GB2086898A

GB2086898A - Process for The Chlorination of Residual Gases Containing Unsaturated Hydrocarbons

Info

Publication number: GB2086898A
Application number: GB8133279A
Authority: GB
Original assignee: Produits Chimiques Ugine Kuhlmann; Ugine Kuhlmann SA
Current assignee: Produits Chimiques Ugine Kuhlmann; Ugine Kuhlmann SA
Priority date: 1980-11-04
Filing date: 1981-11-04
Publication date: 1982-05-19
Also published as: EP0051524A1; KR830007473A; IL63941A; DK172880B1; IT8168270A0; AT379374B; ATA460981A; GB2086898B; FR2493307A1; JPS57106628A; IT1210613B; BR8107121A; DK485181A; BE890813A; IL63941A0; AR227206A1; SE442194B; KR850001546B1; SE8106500L; DE3167745D1

Description

1

SPECIFICATION Process for the Chlorination of Residual Gases Containing Unsaturated Hydrocarbons

The invention relates to a process for treating residual gases containing unsaturated hydrocarbon products and particularly residual gases obtained from the production of dichloroethane by oxychlorination of ethylene.

Industrial processes for the production of dichloroethane by reacting oxygen with a mixture 75 of hydrochloric acid and ethylene never give a total reaction and the gases leaving the oxychlorination reactor always contain unconverted ethylene. The unconverted ethylene is present in a not inconsiderable amount and 80 many processes have been developed with a view to reducing the loss of ethylene, generally by converting the residual ethylene into dichloroethane by complementary chlorination.

In French Patent 1 421 903, the gas released 85 on oxychlorination, after cooling to condense the dichloroethane formed, is treated in the vapour phase with chlorine on an iron-based catalyst.

This treatment is carried out at elevated temperature-from 80 to 250OC-which is a drawback since gaseous mixtures containing moist chlorine are highly corrosive, thus requiring either the use of expensive equipment or an increase in the maintenance costs. Moreover, the gaseous flux has to be heated to a high enough temperature to enable the reaction to proceed fairly rapidly, thus involving a high energy consumption.

To avoid these disadvantages, it has been proposed to effect the chlorination in the liquid phase in an unreactive solvent. Thus, British Patent 1 364 610 describes a process wherein, after drying, the residual gases from oxychlorination are passed into a reactor through which a current of inert liquid flows, preferably 1,2-dichloroethane, at the same time as chlorine is introduced in a sufficient quantity to convert a major part of the residual ethylene. The chlorination reaction takes place at from 35 to 850C in the presence of ferric chloride. However, owing to the high degree of dilution of the ethylene in the gas stream to be treated, this technique necessitates contacting with a very high flow rate of dichloroethane, thus requiring very large reactors which in turn lead to a costly investment in terms of the expected production of dichloroethane.

An aim of the present invention isto overcome 115 these disadvantages, Accordingly, the present invention provides a process for the chlorination of residual gases containing ethylene and/or another unsaturated hydrocarbon, wherein the residual gas is chlorinated, in the vapour phase, with chlorine in the presence of a catalyst.

The present invention makes it possible to convert the ethylene contained in residual gases from oxychlorination into 1,2-dichloroethane in an excellent yield; the reaction takes place at a GB 2 086 898 A 1 fairly low temperature which keeps low the energy costs incurred by the heating of gases, and also eliminates the risks of corrosion, without requiring the circulation of very much solvent. For this purpose, chlorine is added to the residual gas containing ethylene, preferably in a molar ratio C12/C21-14 of from 0.5 to 1.5, more preferably from 0.8 to 1.1. The mixture thus obtained is passed over a catalyst for a contact time of from 0. 1 to 10 seconds, preferably from 0.2 to 5 seconds (the contact time being defined as the ratio between the volume of catalyst (mi) and the flow rate by volume (mils)). The reaction temperature is usually from 0 to 1 501C, preferably from 15 to 800C. The catalyst may be, for example, active charcoal or alumina in pellet form.

The level of conversion of the ethylene is from 90 to 100%, whilst the yield of dichloroethane is virtually quantitative.

The invention is further illustrated by the following Examples.

The Examples were performed using residual gases from the oxychlorination of ethylene, but any inert residual gas containing ethylene or another unsaturated hydrocarbon may be treated in the same way, thus permitting easier recovery of a product of higher molecular weight.

Example 1

191 1/h of a gasous effluent from the oxychlorination of ethylene, having the following composition: C02 CO C2H4 100 HCI CH2CI-CH2C1 02 N2 2.1% 1.2% 1.2% 0.1% 0.03% 6.0% 89.37 are treated with 2.23 I/h of chlorine in the vapour phase (i.e. a molar ratio C12/C2 H4 of 0.973) at a temperature of 701C over 175 ml of active charcoal (Acticarbone AC40 made by Messrs CECA S.A. ). The contact time is therefore 2.6 seconds.

Under these conditions, the ethylene conversion rate is 97.5%.

Example 2

600 Vh of the gaseous effluent of Example 1 are treated with 6.9 1/h of chlorine (molar ratio C'2/C2H40.958), at a temperature of 700C. over 88 mi of active carbon, representing a contact time of 0.4 seconds.

The ethylene conversion rate is 96%.

Example 3

600 Vh of the gaseous effluent of Example 1 are treated with 7.9 1/h of chlorine (molar ratio C12/C21-14=1.097) under the same conditions as in Example 2, i.e. at a temperature of 700C over 88 mi of active charcoal (contact time: 0.4 seconds).

2 GB 2 086 898 A 2 The ethylene conversion level is 96%, as in Example 2. However, excess chlorine which has not reacted, namely, 1.02 Vh, is present in the gas after the reaction, but can easily be eliminated by 5 conventional methods.

Example 4

1/h of a gaseous effluent from the oxychlorination of ethylene, having the following 60 composition:

C02 CID C2H4 CF12-CI-CH2C1 02 15 N2 2.5% 1.0% 1.27% 0.12% 6.0% 89.11% are treated with 2.35 Vh of chlorine (molar ratio C'2/C2H4==0.984) at a temperature of 200C over mi of active charcoal. The contact time is 3.5 70 seconds.

Under these conditions, the ethylene conversion level is 97.5%.

Example 5

216 Vh of a gaseous effluent having the 75 following composition:

C02 CID C2H4 02 N2 1.9% 0.8% 0.7% 6.0% 90.6% are treated with 1.38 1/h of chlorine in the vapour phase, at a temperature of 5011C, over 175 m] of 85 active charcoal, i.e. with a contact time of 2.9 seconds.

Under these conditions, where the molar ratio of chlorine to ethylene is on] y 0.913, the ethylene conversion level is 89%.

Example 6

168 I/h of the gaseous effluent in Example 5 are treated with 1.18 I/h of chlorine (molar ratio C'2/C2H4=1.003) at a temperature of 90'C over ml of alumina in pellet form, the contact time being 2.8 seconds.

The ethylene conversion level is 97.2%.

Example 7

189 I/h of the gaseous effluent of Example 5 are treated with 1.8 I/h of chlorine (molar ratio C'2/C2H4=1.360) at a temperature of 501)C over ml of alumina in pelletform, i.e. a contact time of 2.5 seconds.

The ethylene conversion level is 100%. After 105 the reaction, unreacted excess chlorine, i.e. 0.5 1/h, is found in the gas.

Example 8 1. 140]/h of a gaseous effluent from the oxychlorination of ethylene having the following composition:

C02 C0 C2H4 CH2CI-CH2C1 02 N2 1.6% 0.7% 0.59% 0.11% 6% 91% is treated with 12.6 I/h of chlorine (molar ratio C12, IC2H4=1.873) at a temperature of 900C over 17-5 ml of alumina. The contact time is thus 0.4 seconds.

The ethylene conversion level is 96.6%. Excess unreacted chlorine, i.e. 6.1 Vh, is found in the gas after the reaction.

Claims

Claims 1. Process for the chlorination of residual gases containing

ethylene and/or another unsaturated hydrocarbon, wherein the residual gas is chlorinated, in the vapour phase, with chlorine in the presence of a catalyst.
2. Process according to Claim 1, wherein the catalyst is active charcoal.
3. Process according to Claim 1, wherein the catalyst is alumina. 80
4. Process according to any one of Claims 1 to 3, wherein the molar ratio of chlorine to unsaturated hydrocarbon is from 0.
5 to 1.5. 5. Process according to Claim 4, wherein the molar ratio is chlorine to unsaturated hydrocarbon is from 0.8 to 1. 1.
6. Process according to any one of Claims 1 to 5, wherein the reaction temperature is from 0 to 1500C.
7. Process according to Claim 6, wherein the reaction temperature is from 15 to 80"C.
8. Process according to any one of Claims 1 to 7, wherein the contact time with the catalyst is from 0. 1 to 10 seconds.
9. Process according to Claim 8, wherein the contact time with the catalyst is from 0.2 to 5 seconds.
10. Proc ess according to any one of Claims 1 to 9, wherein the residual gases are those resulting from the production of dichloroethane by oxychlorination of ethylene and wherein the chlorinated product obtained is dichloroethane.
11. Process according to Claim 1 substantially as described in any one of the foregoing Examples.
12. A chlorinated hydrocarbon whenever obtained by a process as claimed in any one of the preceding claims.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1982. Published by the Patent Office. 25 Southampton Buildings. London, WC2A 1 AY, from which copies may be obtained.