Recovery of hydrocarbons from acid settler bottoms

Claim 1

A process of alkylation of paraffinic hydrocarbons by olefinic hydrocarbons in the presence of sulfuric acid catalyst in a reaction step wherein: a. a reaction mixture of hydrocarbons and sulfluric acid catalyst is withdrawn from said reaction step, b. the sulfuric acid catalyst phase is separated from the hydrocarbon phase in a settling step, c. a major portion of said catalyst phase from said settling step is returned to said reaction step and a minor portion of said catalyst phase is treated to separate absorbed hydrocarbons prior to withdrawing said phase from the alkylation process as a spent acid stream, d. said reaction step and settling step being maintained under sufficient pressure that said reaction mixture, said hydrocarbon phase and said catalyst phase are held in liquid state, e. the pressure is reduced on the hydrocarbon phase from said settling step to vaporize volatile hydrocarbons and thus refrigerate said hydrocarbon phase and f. said refrigerated hydrocarbon phase is passed in indirected heat exchanging relationship with said reaction step to lower the temperature thereof and vaporize further volatile hydrocarbons, g. said hydrocarbon phase from said indirect heat exchanging relationship with said reaction step being passed to a first vapor-liquid separating step wherein a vapor portion of said hydrocarbon phase is separated from a liquid portion thereof and said liquid and said vapor portions being separately removed from said first separating step, the improvement which comprises: h. heating said spent acid stream prior to withdrawing the same from said process and passing said heated stream to a second vapor-liquid separating step to separate said absorbed hydrocarbons from said spent acid, i. returning separated hydrocarbons from said second separating step to said first separating step, j. and withdrawing spent liquid acid from said second separating step.