Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1995-03-17
1997-04-08
Evans, Joseph E.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
502 38, 549536, 549537, C07D30110, C07D30304
Patent
active
056189540
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP93/03352 Nov. 30, 1993.
The present invention relates to a process for preparing 3,4-epoxy-1-butene by the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases over silver-containing catalysts and isolation of the 3,4-epoxy-1-butene from the reaction exit mixture.
3,4-Epoxy-1-butene, also known as butadiene monoxide and vinyl-oxirane, is an intermediate for preparing, for example, tetrahydrofuran, which can be prepared therefrom for example by the process of U.S. Pat. No. 5,034,545 by the isomerization of 2,5-dihydrofuran and its subsequent hydrogenation. It is also used for preparing 1,2-butylene oxide (cf. U.S. Pat. No. 5,117,013). Economical production of the aforementioned chemicals, which are needed in large amounts, on the basis of the starting material 3,4-epoxy-1-butene requires an efficient, economical process for preparing 3,4-epoxy-1-butene. Such a process has not been available to date.
For instance, WO 89/07101 describes a process for the gas phase epoxidation of 1,3-butadiene with oxygen or oxygen-containing gases over silver-containing catalysts. The yields and selectivities achieved are initially fairly good, but the silver-containing catalysts used very rapidly decline in activity, losing almost 90% of their original activity within 24 hours. So this process is unsuitable for preparing 3,4-epoxy-1-butene on an industrial scale.
Presumably this deactivation is due to the catalyst surface becoming coated with decomposition products of the vinyl-oxirane--a process which will hereinafter be referred to as coking. Also, the term "deactivation" as used hereinafter is to be understood as meaning, unless otherwise stated, the deactivation of the silver catalyst by coking processes during vinyl-oxirane production which leads to a rapid decrease in activity, i.e. to a more than 50% decrease in the initial activity of the silver-containing catalyst within a few hours or days. This type of deactivation is accordingly distinguished from the normal deactivation which the silver-containing catalyst undergoes in the course of months or years as a consequence of aging processes, such as thermal damage to the catalyst, sintering processes, phase separation or the gradual dragout of catalyst particles.
U.S. Pat. No. 5,117,012 concerns a process for working up the gaseous reaction exit mixture from the gas phase epoxidation of 1,3-butadiene by the process of WO 89/07101 wherein the hot, gaseous reaction exit mixture is quenched by means of liquid 1,3-butadiene. It is mentioned in the referenced document that the reactor feed of 1,3-butadiene, oxygen and inert gas should contain less than 5 mol %, based on the total feed, of water, since otherwise appreciable losses of 3,4-epoxy-1-butene are likely due to diol formation.
It is an object of the present invention to provide a process for the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases which makes it possible to prepare 3,4-epoxy-1-butene on an industrial scale in an economical manner, in particular with the activity of the catalysts used remaining at the initial level for a prolonged period.
We have found that this object is achieved by a process for preparing 3,4-epoxy-1-butene by the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases over silver-containing catalysts and isolation of the 3,4-epoxy-1-butene from the reaction exit mixture, which comprises performing the gas phase epoxidation in the presence of from 6 to 80 mol % of water vapor, based on the gas mixture supplied to the reactor.
We have also found a process for reactivating silver-containing catalysts which have been used for preparing 3,4-epoxy-1-butene by the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases and have become deactivated by coking, which comprises treating the deactivated silver-containing catalysts at from 100.degree. to 400.degree. C. with water vapor and oxygen or oxygen-containing gases.
The process of t
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Boeck Stefan
Fischer Martin
Fischer Rolf
Herzog Klaus
Vogel Herbert
BASF - Aktiengesellschaft
Evans Joseph E.
Shurtleff John H.
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