PROCESS FOR THE PREPARATION OF PURE ALKYL TERT.-ALKYL ETHERS AND HYDROCARBON RAFFINATES WHICH ARE LARGELY FREE FROM ISOOLEFINS AND FROM ALKANOLS

摘要

Hydrocarbon mixtures which contain at least one tertiary olefin are reacted with an alkanol on an acid cation exchanger, a product mixture being formed which contains the resulting alkyl tertiary-alkyl ether,excess unreacted alkanol,and the residual hydrocarbons which were contained in the original hydrocarbon mixture. Furthermore, this product mixture contains minor amounts of unreacted tertiary-olefin, it being possible for the contents to be reduced to 0 at complete conversion. The excess, unreacted alkanol is removed from the resulting product mixture, or from its part streams produced in the working-up, by absorption on a synthetic ion exchanger containing groups which exchange cations or anions, or mixtures of such ion exchangers in the form of an absorber resin. The alkanol to be fed into the reaction zone is at least partially taken by desorption from an absorber resin charged with alkanol, the process being carried out with the aid of the hydrocarbon mixture containing at least one tertiary olefin. For alkanol absorption and alkanol desorption, at least two absorber resin layers are employed and are switched from absorption to desorption and vice versa, in cyclic operation. The product mixture leaving the etherification reactor can firstly be freed on an absorber resin from excess alkanol, and can thereafter be separated into the alkyl tertiary alkyl ether and the residual gas by distillation. However, the product mixture leaving the etherification reactor can also firstly be separated into the alkyl tertiary-alkyl ether and the residual gas by means of distillation, at least one of the part streams obtained containing alkanol, and thereafter the alkanol-containing part stream or streams can be separated from the alkanol, on an absorber resin.