Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1995-08-15
1998-03-17
Ivy, C. Warren
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C07C 1715
Patent
active
057289050
DESCRIPTION:
BRIEF SUMMARY
This case is a 35 USC 371 National stage filing of PCT/G894/01944, published as WO95/07251 on Mar. 16, 1995.
The present invention relates to a process for the production of vinyl chloride monomer (VCM) from ethane via oxychlorination of ethane. More particularly, the invention relates to a method for controlling the selectivity of the oxychlorination of ethane.
VCM is most commonly produced from ethylene and chlorine feeds by chlorinating ethylene to produce 1,2-dichloroethane and subsequently dehydrochlorinating this intermediate to yield VCM.
The cost of ethylene is a significant contribution to the final cost of VCM produced by this method. Accordingly, interest has been shown in alternative hydrocarbon feeds in VCM production.
A prime candidate for an alternative hydrocarbon from which VCM may be produced is ethane. Not only is ethane cheaper than ethylene, but the chemistry of its conversion to VCM has distinct advantages. For example, the favoured oxychlorination reaction is a single step process in which ethane can be directly converted to VCM: products+H.sub.2 O chloride or a chlorinated hydrocarbon.
The selectivity of this reaction to VCM in favour of the "other products" is not total and is a source of inefficiency in the oxychlorination process. Other products may include recyclable intermediates such as ethylene and 1,2-dichloroethane, which may ultimately be converted to VCM. However, an appreciable percentage of these other products comprises burning products (mainly CO.sub.2) which result from oxidation of ethane in an uncontrolled manner.
Such products cannot be economically recycled in the VCM production process and represent wastage of raw material.
The selectivity of the oxychlorination reaction towards VCM and, most importantly, away from the burning products may be improved in a number of ways. A number of catalysts have been proposed in the art which affect the selectivity of the oxychlorination reaction. For example, GB 1492945 (BP) discloses the use of a Copper/Potassium/Cerium catalyst for the oxychlorination of ethane. However, the product spectrum quoted in the results is incomplete, with up to 18% of the ethane feed unaccounted for. Furthermore, the ethane feed is diluted with Nitrogen to an impractical degree.
In our copending United Kingdom Patent Application No. 9318501.5, filed contemporaneously herewith, we disclose a novel catalyst for catalysation of the oxychlorination reaction. A full spectrum of by-products is given in the examples of this application.
We have now developed a new and different technique for the reduction of the amount of burning products generated during the oxychlorination reaction. The technique may be used in any oxychlorination process, for example that described in our copending United Kingdom Patent Application No. 9318497.6, filed contemporaneously herewith, in conjunction with any catalyst.
According to a first aspect of the present invention, there is provided a method for the production of VCM by catalytic oxychlorination of ethane wherein HCl is supplied in excess of the stoichiometric requirement for chlorine in the reaction.
The HCl may be the only source of chlorine in the oxychlorination reaction. Alternatively, it may be supplied together with a second chlorine source, such as a chlorinated hydrocarbon or chlorine itself. All the chlorine requirement may be supplied by the second chlorine source.
In general, the greater the excess of HCl supplied over its stoichiometric requirement the greater the beneficial effect on the selectivity of the oxychlorination reaction. Where there is no requirement for HCl, because all the chlorine requirement is supplied in an alternative form, any quantity of HCl which is added will have a beneficial effect.
The ratio of HCl to ethane used in the reaction is preferably in the range 0.1 to 10 on a molar basis, and advantageously in the range 0.5 to 3.
Because not all the HCl is consumed in the reaction, HCl will leave the reactor together with the products of the reaction. Preferably, the excess HCl is r
REFERENCES:
patent: 3551506 (1970-12-01), Weinstein
patent: 3629354 (1971-12-01), Beard
patent: 4100211 (1978-07-01), Magistro
patent: 5097083 (1992-03-01), Stauffer
Clegg Ian Michael
Hardman Ray
EVC Technology AG
Ivy C. Warren
Smith Lyman H.
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