Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF ALKYLATED AROMATIC COMPOUNDS

Abstract

This invention relates to an improved process for the preparation of alkylated aromatic compound which comprises : i) pre-heating the catalyst prepared by the process such as herein described at a temperature in the range of 90-110°C for 10-20 h. ii) adding the catalyst to a vigorously stirred aromatic compounds such as herein described and fluxing for a period of 0.25-8 h and then diluting the suspension, iii) filtering the resultant mixture and washing the catalyst with benzene, iv) regenerating the catalyst if desired by calcining at 300-400°C for 3-6 hours and coaling to room temperature and desiccating, v) removing the solvent and recovering the alkylated aromatic compound by known methods, Reference has been made to US Patent No. 4176090.

Full Text

This invention relates to an improved process for the preparation of alkylated aromatic compound. More particularly, the prevent invention relates to an improved process for Friedel-Crafts alkylation of aromatic compounds using the alkylation catalyst prepared by the process described in our copending application No.606/Del/95. Conventional catalysts which are used in acid catalysed alkylation reactions include Bronsted acids viz. H2S04, H3PO4, 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 CP.LaszIo, Acc.Chem.Res. 19, 121 (1986), A. Cornelis et. al., Catal. Lett. 6, 103 (1990), P. Laszlo, Science, 235, 1473 (1987). However, these clays suffer from the disadvantage of layer c01 lapse when heated to above 30O°C resulting in poor performance due to decrease in surface area. [J.H. Purnell, "Pillared layer structures Current trends and applications", ed.l.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 sites. Therefore, in the preparation of clay catalyst, choice of activa- tion 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 calcination, acid activation, doping or ion-exchanging,pi1laring, supporting etc... CG.J. Ross, Clays. Clay Miner.17, 347 (1967), J.H. Clark et al., J. Chem. Soc,Chem. Comrnun. 1353 (1989), Tennakoan et al., J.C.S. Dalton, 2207(1974), M.M. Martland et al., 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)3. 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 alkylaion studied on clays are given below. a) J.H. Clark et al. CJ. Chem. Soc, Chem. Comrnun. 1353 (1989)3. reported that zinc and nickel chlorides supported on K-10 montmorillonite are highly active and selective reagents for the catalysis of Friedel-Crafts alkylations. Using 1 mmol/g loading of Zncl on K-10 (Clayzic) activated at 280oC gave 100% 2 conversion of benzyl chloride within 15 mts at room temperature. b) Friedel-Crafts alkylation of thiophene is reportedly catalysed by Montmorillonite clays modified with either Zn(II) or Fe(III) chlorides CPeter D.Clark, Andrew Kirk and Ronald Kydd., Catal. Lett., 34, 433(1987)3. High yields were obtained at 80oC ( 80%). c) P. Laszlo and A. Mathy CHelv. Chim. Acta, 70, 577 (1987)3 reported Friedel-Crafts alkylation with halides, alcohols and olefins on ion-exchanged K-10 montmori1lonite catalysts. Ti(IV) gave the best selectivity to diphenylmethane (66VS) with an overall 90% conversion of benzyl chloride. Fe(III), Cu(II), Zn(II) and Zr(IV) gave 100% conversion but selectivity was only 52-60%. Temperature was maintained at 80°C with reaction time ranging from 0.25-9 h. d) Natural Vermiculites act as highly active catalyst for Friedel-Crafts alkylation of p-methyl benzyl chloride with benzene [Shin-ichi Okada et al. Bull. Chem. Soc. Jpn., 65, 2833(1992)]. In our copending patent application No.606/Del/93, we have described and claimed a process for the production of solid acid catalysts from natural kaolins which are abundant in the clay rich states of India. The catalysts developed are efficient for aromatic alkylations studied. An object of the present invention is to provide an improved process for Friedel-Crafts alkylation of aromatic compounds. Another object is to provide an improved process for alkylation of benzene with benzyl chloride. Another object of the present invention is to provide a process for the Friedel-Craf ts alkylation employing the catalysts prepared by the process of our copending patent application No.606/Del/95. The process for the preparation of alkylation catalysts from naturally occurring clays according to the process described in our application for patent no. NF-606/Del/95 comprises : i) purifying crude clay for separating coarse minerals by sedimentation followed by wet sieving, ii) drying the bulk clay fraction of size range 90-110°C for a period of 10-20 hours, iii) calcining the resultant clay ata temperature in the range 300-600°C for 5-10 hours, iv) grinding the calcined clay, v) activating the calcined clay by treating with a mineral acid, vi) filtering the slurry and washing the resultant product with distilled water, vii) repeatedly till free from chloride ions, viii) drying the residue at a temperature of 90-110°C for 10-20 hours, ix) grinding the resultant acid treated clay, x) calcining the treated clay obtained by heating at a temperature in the range 300-600°C, for 3-6 hours and then cooling to room temperature, xi) incorporating at least one active element selected from the metals of group V-VII in the form of their compounds to acid treated clay and drying the product at a temperature & in the range of 100-I50°C for a period of 10-20 hours. All the drying and calcining steps being carried out in the presence of air or flowing oxygen and the catalysts preserved over P2O5 till use. The mineral acid employed may be selected from HCI, H2SO4 and may be of commercial 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. 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. Other important features of the catalysts are : i) activity towards Friedel-Crafts acylations and ii) decolourising action towards edible oils. Accordingly, the present invention provides an improved process for the preparation of alkylated aromatic compound which comprises : i) pre-heating the catalyst prepared by the process such as herein described at a temperature in the range of 90-110°C for 10-20 h, ii) adding the catalyst to a vigorously stirred aromatic compounds such as herein described and fluxing for a period of 0.25-8 h and then diluting the suspension, iii) filtering the resultant mixture and washing the catalyst with benzene, iv) regenerating the catalyst if desired by calcining at 300-400°C for 3-6 hours and coaling to room temperature and desiccating. v) removing the solvent and recovering the alkylated aromatic compound by known methods, The aromatic substrate serves as its own solvent. All solvents may be distilled and dried prior to use. The solvent is recovered by distillation. The solvent may be reused for alkylation.The desired product may be recovered by vacuum distillation. In a preferred embodiment of the invention the aromatic compound used may be benzene and/or benzyl chloride. The amount of benzene and benzyl chloride used may range from 10-30 %, by wt. The details of the invention is described in the Example given below which is provided by way of illustration only and should not be construed to limit the scope of the invention. Example 1 Friedel-Crafts alkylation of benzene with benzyl chloride employing the kaolin derived catalysts. Catalyst was pre-heated at a temperature in the range 90-1lOoC for 16 h. To a vigorously,stirred mixture of benzene and benzyl chloride (20:1), catalyst was added and the mixture refluxed far 0.75 h. After diluting the hot mixture with dry benzene, it was filtered and the catalyst was washed down with dry benzene. The product was separated by vacuum distillation after removing the solvent and estimated by BC and NMR methods. Catalytic activity and regenerabi1ity of kaocats are given below: (Table Removed) conversion of benzyl chloride to diphenylmethane. 73-92% monoalkylation was achieved within 45 minutes. Simple filtration separates the product from the catalyst which after washing down with solvent was regenerable by calcination. The inventian has the following advantages: i). cost effectiveness ii). high surface acidity iii). high selectivity iv). easy work-up procedure v). environmentally benign nature and vi). regenerability. We claim : 1. An improved process for the preparation of alkylated aromatic compound which comprises : i) pre-heating the catalyst prepared by the process such as herein described at a temperature in the range of 90-110°C for 10-20 h, ii) adding the catalyst to a vigorously stirred aromatic compounds such as herein described and fluxing for a period of 0.25-8 h and then diluting the suspension, iii) filtering the resultant mixture and washing the catalyst with benzene, iv) regenerating the catalyst if desired by calcining at 300-400°C for 3-6 hours and coaling to room temperature and desiccating. v) removing the solvent and recovering the alkylated aromatic compound by known methods, 2. An improved process as claimed in claim 1 wherein the aromatic compound used is benzene and/or benzyl chloride. 3. An improved process as claimed in claims 1-2 wherein the ratio of benzene and benzyl chloride is in the range of 10-30 % by wt. 4. An improved process for the preparation of alkylated aromatic compound substantially as herein described with reference to the examples.

Documents:

605-DEL-1995-Abstract.pdf

605-DEL-1995-Claims.pdf

605-DEL-1995-Correspondence-Others.pdf

605-DEL-1995-Correspondence-PO.pdf

605-DEL-1995-Description (Complete).pdf

605-DEL-1995-Form-1.pdf

605-DEL-1995-Form-2.pdf

605-DEL-1995-Form-4.pdf

605-DEL-1995-Form-9.pdf