|Title of Invention||
"A PROCESS FOR THE PREPARATION OF MULTIMETALLIC HALIDE CATALYST".
|Abstract||A process for the preparation of multimetallic halide catalyst by mixing under stirring the composition containing 5 to 50 wt% of two or more transition metal halides and 95 to 50 wt% of clay in a non-reactive polar solvent followed by drying at a temperature in the range of 25°C to 150°C to obtain multimetallic halide catalyst.|
|Full Text||This invention relates to a composition useful for the preparation of multimetallic halide catalysts and a process for the preparation of multimetallic halide catalyst using the said composition. This invention particularly relates to clay supported multitransition-al metal halide catalysts. The catalysts prepared by the process of the present invention are useful for various catalytic reactions particularly for effecting Friedel Crafts reactions.
Supported clays employed Friedel Crafts alkylation catalysts are reported to have exceptionally high activity for the reaction of benzyl chloride with benzene to produce diphenylmethane. Clark and co-workers (Clark J. A., Kybett, A. P., Barlow D. J., and Landon P., J. Chem. .Soc. Chem. Commun., 1989, 1353-1354). had reported that clay supported zinc chloride and nickel chloride gave very good yields under very mild conditions whereas copper chloride and magnesium chloride could catalyse the reactions only very slowly. They had further reported that aluminium chloride and ferric chloride supported on clay were inactive for such reaction.
Subsequently Cornells and co-workers (Cornelis, A., Charles Dony, Laszlo, P., and Kinkela M. N., Tetrahedron Letters, 1991, 32, 1423-24) reported the inversion phenomena for a series of reactions using clayzic as the catalysts. They found that inversion of reactions rates and selectivities were obtained for the alkylation of benzylation of toluene with benzyl chloride and benzyl alcohol. Similar observations were obtained for the alkylation of benzyl chloride with benzene and toluene. They attributed this phenomena to the robotic sieving nature of clayzic type of catalyst. Yadav and co-workers (Yadav, G. D. Thorat, T. S. and Kumbhar, P. S, Tetrahedron
Letters, 1993, 34, 3, 529) had later attributed such a phenomena to the preferential adsorption of a reactant to the catalyst surface.
The hitherto known clay supported catalysts belong to the following categories.
Clay supported zinc chloride has been reported to be a very efficient catalyst for the Friedel Crafts alkylation reactions. Clayzic type of catalyst were reported to be very active for the Friedel Crafts alkylation reactions. There are lots of speculation on the activity and the reproducibility of the catalyst. Other supported catalysts such as the clay supported nickel chloride and magnesium chloride are not so active as clayzic, i.e. zinc chloride supported on, clay. All these catalyst are based on supporting single metal salt.
The lacunae in the presently available catalysts is that they take longer time to achieve the desired conversions thereby increasing the costs of production and the volume of reactors. In view of this, there is a definite need to develop new catalysts for reactions of industrial importance.
The main object of the present invention is to provide a composition useful for the preparation of multimetallic halide catalysts. Another object is to provide a process for the preparation of multimetallic halide catalyst using the said composition.
Yet another object of the present invention is to provide a process for the preparation of improved clay supported bitransitional metal halide which are useful for Friedel Crafts reactions and obviates the drawbacks of hitherto known clay based catalysts. These reactions have been found to be reproducible and highly active when compared to the use of previously known catalysts.
Accordingly the present invention provides a composition useful for the preparation of multimetallic halide catalysts which comprises :
5 to 50 wt % of two or more transition metal halides and 95 to 50 wt % of clay.
The two or more transition metal halides used may be such that one of them is an aluminium halide. The percentage of aluminium halide may be 5 to 95 wt % of the total transition metal halides used. The clay used may be untreated / treated natural clay, synthetic clay such as smectites, pyrophyllites, vermiculites, micas, kaolinites, biedellites, hectorites and pillared clay.
Accordingly the present invention provides a process for the prepara-tion of multimetallic halide catalyst using the composition as .de-scribed above which comprises mixing under stirring the composition in
a non-reactive polar solvent followed by drying at a temperature in
o o the range of 25 to 150 C.
The non-reactive polar solvent used may be such as methanol, ethanol, isopropanol, acetonitrile, n- butanol, tert-butanol and dioxane or suitable combination thereof.
The composition of the present invention is not a mere admixture but a synergistic mixture which has properties which are not a mere aggregation of the properties of the individual components and are different, resulting in catalysts which are useful for various catalytic reactions particularly for effecting Friedel Crafts reactions.
The 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 present invention.
A mixture of 0.5 gm iron chloride and 0.5 gm aluminium chloride supported on 4 gm montmorillonite clay (K-10). 0.5 gm of anhydrous ferric chloride was dissolved in 5 ml of dry methanol followed by the dissolution of 0.5 gm of aluminium chloride. This facilitates the increased solubility of aluminium chloride in the solution. Solubility of aluminium chloride is very low in methanol and it immediately forms a white coloured insoluble hydrated complex. 4 gm of dried clay was initially weighed and the solution containing both the aluminium chloride and ferric chloride was added onto the clay by the incipient wetness technique. In the incipient wetness technique the volume of solution added is equal to the pore volume of the support i.e. clay in this case. The paste formed was continuously kneaded in air to remove
methanol totally and a yellow coloured free flowing powder was ob-
o tained. This residue was then dried at 120 C for 2 hr. and stored in
an air tight container. Example 2
In a similar manner clay supported bi transitional metal halide
catalysts wherein the ratio of FeCl to A1C1 varied from 1:0, 3:1,
1:3, 0:1. Clay supported FeCl was alone called clayfec and clay
supported A1C1 alone was called clayalc. 3
The catalysts prepared by the process described in the above said examples were compared with other catalysts both commercially and synthetically preparations to check its efficacy. HPA/clay was prepared by the method given by Yadav and Kirthivasan (Yadav G. D. and Kirthivasan. N., J. Chem. Soc., Chem. Commun., 1993, 203-4). Dodecatungstophosphoric acid (20 % by weight of clay) was loaded on K-
10 montmorillonite clay by the incipient wetness technique.
Clayzic was prepared by the method adopted by Laszlo and coworkers (Laszlo, P. Cornells, A. Charles Dony. and Kinkela M. N.,
Tetrahedron Letters, 1991, 32, 2903). ZnCl (20 % by weight of mont-
morillonite clay K-10) was impregnated by a acetonitrile solution on clay by the incipient wetness technique.
A similar procedure was followed for impregnating SnCl and A1C1
on montmorillonite clay K-10. SnCl was dissolved in acetonitrile
followed by A1C1 , impregnated and activated as before (claystc). The
performance of SnCl -A1C1 supported on montmorillonite clay K-10 was.
greatly improved than when SnCl was impregnated alone on montmoril-
lonite clay K-10.
The above mentioned catalysts were tested for the reaction of benzyl chloride with benzene and toluene. The reactor consisted of a flat glass vessel of 5 cm. i.d. and 10 cm height equipped with baffles and a six blade impeller located at a height of 0.5 cm from the bottom. The assembly was kept in a water bath to maintain constant temperature. The reaction mixture could be agitated at the desired speed with the help of a variable motor.
All standard experiment was carried out by using 39.5 mmol of benzyl chloride and 197 mmol each of benzene and toluene (Laszlo, P. Cornelis, A. Charles Dony. and Kinkela M. N., Tetrahedron Letters, 1991, 32, 2903). The bitransitional metal halide catalyst Fe-Al montmorillonite clay K-10 was loaded to an extent of 11% w/w (0.55 g)
of the limiting reagent benzyl chloride. Temperature of the standard
o was maintained at 45 C. Under such conditions 100 % conversion was
observed in 45 min. The products were diphenylmethane and benzyltol-
uene. The product ratio was 1:6 as estimated by gas chromatography. A detailed kinetic study of the above reaction was done. The reaction was highly selective and no side products were formed.
Table 1 shows the comparative data of the different catalysts for their activity and selectivity towards the desired products.
COMPARATIVE ACTIVITY OF THE SUPPORTED CATALYSTS FOR THE FRIEDEL - CRAFTS ALKYLATION OF BENZYL CHLORIDE WITH BENZENE AND TOLUENE
NO CATALYST % CONVERSION PRODUCT
BnCl : 39.5mmol, toluene: 197 mmol, benzene : 197 mmol, Cat Loading :
1.5 % w/w of total reaction mixture; Temperature : 55 C. Product ratio of benzylbenzene to benzyl toluene. Figures in parantheses represent reaction time.
There is obviously a lot of difference in the activities of the cata-lysts. In all the cases the support was K-10 clay. K-10 is an com-mercial acid treated clay derived from montmorillonite. Any differ-ence in the activity could be attributed only to the reagents. ZnCl
supported on K-10 did not give such activity as was reported by Las-
zlo. Contrary to the reported facts clayfec gave better results as compared to calyzic.
Clayalc gave the least activity whereas the composite system of both aluminium chloride and ferric chloride supported on K-10 gave the best activity. Another interesting aspect was that, the activity of a single transition metal halide supported on clay gave less activity than, when two transition metal halides were supported on clay. The activity of clayfec was enhanced in the presence of aluminium chlo-ride. The effect of some electronic interaction are possible for the increase in activity of the catalyst. Sometimes the reaction was so vigorous that agitation of the reaction mixture was not required. The products of the reaction mixture were benzylbenzene and benzyltoluene. The ration of the products also varied with the change in the cata-lyst. The ratios varied from 1:4 to 1:5.5.
To check the reusability, the catalyst was subjected to the reaction once. After the reaction was complete the original contents of the reactor were decanted and fresh reactants were added to the
reaction with the once used catalyst. The above process were tested
o o when the reaction temperatures were 70 C and 55 C. The reusability
of the catalyst varied with temperature. The catalyst was reusable as
many as 4 times to the same activity at 70 C and at 55 C the
catalyst was reusable twice to the same activity and once at a reduced activity. After the catalyst had completely lost its activity then
the procedure of impregnating with FeCl alone will reactivate the
catalyst. Care should be taken that the support is thoroughly washed with acetone before impregnation. Loss of activity could be loss of the active species by leaching.
The activity of a 1:1 ratio of A1C1 and FeCl prompted us to
study the other ratios of the transition metal halides to check any
activity of the same. The other ratios of A1C1 to FeCl studied were
0:1, 1:3, 3:1, 1:0. It was found that any change in the ratios from 1:1 only suppressed the activity of the catalyst. The explain this phenomenon in a judicious manner the activity of clayalc and clayfec alone should be considered. Aluminium chloride is the best of Friedel
Crafts catalyst. However, contrary to the observed facts A1C1 when
heterogenised gave no activity. No conversion of benzyl chloride was
observed even after an hour. FeCl /K-10 showed mild activity when
compared to the composite catalyst. The presence of aluminium chloride increased the activity of the catalyst. This could be possible only if aluminium chloride occupied some of the lattice silicon thereby creating more Lewis sites.
The main advantage of the present invention is that the multime-tallic halide catalysts of the present invention are better Friedel Crafts catalysts than clays alone or single metal halide supported on clay.
We Claim :
1. A composition useful for the preparation of multimetallic halide
catalysts which comprises :
5 to 50 wt % of two or more transition metal halides and 95 to 50 wt % of clay.
2. A composition as claimed in claim 1 wherein the two or more
transition metal halides used is such that one of them is an aluminium
3. A composition as claimed in claims 1 & 2 wherein the percentage
of aluminium halide used is 5 to 95 wt % of the total transition metal
4. A composition as claimed in claims 1-3 wherein the clay used may
be untreated / treated natural clay, synthetic clay such as smectites,
pyrophyllites, vermiculites, micas, kaolinites, biedellites, hector-
ites and pillared clay.
5. A process for the preparation of multimetallic halide catalyst
using the composition as claimed in claims 1-4 which comprises mixing
under stirring the composition in a non-reactive polar solvent fol-
o o lowed by drying at a temperature in the range of 25 to 150 C.
6. A process as claimed in claim 5 wherein the non-reactive polar
solvent used may be such as methanol , ethanol, isopropanol, acetoni-
trile, n- butanol, tert-butanol and dioxane or suitable combination
7. A composition useful for the preparation of multimetallic halide
catalysts and a process for the preparation of multimetallic halide
catalyst using the said composition substantially as herein described
with reference to the examples.
|Indian Patent Application Number||433/DEL/1997|
|PG Journal Number||41/2007|
|Date of Filing||21-Feb-1997|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001, INDIA.|
|PCT International Classification Number||C07C 02/22|
|PCT International Application Number||N/A|
|PCT International Filing date|