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Abstract

The present invention concerns a process for preparing tertiary alkyl ethers. The process comprises the steps of contacting in the presence of a catalyst a feedstock containing saturated hydrocarbons and dienes having 4 to 7 carbon atoms with an excess of hydrogen in relation to the amount of dienes in the feed in order selectively to hydrogenate at least a part of the dienes, feeding the treated hydrocarbon feedstock together with at least a part of the unreacted hydrogen to a catalytic distillation reactor system which includes at least one distillation column, reacting the C.sub.4-7 isoolefines of the feedstock with methanol or ethanol in the presence of a catalyst to form tertiary alkyl ethers, subjecting the reaction mixture to distillation in the distillation column, recovering the alkyl ethers and substantially all of the unreacted hydrocarbons with the bottoms product of the distillation, withdrawing an overhead product of the distillation, which mainly contains an azeotrope of saturated C.sub.4 hydrocarbons and the alkanol, and maintaining the pressure of the distillation column at least essentially constant by adjusting the amount of gaseous distillate containing hydrogen in the column. The selective hydrogenation operation of the present invention reduces the amount of dienes contained in the feed to below 0.5% and also causes isomerization of olefins to increase the amounts of reactive olefins.

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First Claim