ALKYLATION PROCESS

摘要

INVENTION: IMPROVED ALKYLATION PROCESS INVENTORS: R. L. STURTEVANT, A. B. GANCY and B. I. KARSAY An improved process for the alkylation of isoparaffins by olefins in the presence of a sulfuric acid catalyst is disclosed. Improvement in the octane rating of the product alkylate is achieved by the periodic fortification of the sulfuric acid catalyst with sulfur trioxide-bearing fortifying agents and the incorporation of a holding time to delay the return of the fortified acid to the alkylation zone. Fortification is employed less than 6% of the time the catalyst is in contact with the hydrocarbons and a preferred water content of between 1.5% and 2.5% is maintained in the acid. By maintaining an optimum water content and fortifying less frequently, lower water and organic build-up rates are observed than previously thought possible. By incorporation of a holding time before the acid is returned to the alkylation reactor, there is essentially complete utilization of the fortifying agent for water removal and no free SO3 is available for harmful side reactions with the hydrocarbon feeds in the reactor. When the organic impurities dispersed in the recycle acid are more completely removed prior to periodic fortification, a wider range of SO3-bearing agents can be applied than previously thought possible. This nondestructive, periodic fortification process effects improvement in the octane rating of the product alkylate while simultaneously extending the service life of the sulfuric acid catalyst by allowing use of the acid to a higher final organic content.