Title of Invention

A PROCESS FOR THE PREPARATION OF ALKYLATION CATALYSTS FROM NATURAL KAOLINITIC CLAYS

Abstract

A process for the preparation of alkylation catalyst fromnatural kaolinitic clay which comprises purifying the run-off mine clay for separating the coarse minerals by sedimentation followed by wet sieving, drying the bulk clay fraction of size <45µ at a temperature in trie range of 90- 110°C for a period of 10 to 20 hours, calcining the resultant clay at a temperature in the range of 300-600°C for 5-10 h. grinding the calcined clay by known methods, activating the calcined clay by treating with 0:1-6 M mineral acid for 0.25-8 h, filtering the slurry and washing the resultant product repeatedly with water till free from chloride ions, drying the residue obtained at a temperature of 90-110°C for 10-20 h, grinding the resullnat acid treated clay, calcining the treated clay obtained at a temperature in the range of 300- 600°C for 3-6 h and then cooling to room temperature, incorporating at least one active element selected from the metals of group V-VIII in the form of their compound as herein described to the acid treated clay and drying the product at 100-150"C for 10-20 h to obtain alkylation catalyst.

Full Text

This invention relates to a process for the preparation of alkylation catalyst from natural kaolinitic clay. Conventional catalysts which are used in acid catalysed alkylation reactions include Bronsted acids viz. H2S04, H3P04, HF as well as usual Lewis acids such as metallic halides (AICI3, GaCI3, FeCI3, BCI3, BF3 etc.) [G.A.OIah, Friedel-Crafts and related reactions, Vol.2, Part 1, 1 (1964)]. Apart from being potent health hazards, the above catalysts cause tedious work-up procedures. Also, polyalkylations and rearrangements are often difficult to avoid. Clays and related catalysts have been widely employed in fine chemical synthesis, the most extensively studied being the montmorillonite variety of clays [P. Laszio, Ace. Chem. Res. 19, 121 (1986), A. Cornelis et. AL. Cata]. Lett. 6. 103 (1990), P. Laszio, Science, 235, 1473 (1987). However, these clays suffer from the disadvantage of layer collapse when heated to above 300oC resulting in poor performance due to decrease in surface area. [J.H. Furnell, "Pillared layer structures : Current trends and applications", ed. I.V. Mitchell, Elsevier Applied Science, 107 (1990)]. It is well known that Friedel-Crafts alkylations on solid acids are catalysed by Bronsted acid as well as Lewis acid sties. Therefore, in the preparation of clay catalyst, choice of activation is a key factor. Various methods of pretreatment of clay and post modifications of the derived catalysts are reported in literature. These include techniques like calcinations, acid activation, doping or ion-exchanging, pillaring, supporting etc. [G.J. Boss, Clays. Clay Miner 17, 347 (1967), J.H. Clark et. Al., J. Chem. Soc, Chem. Commun. 1353 (1989), Tennakoon et. Al., J.C.S. Dalton, 2207 (1974), M.M. Mortland et. Al.m Clays. Clay, Miner, 24, 60 (1976), D.E.W. Vaughan et. Al., German Patent 2, 825, 769 (1979), d.E.W. Vaughan et. Al., U.S. Patent 4,176.090 (1979)]. However the potential utility of kaolinitic clays (kaolins) as catalysts have not been studied in detail. A few prior art references regarding the Friedel-Crafts alkylation studied on clays are given below : a) J.H. Clark et. Al. [J. Chem. Soc. Lhem. Commun. 1353 (1989)]. Reported that zinc and nickel chlorides supported on K-10 montmorillonite are highly active and selective reagents for the catalysis of Friedel-Crafts aikylations. Using 1 mmol/g loading on Zncl2 on K-10 (Clayzic) activated at 280oC gave 100% conversion of benzyl chloride within 15 mts at room temperature, b) Friedel-Crafts aikylation of thiophene is reportedly catalysed by Montmoriltonite clays modified with either Zn(ll) or Fe(lll) chlorides [Peter D. Clark, Andrew Kirk and Ronald Kydd., Catal. Lett, 34, 433 (1987)]. High yields were obtained at 80oC (80%), c) P. Laszlo and A. Mathy [Helv. Chim. Acta, 70, 577 (1987)] reported Friedel-Crafts aikylation with halides, alcohols and olefins on ion-exchanged K-10 montmorillonite catalysts. Ti(IV) gave the best selectivity to diphenylmethane (66%) with an overall 90% conversion of benzyl chloride. Fe(lll), Cu(ll), Zn(ll) and Zr(IV) gave 100% conversion but selectivity was only 52-60%. Temperature was maintained at 80oC with reaction time ranging from 0.25-9 h. d) Natural Vermiculites act as highly active catalyst for Friedel-Crafts aikylation of p- methyl benzyl chloride with benzene [Shin-ichi Okada et al. Bull. Chem.Soc. Jpn., 65, 2833(1992)]. The main object of the present invention is to provide a process for the preparation of aikylation catalysts based on natural kaolins. The catalysts prepared are designated as "Kaocats".They are strongly acidic (H , -8.2), relatively cheap and above all, possess the salient features of an "eco-friendly" catalyst, the most important being its non-corrosive nature. According to the present invention the solid acid catalysts are prepared from natural kaolins which are abundant in the clay rich states of India. The catalysts prepared are efficient for aromatic aikylations studied. Process for the preparation of such catalysts has not been reported in India or abroad to the best of our knowledge. The catalyst prepared by the process of the present invention is useful for Friedel-Crafts aikylation of benzene with benzyl chloride. Therefore, it is a definite substitute for the conventional catalysts employed in such fine chemical synthesis. Also the catalyst is regenerable. The spent catalyst was found to retain its activity even after 5 successive regeneration cycles. Accordingly, the present invention provides a process for the preparation of alkylation catalyst from natural kaolinitic clay which comprises : i) purifying the run-off mine clay for separating the coarse minerals by sedimentation followed by wet sieving, ii) drying the bulk clay fraction of size for a period of 10 to 20 hours, iii) calcining the resultant clay at a temperature in the range of 300-600°C for 5-10 h, iv) grinding the calcined clay by known methods, v) activating the calcined clay by treating with 0.1-6 M mineral acid for 0.25-8 h, vi) filtering the slurry and washing the resultant product repeatedly with water till free from chloride ions, vii) drying the residue obtained at a temperature of 90-110°C for 10-20 h, viii) grinding the resultnat acid treated clay, ix) calcining the treated clay obtained at a temperature in the range of 300-600°C for 3-6 h and then cooling to room temperature, x) incorporating at least one active element selected from the metals of group V-VIII in the form of their compound as herein described to the acid treated clay and drying the product at 100-150°C for 10-20 h to obtain alkylation catalyst. All the drying and calcining steps being carried out in the presence of air or flowing oxygen and the catalysts preserved over P205 till use. vi) filtering the slurry and washing the resultant product repeatedly with water till free from chloride ions, vii) drying the residue obtained at a temperature of 90-110°C for 10-20 h, viii) grinding the resultnat acid treated clay, ix) calcining the treated clay obtained at a temperature in the range of 300- 600°C for 3-6 h and then cooling to room temperature, x) incorporating at least one active element selected from the metals of group V-VTll in the form of their compound as herein described to the acid treated clay and drying the product at 1Q0-150°C for 10-20 h to obtain alkyiation catalyst. All the drying and calcining steps being carried out in the presence of air or flowing oxygen and the catalysts preserved over P205 tilt use. The mineral acid employed may be selected from -HCl, H2SO4 and may be of commercia! grade. The concentration of such acid may be in the range of 0.1-6 M. The solid-liquid ratio may vary between 1:2 and 1:50 but preferably 1:4. Activation of the catalyst was effected under reflux conditions and atmospheric pressure. Recovery of the clay from suspension can be effected by repeated centrifugation and decantation till the supernatant liquid was free from chloride ions. In view of the suitability of the surface acidity of kaolin-derived catalysts, we have successfully carried out the Friedel-Crafts alkyiation using these catalyts. The catalyst is efficient in converting benzyl chloride to diphenylmethane with 100% selectivity. 73-92% monoalkylation is achieved in less than 45 minutes at reflux conditions. Such a process has been made the subject matter of copending application No.605/Del/95. Other important features of the catalysts are : i) activity towards Friedel-Crafts acylations and, ii) decolourising action towards edible oils. 'The details of the invention is described in the Examples given below which are provided by way of illustration only and should not. be construed to limit the scope of the invention. Example-T Kaolin was purified by suspending the crude lumps in water (500 g in 5 dm"3 water) by vigorous stirring and allowing the coarser minerals to settle. Suspended clay minerals were siphoned off through 45 0181 sieve and the Exampie-2 Kaolin was purified by suspending the crude lumps in water (500 g in 5 dm"5 water) by vigorous stirring and allowing the coarser particles to settle. Suspended clay minerals were siphoned off through 45 µ sieve and Iho 46 µ sizo fraction collected and dried at 90-110"C for 16 h. The clay was calcined at 500°C for 6 h. The calcined clay was powdered and then acid 'activated by treating with 1.5 M HCI for 0.75 h under reflux conditions. The treated clay was then filtered and the residue repeatedly washed with distilled water till free from chloride ions. The catalyst was oven driod at 90-11 D°C for 16 h, powdered and then cafc/ned at 400°C for 3 h, cooled down to room temperature and stored over P:?05. Example 3 Kaolin was purified by suspending the crude lumps in water (500 g in dm-0 water) by vigorous stirring and allowing the coarser particles to settle. Suspended clay minerals were siphoned off through 45u sieve and the Chemical assay and X-ray diffractc-gram (XRD) characteristics: (Table Removed) Composition and the structure of the clay mineral were determined by chemical as well as XRD analysis. It was found that the chief mineral constituent was kaolinite as shown in the XRD patterns in Fig.1-3 (sheet no. 1-3) of the drawings accompanying this specification for three typical samples Kaolin A, Kaolin B and Kaolin C, the modifications of which are illustrated in Example 1, Example 2 and Example 3 respectively. Fig. 1 X-ray diffraction pattern of Fig. 2 X-ray diffraction pattern of Fig. 3 X-ray diffraction pattern of ('#" denotes kaolinite peaks). Chemical characteristics of kaolins and the corresponding catalysts (kaocats) prepared from them are as given below: * determined at 1025±25*C It is evident that considerable amount of aluminium has been leached out from all samples by the combined process of calcination and acid activation.Also, X-ray diffractograms showed conclusive layer collapse of kaolin in all the three cases. All the interlayer cations are replaced by H by acid treatment. Isoroorphously substituted Fe and Ti can also leach out in this way. The relocation of the leached out Al, Fe and Ti cations in the partially collapsed interlayer space is possible. These relocated cations can have co-ordination with interstitial water molecules rendering them better proton donors resulting in high acidity of the material. Surface, area was measured by BET method and surface acidity was determined by Benesi method. Surface area was enhanced considerably which receives contribution from the partial layer collapse as well as the porosity created by the combined processes of calcination and acid activation. Kaocats exhibited strong acidity even higher than that required normally to catalyse Friedel-Crafts alkylations ie... H0 Surface area and acidity distribution of kaolins and kaocats: Surface Butyl amine titer (mmol/g) in the H0 range Sample area (Table Removed) * Titer uncertainty is 0.01 mmole/g. In view of the significant surface acidity of the kaocats created by the activation processes, we employed the developed catalysts in the Friedel-Crafts alkylation of benzene using benzvl chloride. claim : 1. A process for the preparation of alkylation catalyst from natural kaolinitic clay which comprises : i) purifying the run-off mine clay for separating the coarse minerals by sedimentation followed by wet sieving, ii) drying the bulk clay fraction of size 110°C for a period of 10 to 20 hours, iii) calcining the resultant clay at a temperature in the range of 300-600°C _ for 5-10 h, iv) grinding the calcined clay by known methods, v) activating the calcined clay by treating with 0.1-6 M mineral acid for 0.25-8 h, vi) filtering the slurry and washing the resultant product repeatedly with water till free from chloride ions, vii) drying the residue obtained at a temperature of 90-110°C for 10-20 h, viii) grinding the resultnat acid treated clay, ix) calcining the treated clay obtained at a temperature in the range of 300- 600°C for 3-6 h and then cooling to room temperature, x) incorporating at least one active element selected from the metals of group V-Vlll in the form of their compound as herein described to the acid treated clay and drying the product at 100-150°C for 10-20 h to obtain alkylation catalyst. A process as claimed in claim 1 wherein the mineral acid used is HCI, H2S04. A process as claimed in claims 1-2 wherein the solid-liquid ratio during acid treatment is in the range of 1:2-1:50, A process as claimed in claims 1-3 wherein the drying and the calcining steps being carried out in the presence of air or flowing oxygen. A process for the preparation of alkylation catalyst from natural kaolinitic clay substantially as herein described with reference to the examples.

Documents:

606-del-1995-abstract.pdf

606-del-1995-claims.pdf

606-del-1995-correspondence-others.pdf

606-del-1995-correspondence-po.pdf

606-del-1995-description (complete).pdf

606-del-1995-drawings.pdf

606-del-1995-form-1.pdf

606-del-1995-form-2.pdf

606-del-1995-form-4.pdf

606-del-1995-form-9.pdf