GB2095243A - Production of methylene chloride - Google Patents

Abstract

A process for the selective production of methylene chloride comprises contacting methane and chlorine in the vapour phase at a temperature above 275 DEG C in the presence of a catalyst comprising a zeolite.

Description

SPECIFICATION Production of methylene chloride The present invention relates to a process for the selective production of methylene chloride by the chlorination of methane.

Chloroalkanes are prepared industrially by the gas phase direct chlorination of the corresponding alkane and/or alkyl chloride. For 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 clorination 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, 1979 and in "Chloromethanes" Kirt-Othmer Encyclopedia of Chemical Technology 3rd Edition, Volume 5, pages 677-714, 1979.

British Patent 1,1 72,002 describes a process for the chlorionation of hydrocarbons which comprises contacting a mixture of hydrocarbon and chlorine with a zeolite catalyst at a temperature of 500C to 2500C temperatures of from 650C to 1 500C being most preferred. Although this patent envisages the use of a wide variety of both hydrocarbon starting materials and zeolites (including metal exchanged zeolites), the only exemplification relates to the chlorination of ethane and of propane. Each of the aforesaid alkane starting materials give rise to a wide spectrum of chlorinated products (including about 48% of unknown product from propane and 67% unknown product from ethane) and there is no marked selectivity to any particular chlorinated product.

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 alkane. We have now found a catalytic process which is particularly effective for the selective production of methylene chloride from methane as measured by the methylene chloride/chloroform ratio at any given level of conversion.

According to the present invention we provide a process for the selective production of methylene chloride which comprises contacting methane and chlorine in the vapour phase at a temperature above 2750C 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 and oxychlorination conditions. Suitable zeolites include X-type zeolites (e.g. as described in UK Patent 1,450,411; US US Patent 2,882,244), Y-type zeolites (e.g. as described in US Patent 3,130,007), and zeolite Nu-2 (as described in our copending UK Application No 80 40782).

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 lanthanide ions. 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 catalysts may be employed in fixed, moving orfluidised beds of the appropriate size.

The reaction temperature is suitably in the range 275-5000C, and preferably between 300 and 500cm, for example 3500C to 4500 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. Useful chlorination will however, take place in the absence of oxygen. An inert diluent such as nitrogen may also be present.

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

The molar ratios of methane to oxygen (when present) are suitably in the range 10 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 methylene chloride.

The invention is illustrated by the following Examples: Example 1 A Y type zeolite of formula Na2O.Al203.5.1 SiO2 was saturated with 1 Oml of 50% Mn(NO3)2.6H20 solution for 16 hours and then filtered and washed thoroughly with water. The white solid was then treated with 1 Oml of 80% AgNO3 solution for 1 6 hourrs, filtered, washed, dried at 1 200C for 16 hours and then calcined at 4500C for 1 6 hours. The resulting catalyst was shown by analysis to contain 2.8% silver and 0.4% manganese. After grinding to 20-30 mesh size the catalyst was packed as a 1 Ocm bed in a 6.3 mm O.D. microreactor tube surrounded by a resistively heated furnace and connected to an online GLC system.After treatment in flowing chlorine at 4000 C, the catalyst was tested 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 (as compared with chloroform) when using the silver/manganese/zeolite catalyst.

Example 2 A catalyst was prepared in Example 1 containing copper, silver and manganese by exchanging a Y type zeolite (Na2O, Al2O3. 5.1 SiO2) with a solution of copper, silver and manganese nitrates to give a final metals concentration of X.

TABLE 1

Gas feed (ml/min) Selectivity % Reaction Methane Temp. CH4 : C 12 : Air Conversion CH3C I CH2C 12 CHC 13 002 3500 4 : 2 : 10 10.7 84.3 6.8 - 8.9 350"C 4 : 4 : 10 19.1 76.2 13.9 0.4 9.4 400 C 4 : 2 : 10 27.2 76.9 21.1 0.4 1.7 400-C 4 : 4 : 10 34.7 71.3 0.3 25.0 0.3 1 3.4 TABLE 2

Gas feed (ml/mi;l) Conversion Selectivity % Methane/CI,/Air (CH, mol O/.) CHFI CH,CI, CHC 13 CC14 CO? 5 /1/ 5 79.4 16.7 2.1 5 / 3/ 5 28.2 63.7 27 9 1 73 5 / 3/ 5 28.2 63.7 27.9 7.3 ~ 1.1 5 / 5i 5 40.1 49.9 43.7 14.7 - 0.7 5 /10/ 5 62.0 29.1 33.6 31.7 5.0 0.5 5 /20/ 5 75.7 18.5 28.8 40.7 11.5 0.4 5 / t/ 0 11.5 82.4 14.5 1.3 - 1.7 5 /3/ 0 22.9 65.6 26.9 5.8 - 0.9 5 /5/ 0 33.5 51.6 35.0 12.8 - 0.6 5 /10/ 0 59.8 26.8 35.6 31.6 5.5 0.4 The catalytic results obtained at 4000C are as shown in Table 3.

Example 3 A catalyst containing copper, potassium and lanthanum was prepared by saturating an Y type zeolite (Na2O, Awl203. 5.1 SiO2) with a solution containing 1 3.4g of CuCI2, 2.89 of LaCI3 7H20 and 3.7g of KCI for 16 hours. After filtering, washing and drying at 1200C, the resulting material was calcined at 4500C for 16 hours and tested as in Example 1 at 4000C in a gas stream of methane (4ml/min) chlorine (4m1/min) and air ( 1 Oml/min). The results are shown in Table 4.

Example 4 A catalyst containing 36% silver and 14% manganese was prepared as in Example 2 from 13 X molecular sieve material and was tested at 4000 C. The results are shown in Table 5.

Example 5 A catalyst containing silver, manganese and magnesium was prepared as in Example 1, exchanging Y type zeolite with an aqueous solution of the nitrates (8.4ml of 50% manganese nitrate solution 2.6g magnesium nitrate in 5ml of water and 1 .7g of silver nitrate in 5ml water). After calcination and pretreatment with clorine, the catalyst was tested at 4000 C. The results are shown in Table 6.

TABLE 3

Selectivity % Gas Feed (ml/min) Methane Methane/air/chlorine Conversion % CH3Cl CH2Cl2 CHCl3 CO2 4 /10/ 2 46.2 67.9 28.1 - 4 4 /10/ 2.25 49.1 62.9 33.5 0.33 3.3 4 /10/ 2.5 49.0 61.5 34.0 1,93 2.5 TABLE 4

Selectivity % Reaction temp. C Conversion CH4 -CH3CI I -CH2CI2 CHCl3 CO2 325 24.6 58.7 24.6 -0.9 15.9 350 28.0 60.6 27.4 1,4 10.6 375 37.4 55.4 32.6 1 4.4 t.6 400 41.7 52.1 33.5 8.2 6.2 TABLE 5

Gas feed (ml/min) Selectivity % Air Methane Chlorine % CH, Conversion CH,C I CHCI, CO, 10 4 1 14.9 78.7 9.2 1 I 12.0 1 10 4 2 28.7 63.9 24.2 0.5 11.5 10 4 2 28.7 63.9 24.2 0.5 11.5 10 4 4 40.6 52.6 32.7 1.2 13A 10 4 6 48.7 50.4 44.3 4.4 21.2 10 4 8 66.7 24.6 33.0 17.7 24.8 TABLE 6

Selectivity % Gas Feed (mllmin) Selectivity % Air CH4 012 % CH4 Conversion CH3CI CH2C12 CHOl3 CO2 10 4 3.0 48.0 68.4 28.9 0 2.2 10 5 3.5 47.0 66.0 31.0 0 -3.0 10 5 4.0 59.6 60.4 36.5 0 3.0 10 5 4.5 60.4 56.5 40.6 0.2 2.7 10 5 4.75 58.8 55.5 38.9 3.0 2.6 10 5 5.0 65.3 54.2 39.7 3.9 2.2

Claims (8)

1. A process for the selective production of methylene chloride with comprises contacting methane and chlorine in the vapour phase at a temperature above 2750C in the presence of a catalyst comprising a zeolite.

2. A process according to claim 1 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 ions.

3. A process according to claim 2 wherien the catalyst comprises a zeolite that has been partially or wholly exchanged with silver and/or manganese cations.

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

5. 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.

6. A process according to claim 5 wherein the molar ratio of methane to oxygen is in the range 10:1 to 1:1.

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

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