Title of Invention

" AN IMPROVED PROCESS FOR THE PRODUCTION OF EPICHLOROHYDRIN"

Abstract

An improved process for the production of epichlorohydrin (ECH) which comprises reacting a mixture comprising allylchlonde, aqueous hydrogen peroxide in the range of 10 to 70% and a surfactant as defined herein, with a solid titanium silicate zeolite catalyst at a temperature ranging between 10-60° C , collecting the product after the reaction, demulsifying it by adding aqueous saturated salt solution, phase separating the product along with unconverted reactant, if any, and purifying the product(s) present in the organic layer by using conventional method as herein described , the said process characterized in using the said titanium silicate zeolite catalyst and aqueous hydrogen peroxide.

Full Text

This invention relates to an improved process for the production of epichlorohydrin, hereinafter referred to as ECH. More particularly, it relates to the oxidation of allylchloride, hereinafter referred to as ALC, producing ECH using a solid catalyst and an oxidizing agent. ECH is used as an intermediate in the preparation of resins, Pharmaceuticals products and pesticides. Apart from these important uses, ECH is commonly used as synthon by synthetic organic chemists. Commercially, ECH is manufactured by reacting ALC with chlorinewater followed by lime treatment. However, this non-catalytic process produces large quantities of sludge (calcium chloride) which needs to be disposed off, creating severe environmental problem. One more dnvback of the conventional procedure is its low selectivity for ECH (-70%), the remaining products being low valued chlorohydrines. Other method of preparation of ECH involves oxidation of ALC in presence ol" transition metal oxides and organic peroxide. The alternative method has met with little success due to slow rates and competing reactions, such as the homolytic decomposition of the oxidant and the solvolysis of the oxirane ring resulting in poor yield. ECU can also be prepared from ALC by aqueous hydrogen peroxide in the presence of titanium silicate (for example, TS-1) molecular sieves. The reaction is customarily a liquid-solid heterogeneous catalytic system, where an organic solvent like acetone, acetonitrile or mcthanol acts as a homogenizcr of aqueous and organic phases. A drawback of the method using solid TS-1 and dilute hydrogen peroxide is the use of environmentally dclrimentnl co-solvent such as neclone, iicetonilrile, methanol, tertiary butanol etc. Further, the separation of solvent after reaction is cumbersome, expensive and energy intensive. One more limitation of the prior art is the low yield of product due to side reactions like hydrolysis or solvolysis. The yield of ECH can be improved either by continuous removing water through azeotropic distillation or by using anhydrous hydrogen peroxide. Azeotropic distillation is cumbersome as well as expensive, and handling of anhydrous or nearly anhydrous solutions of hydrogen peroxide is prone to hazardous explosion. The main object of the present invention is to provide an improved process for preparation of ECH overcoming these drawbacks and to devise a solvent-free method. Another object of the present invention is to maximize the selectivity for ECU. In the method of present invention we solubilizc dilute aqueous hydrogen peroxide solution in organic medium i.e. ALC using microcmulsion technique, and carry out the oxidation. Since, this is a solvent free method, it improves the overall rate of the reaction as well as the percentage of ECH yield. The main feature of the present invention is the preparation of ECH by direct oxidation of ALC. The aqueous hydrogen peroxide, an oxidizing agent, is solubilized into ALC using suitable surfactant as emulsifier under mild stirring. The molar ratio of ALC : hydrogen peroxide in the reaction mixture may be taken in the range between 1:1 to 10:1. The concentration of AOT with respect to weight of the feed microemulsion may range from 0.5 to 10.0 wt %. Another feature of the present invention is that there is no need of using any organic co-solvent. This is a significant improvement over the prior art methods for the production of ECU in increasing the overall yield of ECH and in separation of the product from the mixture. Microemulsions (\vatcr-in-oil (w/o), or oil-in-watcr (o/vv)) are low viscous, compartmentalized but macroscopically homogeneous and thermodynamically stable phases in presence of surface active agent. The present invention makes use of a reverse microcmulsilication process for the solubili/ation of the hydrogen peroxide in continuous ALC by lowering the intcrfacial constraints. The purpose of avoiding the constraints can be achieved by using a suitable surfactant, for example sodium bis(2-ethylhexyl)sulfosuccinate, hereinafter referred to as AOT, Igcpal CO-720, Igepal CO-520, Igepal CO-990, didodecyldimethylamminoum bromide, dihexadecyldimethylammonium bromide etc. The surfactant is first dissolved In the ALC such that concentration of the solution is well above the Critical Micelle concentration (CMC). The concentration may range from 0.5 to 10 wt%. Accordingly, the present invention provides an improved process for the production of epichlorohydrin (ECH) which comprises reacting a mixture comprising allylchloride, aqueous hydrogen peroxide in the range of 10 to 70% and a surfactant as defined herein, with a solid titanium silicate zeolite catalyst, at a temperature ranging between 10-60° C , collecting the product after the reaction , demulsifying it by adding aqueous saturated salt solution, phase separating the product along with unconverted reactant, if any, and purifying the product(s) present in the organic layer by using conventional method as herein described, the said process characterized in using the said titanium silicate zeolite catalyst and aqueous hydrogen peroxide. The major advantage of the present invention lies in its offering very high levels of conversion and selectivity. In an embodiment of the present invention the concentration of the H2O2 solution may be in the range of 10 to 70%. However the preferred range of the H2O2 is 25-50%. In another embodiment, the surfactant may be selected from cationic, nonionic or anionic surfactants exemplified by and commercially known as OT, Igepal CO-720, Igepal CO-520, Igepal CO-990, didodecyldimethyl ammonoum bromide, dihexadecyldimethylammonium bromide titanium. In yet another embodiment of the present invention the catalyst used is Titanium silicate zeolite catalyst prepared as per the process described in Indian Patent No. 1,75,810. In yet another embodiment of the present invention the salt used for de-emulsifying may be selected from NaCl, KC1, A1C13- KBr, NaBr etc. In a feature of the invention the process could be worked in liquid phase either in batch, continuous stirred tank (CST) or conlinueous fixed bed reactor system or their combination thereof. In another feature of present invention the surfactant obtained as a solid residue can be reused. Hence, we have developed a novel catalytic method for the oxidation of the ALC, where environmentally detrimental use of co-solvent can be avoided by using a small percentage of surfactant for making microemulsion. Additionally, the microenuilsion system helps in achieving higher selectivity for epoxide formation. The process of the present invention is described by following examples which are illustrative only and should not be construdc to limit the scope of the invention in any manner Example 1 This example illustrates the procedure for epoxidation of ALC to ECH. The reaction was carried out in a tubular down flow fixed bed reactor. 6.8g catalyst (titanium silicate), was packed in the reactor and a microemulsion of hydrogen peroxide (47 wt.% aqueous solution) in ALC (molar ratio of hydrogen peroxide to ALC = 1:3, AOT = 3.8 wt. %) was passed over the catalyst bed at room temperature (ca. 27°C) and at weight hourly space velocity (W11SV) about 2.1. The reaction product was collected at an interval of Ih and demulsifed by adding aqueous saturated solution of sodium chloride. Separated organic phase was analyzed by gas chromatography. The results are recorded in Table 1. Table I. Epoxidation of ally 1 chloride with hydrogen peroxide over fixed catalyst (TS-1) bed. (Table Removed) Example 2 This example describes the effect of surfactant concentration on the conversion of ALC to ECU. Mixture of ALC, surfactant and 35 wt.% aqueous solution hydrogen peroxide (molar ratio ALC: H202 = 3:1) was passed through the catalyst bed (TS-1) at room temperature for 4h. The product mixture was collected and de-emulsified with saturated solution of sodium chloride. The organic layer was separated and analyzed by conventional gas-chromatographymcthod. The results arc presented in Table 2. Table 2 Effect of AOT Concentrations on the conversion of ALC in the cpoxidation with hydrogen peroxide over fixed catalyst (TS-1) bed. (Table Removed) Example 3: This example illustrates the effect of the reactant molar ratio on the conversion of the ALC to ECH. Microemulsions of ALC and hydrogen peroxide (50 wt.% aqueous solution) of different molar ratio were passed through a tubular reactor over catalyst TS-1 at room temperature. The product mixture was collected with an interval of one hour, de-emulsifying by saturated NaCl solution or by adding solid sodium chloride while shaking. The organic layer was separated and analyzed by conventional gas-chromatography method. The results are recorded in Table 3. Table 3 Effect of the different ALC : H->07 molar ratio on the conversion of allylchloride, time on stream = 3h. (Table Removed) Example 4: This example describes the effect of (he flow rate on (he conversion of (he ALC to ECH. Microemulsions of ally! chloride and 50 \v(.% aqueous solution of hydrogen peroxide (molar ratio = 3:1) and AOT 3.8% was passed through the catalyst bed (TS-1) with different WIISV at room temperature. The product mixture was collected after three hour and demulsiied with saturated solution of sodium chloride. The organic layer was separated and analyzed by conventional gas-chromatography method. The results are presented in Table 4. Table 4 Effect of WHSV (flow rate) on conversion of the allyl chloride to epichlorohydrin over catalyst bed (TS-1). (Table Removed) Example 5 This example illustrates the process in a batch reactor. In a typical experiment 7.65 g ALC, 2.52 g n2O2 (35 vvt. % aqueous solution) and 0.65 g AOT were contacted with 0.8 g catalyst under stirring at 30°C. The product sample was taken out and analyzed as mentioned in examples 1-4. The results as shown in Table 5 below Table 5 Epoxidation of allyl chloride to epichlorohydrin in a batch reaction over TS-catalyst: (Table Removed) Example 6 This example illustrates the effect of reaction temperature on ALC conversion and selectivity. In a lypic.il experiment 7.65 g ALC, 2.52 g II2O2 (45 wt. % aqueous solution) and 0.53 g AOT were contacted with 0.8 g catalyst under stirring at different reaction temperature for 3 h in each experiment. The product sample was taken out and analyzed as mentioned in examples 1-4. The results arc given in Table 6 below. Table 6 (Table Removed) Advantage The major advantage of the present invention lies in its offering very high levels of conversion and selectivity to desired product with case of separation. We claim: 1. An improved process for the production of epichlorohydrin (ECH) which comprises reacting a mixture comprising allylchloride, aqueous hydrogen peroxide in the range of 10 to 70% and a surfactant as defined herein, with a solid titanium silicate zeolite catalyst at a temperature ranging between 10-60° C , collecting the product after the reaction, demulsifying it by adding aqueous saturated salt solution, phase separating the product along with unconverted reactant, if any, and purifying the product(s) present in the organic layer by using conventional method as herein described , the said process characterized in using the said titanium silicate zeolite catalyst and aqueous hydrogen peroxide. 2. A process as claimed in claim 1 wherein the surfactant used is selected from cationic, non-ionic or anionic surfactants such as sodium bis (2 - ethylhexyl) sulfosuccinate, didodecyldimethyl ammonium bromide. 3. A process claimed in claims 1 to 3 wherein the salt used for demulsifying is selected from NaCl, KC1, A1C13, KBr, NaBr, etc. 4. A process for the production of eiphlorohydrin substantially as described herein with reference to the examples contained therein.

Documents:

2875-del-1998-abstract.pdf

2875-del-1998-claims cancelled.pdf

2875-del-1998-claims.pdf

2875-del-1998-complete specification (granted).pdf

2875-del-1998-correspondence-others.pdf

2875-del-1998-correspondence-po.pdf

2875-del-1998-description (complete).pdf

2875-del-1998-form-1.pdf

2875-del-1998-form-2.pdf

2875-del-1998-form-3.pdf

2875-del-1998-form-4.pdf

2875-del-1998-form-9.pdf