GB2095244A - Chlorination of alkyl chlorides - Google Patents

Abstract

A process for the selective production of chloroalkanes comprises contacting an alkyl chloride and chlorine in the vapour phase at an elevated temperature in the presence of a catalyst comprising a zeolite. Useful for the production of methylene chloride from methyl chloride.

Description

SPECIFICATION Production of chloroalkanes The present invention relates to a process for the selective production of chloroalkanes by the chlorination of alkyl chlorides.

Chloroallcanes are prepared industrially by the gas phase direct chlorination of the corresponding alkane and/or alkyl chloride. Fbr example, methane may be chlorinated in the gaseous phase to give a mixture of chloromethanes, viz. methyl chloride, methylene chloride chloroform, and carbon tetrachloride. Alternatively, methyl chloride, preferably obtained by the direct hydrochlorination of methanol in either the gaseous or liquid phase, may be chlorinated in the gaseous phase to give the three heavier chloromethanes, and if desired, the hydrogen chloride produced in the chlorination reaction may be recycled for reaction with methanol.The aforesaid chlorination processes for the production of chloromethanes are described, for example, in the following general references: "Chloromethanes" E M Forrest Encyclopedia of Chemical Processing and Design, Volume 8 pages 214-270, 1 979 and in "Chloromethanes" Kirk-Othmer Encyclopedia of Chemical Technology 3rd Edition, Volume 3 pages 677-714, 1 979.

The demand for specific chloroalkanes varies from time to time and it is desirable to have a process which is capable of achieving a high control of product selectivity in respect of the chloroalkanes obtained from a given alkyl chloride. We have now found a catalytic process which is particularly effective for the selective production of methylene chloride from methyl chloride.

According to the present invention we provide a process for the selective production of chloroalkanes which comprises contacting an alkyl chloride and chlorine in the vapour phase at an elevated temperature in the presence of a catalyst comprising a zeolite.

A wide range of zeolites may be employed as catalysts, providing they are stable under chlorination conditions. Suitable zeolites include X-type zeolites (e.g. as described in UK Patent 1450411: US Patent 2882244), Y-type zeolites (e.g. as described in US Patent 3130007), and zeolite Nu-2 (as described in our copending UK Application No 8040782).

The zeolite catalysts are preferably partially or wholly exchanged with metal cations, for example one or more of copper, silver, magnesium, zinc, manganese, cobalt, nickel and ianthanide cations. The preferred catalysts comprise zeolites which are partially or wholly exchanged with silver and/or manganese cations, more preferably silver and manganese cations.

It will be appreciated that during chlorination, the aforesaid metal cations, which may be present as metals or metal compounds e.g. oxides, may be partially or wholly converted under the reaction conditions to chlorides during the course of the reaction.

The catalyst may be employed in fixed, moving or fluidised beds of the appropriate size.

The process of the invention is applicable to a range of alkyl chloride starting materials, for example alkyl chlorides having 1 to 4 carbon atoms. The process is particularly applicable to the selective production of methylene dichloride from methyl chloride.

The reaction temperature may vary according to the alkyl halide reactant employed. Suitably, for example, for the chlorination of methyl chloride or ethyi chloride, the temperature is in the range 275-5000C and preferably between 300 and 5000C, for example 3500C to 4500C.

450"C.

The reaction is normally carried out under atmospheric or superatmospheric pressure, e.g. at a pressure in the range 1 to 100 bars.

The process is preferably carried out in the presence of a source of molecular oxygen, e.g. oxygen itself or oxygen enriched air, since this minimises coking problems, aids zeolite stability and is essential for HCI utilisation via the Deacon reaction. The presence of oxygen is also effective in improving the ratio of methylene chloride to chloroform and carbon tetrachloride for a given level of conversion. UsefL chlorination will however take place in the absence of oxygen. An inert diluent such as nitrogen may also be present.

The molar ratios of alkyl chloride to chlorine are suitably in the range 10 to 1 to 1 to 10, for example 2 to 1.

The molar ratios of alkyl chloride to oxygen (when present) are suitably in the range 100 to 1 to 1 to 1, for example 2 to 1.

The products of the reaction may be isolated and used as such or, if desired, may be recycled wholly or partially to the chlorination reaction in order to increase the yield of specific chloroalkanes.

The invention is illustrated by the following Examples.

EXAMPLE 1 A Y type zeolite of formula Na2O.AI2O < .5.1 siO2 was saturated with 10 ml of 50% MnNO3)2.6 H20 solution for 1 6 hours and then filtered and washed thoroughly with water. The white solid was then treated with 10 ml of 80% AgN03 solution for 1 6 hours, filtered washed, dried at 1 200C for 1 6 hours and then calcined at 4500C, The resulting catalyst was shown by analysis to contain 18.9% silver and 2.4% manganese. After grinding to 20-30 mesh size the catalyst was packed as a 10 cm bed in a 6.3 mm OD microreactor tube surrounded by a resistively heated furnace and connected to an on-line GLC system.After treatment in flowing chlorine at 4000 C, the catalyst was tested with methyichloride over a range of gas feed compositions and temperatures. The results are shown in Table 1.

A comparative example was carried out at 4000C in which the silver/manganese/zeolite catalyst was replaced by an equal quantity of pumice ground to the same mesh size. The results are shown in Table 2. A comparison of these results with those shown in Table 1 illustrates the greater selectivity to methylene dichloride when using the silver/manganese/zeolite catalysts.

EXAMPLE 2 The Y type zeolite of Example 1 was also tested without cation exchange and found to have beneficial performance with respect to using pumice alone. The results are given in Table 3.

TABLE 1

Reaction Selectivity % Selectivity % temp. Gas feed (ml/min) Conversion ( C) CH3Cl Air Cl2 (CH3Cl mol %) CH2Cl2 CHCl3 CCl4 CO2 350 4 10 2 17.1 94.4 1.4 - 4.2 375 4 10 2 31.3 92.0 4.8 ~ 3.0 400 4 10 2 39.8 90.4 7.3 0.9 1.5 350 4 10 1 10.9 94.8 0.2 ~ 4.9 375 4 10 1 12.0 94.9 0.7 ~ -4.4 400 4 10 1 19.1 97.5 ~ ~ 2.5 400 4 10 1.5 27.6 96.8 1.1 ~ 2.0 TABLE 2

Reaction Gas feed (ml/min) Selectivity % temp. Conversion ( C) CH3Cl Air Cl2 (CH3Cl2) CHCl3 CCl4 CO2 300 4 10 4 2.2 96.1 2.2 - 1.6 325 4 10 4 9.5 93.7 5.8 ~ 0.5 350 4 10 4 23.5 90.9 8.8 0.2 0.2 375 4 10 4 51.7 79.9 19.3 0.6 0.2 400 4 10 4 67.7 68.4 29.3 2.1 0.1 400 4 10 1.5 28.3 87.8 11.3 0.4 0.5 400 4 10 8 91.4 39.0 51.4 9.6 0.07 TABLE 3

Gas feed (ml/min) Selectivity % Temperature Conversion C Air CH3Cl Cl2 (CH3Cl mol %) CO2 CH2Cl2 CHCl3 CCl4 400 10 4 1.5 26.1 0.2 98.5 1.4 400 10 4 2 32.7 0.1 97.7 2.0 0.1 400 10 4 2.5 34.0 0.1 97.4 2.5 400 10 4 4 47.5 0.1 95.3 4.6 0.1 400 10 4 8 62.9 0.1 88.2 11.2 0.3 375 4 4 36.0 0.1 98.6 3.1 0.2 350 10 4 4 19.3 0.2 98.1 1.6 325 10 4 4 7.2 0.2 99.1 0.7 300 10 4 4 2.0 - 100 - EXAMPLE 3 A catalyst containing silver, manganese and magnesium was prepared as in Example 1-, exchanging a Y type zeolite with an aqueous solution of the 8.4 ml of 50% manganous nitrate solution, 2.69 of magnesium nitrate in 5 ml of water and 1.7 g of silver nitrate in 5 ml water After calcination and pretreatment with chlorine the catalyst was tested under various conditions of feed gas and temperature. The results are shown in Table 4.

The results obtained in presence of nitrogen diluent rather than air are presented -in Table 5 together with those for the blank (pumice) reaction under similar conditions.

EXAMPLE 4 A catalyst was prepared as in Example 2 but substituting yttrium for magnesium. 3.4 g of the zeolite was thus exchanged with a solution containing 3 g yttrium nitrate and 1t.33 g of silver nitrate in 10 ml of water and 6.6 ml of a 50% solution of manganous nitrate.

The results obtained with a 10 cm bed length and flow rates of 4 ml/min of methylchloride and chlorine and 10 ml/min of air are shown in Table 6.

EXAMPLE 5 A catalyst was prepared as in Example 1 but tested in a 1 metre bed length reactor and the behaviour compared with the same bed length of pumice. Reaction temperaturewas 2800C, feed composition was 20% (vol) of methylchloride and nitrogen was the only diluent. Chlorine concentration was varied in order to vary the level of conversion per pass. The reduced proportions of CHCI3 and CCI4 produced in the exit stream from the catalyst with respect to that from pumice are illustrated in Table 7 TABLE 4

Reaction Gas feed (ml/min) Selectivity % temp. Conversion ( C) Air CH3Cl Cl2 (CH3Cl mol %) CO2 CH2Cl2 CHCl2 CCl4 400 10 4 1 3.6 8.2 91.8 - 400 10 4 2 17.4 0.9 97.7 ~ 1.4 400 10 4 3 35.5 0.3 99.0 ~ 0.7 400 10 4 3.8 40.0 0.3 99.1 0.1 0.5 400 10 -4 4 42.8 0.3 98.3 0.9 0.5 375 10 4 -4 34.5 0.6 99.0 0.2 0.2 350 10 4 4 31.9 0.9 97.9 1.2 | ~ 325 10 4 4 | 19.9 | 1.3 97.6 | 1.1 1 TABLE 5

Gas Feed (ml/min) Selectivity% Temperature Conversion Substrate ( C) N2CH2Cl Cl2 mol % CH2Cl2 CHCl3 CCl4 Catalyst 300 10 4 1 19.0 98.0 2.0 -# Pumice 300 10 4 1 6.6 94.7 5.3 Catalyst 325 10 4 2 23.2 94.7 5.3 Pumice j 325 10 4 2 # 24 90.2 l 9.7 # 0.1 TABLE 6

j Selectivity % Conversion Temperature C | (CH3Cl mol %) | CO2 | CHCl3 | CCl4 300 32.3 2.5 97.3 ~ 0.2 325 40.1 1.2 97.9 | 0.9 | ~ 350 40.3 0.7 99.2 0.1 375 39.0 0.3 99.7- - 400 38.3 0.2 99.7 - 0.1 TABLE 7 Chloroform Production

Pumice Catalyst CH3Cl Conversion % | CHCl3 Selectivity % | CH3Cl Conversion | CHCl3 Selectivity % 21 5.0 24 2.4 35 10.0 35.5 4.1 43 13.9 45.5 6.8 62 19.3 59 8.3 -CC14 Production

Pumice Catalyst CHl Conversion % I CCl4 Selectivity'% CH3CI Conversion % CCl4 Selectivity % 31.5 0.5 33 0.12 36 0.55 38 0.15 55.5 1.08 57.5 0.56 77 2.1 74 | 1.36

Claims (9)

1. A process for the selective production of chloroalkanes which comprises contacting an alkyl chloride and chlorine in the vapour phase at an elevated temperature in the presence of a catalyst comprising a zeolite.

2. A process according to claim 1 wherein methyl chloride is reacted with chlorine to form methylene chloride.

3. A process according to claim 1 or claim 2 wherein the catalyst comprises a zeolite that has been partially or wholly exchanged with one or more of copper, silver, magnesium, zinc, manganese, cobalt, nickel and lanthanide cations.

4. A process according to claim 3 wherein the catalyst comprises a zeolite that has been partially or wholly exchanged with silver and/or manganese cations.

5. A process according to any one of the preceding claims wherein the reaction temperature is in the range 300 to 5000C.

6. A process according to any one of the preceding claims wherein the reaction is carried out in the presence of a source of molecular oxygen.

7. A process according to claim 6 wherein the molar ratio of alkyl chloride to oxygen is in the range 100:1 to 1:1.

8. A process according to any one of the preceding claims wherein the molar ratio of alkyl chloride to chlorine is in the range 10:1 to 1:10.

9. A process according to claim 1 substantially as hereinbefore described with reference to the foregoing Examples.