pthalocyanine were stirred at 60 °C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-hexane, hexanol, hexanone and hexanal) which were then separated from the solid catalyst by centrifuga- tion and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A). 7 he results are given in Table I. Example-3 In an autoclave, 15 g of n-decane, 30 g of methanol solvent and 0.3 g of solid iron tetra nitro pthalocyanine were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unre-acted n-decane, decanol, decanone and decanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A). The results are given in Table 1. Example-4 In an autoclave, 15 g of n-decane, 30 g of acetonitrile solvent and 0.3 g of solid chromium cyano pthalocyanine were stirred at 608C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unre- acted n-decane, decanol, decanone and decanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A). u-sd-ng "5*hje results are given in Table 1. Example-5 In an autoclave, 15 g of n-cetane, 30 g of acetonitrile solvent and 0.3 g of solid manganese tetra deca chloro pthalocyanine were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-cetane, cetanol, cetanone and cetanal) which were then separated from the solid catalyst by centrifuga tion and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A). ' The results are given in Table 1. Table 1 indicates the wt % conversion of n-paraffin, wt % yield of 1-alcohol, wt % yield of 1-aldehyde and the wt % yield of 2-alcohol plus 2-ketone when using different organotransition metal complexes as catalysts and using the conditions mentioned herein above (Examples 2-5) Table 1 (Table Removed) Example-6 In an autoclave, 15 g of n-dodecane, 30 g of acetonitrile solvent and 0.3 g of solid copper tricyano pthalocyanine were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unre- acted n-dodecane, dodecanol, dodecanone and dodecanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 20 OCA)* The conversion of n-dodecane was 9.8% wt. The yield of 1-dodecanol and 1-dodecanal were 8.2 and 1.5 wt % respectively. Example-7 In an autoclave, 15 g of n-nonane, 30 g of acetonitrile solvent, 0.3 g of solid cobalt tetra deca bromo pthalocyanine and 0.08 g of tert. butyl hydroperoxide promoter were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-nonar.a, nonanol, nonanone and nonanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 n x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A). The conversion of n-nonane was 12.5% wt. The yield of 1-nonanol and 1-nonanal were 9.9 and 2.3 wt % respectively. Example-8 In an autoclave, 15 g of n-hexane, 30 g of acetonitrile solvent, 0.3 g of solid copper tetra chloro pthalocyanine encapsulated in the aluminosilicate molecular sieve-X (designated as CuCl14Pc-X) ar.d 0.0 8 g of ditert. butyl hydroperoxide promoter were stirred at £0°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unraacted n-hexane, hexanol, hexanone and hexanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone guit) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2C0:A), The conversion of n-hexane was 15.9 % wt. A The yield of 1-hexanol and 1-hexanal were 14.6 and 1.3 wt % respectively. Example-9 In an autoclave, 15 g of n-heptane, 30 g of acetonitrile solvent, 0.3 g of solid cobalt tricyano pthalocyanine encapsulated in the molecular sieve-Y and 0.08 g of tert. butyl hydroperoxide promoter were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-heptane, heptanol, heptanone and hepta-nal) which were then separated from the solid catalyst by cen-trifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2 0 00A$, The conversion of n-heptane was 9.5% wt. The yield of 1-heptanol and 1-heptanal were 8.9 and 0.3 wt % respectively. Example-10 In an autoclave, 15 g of n-heptane, 30 g of acetonitrile solvent, 0.3 g of solid iron tetra nitro pthalocyanine encapsulated in polystyrene and 0.0 8 g of tert. butyl hydroperoxide promoter were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-heptane, heptanol, heptanone and heptanal) which were then separated from the solid catalyst by centrifuga-tion and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A)A * The conversion of n-heptane was 14.6% wt. The yield of 1-heptanol and 1-heptanal were 10.1 and 2.6 wt % respectively. The yield of the mixture of 2-hexanol plus 2-hexanone was 1.8 wt *• Example-11 In an autoclave, 15 g of n-octane, 30 g of acetonitrile solvent, 0.5 g of solid copper tetra bromo porphyrin and 0.08 g of ditert. butyl hydroperoxide promoter were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-octane, octanol, octanone and octanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A)« The conversion of n-octane was 16.5% wt. ', The yield of 1-octanol and 1-octanal were 8.7 and 3.5 wt % respectively. The yield of the mixture of 2-octanol plus 2-octanone was 4 .'2 wt %. Example-12 In an autoclave, 15 g of n-butane, 30 g of acetonitrile solvent, 0.5 g of solid manganese hexachloro tetraphenyl porphyrin and 0.0 8 g of ditert. butyl hydroperoxide promoter were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unre-acted n-butane, butanol, butanone and butanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 58 8 0 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A). The conversion of n-butane was 21.2% wt. The yield of 1-butanol and 1-butanal were 16.3 and 2.9 wt % respectively. The yield of the mixture of 2-butanol plus 2-butanone was 1.7 wt %. Example-13 In an autoclave, 15 g of n-eicosane (C2QH42), 30 g of acetonitrile solvent, 0.75 g of solid manganese hexachloro tetraphenyl porphyrin encapsulated in the aluminosilicate molecular sieve-X and 0.08 g of ditert. butyl hydroperoxide promoter were stirred at 60*C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-eicosane, eicosanol, eicosanone and eicosanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector (FID). The identity of the products was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A)^ The conversion of n-eicosane was 11.6% wt. The yield of 1-eicosanol and 1-eicosanal were 10.3 and 1.2 wt % respectively. Example-14 In an autoclave, 15 g of n-hexane, 30 g of acetonitrile solvent, 1.0 g of solid CuCl14Pc-X encapsulated in polystyrene and 0.08 g of ditert. butyl hydroperoxide promoter were stirred at 60°C with a continuous bubbling of air for 8 hrs. At the end of the reaction, 10 ml of acetone was added to the products (unreacted n-hexane, hexanol, hexanone and hexanal) which were then separated from the solid catalyst by centrifugation and analysed by gas chromatography (Hewlett Packard 5880 A) using a capillary column (50 m x 0.25 mm, cross-linked methyl silicone gum) and flame ionization detector }FID). The identity of the products ^was confirmed by GC mass spectroscopy (Shimadzu GCMS-QP 2000A)J The conversion of n-hexane was 8.6 % wt. The yield of 1-hexanol and 1-hexanal were 7.8 and 0.7 wt % respectively. We claim 1. An improved process for the preparation of primary alcohols which comprises reacting the paraffin with molecular oxygen in the presence of a solid catalyst encapsulated in solid matrix as herein described comprising of an organotransition metal complex selected from pthalocyanines or porphyrins wherein some or all of the hydrogen atoms of the said organotransition metal complex have been substituted by one or mpre electron withdrawing groups selected from halogen, nitro, cyano or mixture thereof at a temperature in the range of 20°C to 100°C, at a pressure in the range of 5 to 1000 psi optionally in the presence of solvent and promoter such as herein described and isolating the primary alcohols formed by fractional distillation. 2. An improved process as claimed in claim 1 wherein the paraffin used has four to twenty carbon atoms. 3. An improved process as claimed in claims 1-2 wherein the paraffin used is normal hexane and the primary alcohol is normal hexanol. 4. An improved process as claimed in claims 1-3 wherein the normal paraffin used is dodecane and primary alcohol is dodecanol. 5. An improved process as claimed in claims 1-4 wherein the transition metal used is selected from iron, cobalt, copper, chromium, manganese or mixtures thereof. 6. An improved process as claimed in claims 1-5 wherein the source of molecular oxygen is oxygen, air or a mixture of oxygen and an inert gas nitrogen. 7. An improved process as claimed in claims 1-6 wherein tiie oxidation reaction is carried out in the presence of solvents is selected from acetonitrile, methanol, butanol or cyciohexanol. 8. An improved process as claimed in claims 1-7 wherein a promoter selected from alkyl hydroperoxide, dialkyi peroxide or mixtures thereof. 9. An improved process as claimed in claims 1-8 wherein the concentration of the promoter in the reaction mixture does not exceed 1% by weight of the normal paraffin. 10. An improved process as claimed in claims 1-9 wherein the solid matrix used is an inorganic oxide such as silica, alumina, alumino-silicates or molecular sieves selected from zeolites. 11. An improved process as claimed in claims 1-10 wherein the solid matrix is an organic polymer selected from polystyrene. 12. An improved process as claimed in claims 1-11 wherein the solid matrix contains both an inorganic oxide and an organic polymer. 13. An improved process for the preparation of primary alcohols substantially as herein described with reference to the examples.

Documents:

659-del-1996-abstract.pdf

659-del-1996-claims.pdf

659-del-1996-complete specification (granted).pdf

659-del-1996-correspondence-others.pdf

659-del-1996-correspondence-po.pdf

659-DEL-1996-Description (Complete).pdf

659-del-1996-form-1.pdf

659-del-1996-form-2.pdf

659-del-1996-form-3.pdf

659-del-1996-form-4.pdf