Alkylation of isobutane feeds contg. reactive impurities - with prior impurity removal by contact with spent catalyst

摘要

The alkylation of an isobutane feedstock contaminated with impurities reactive with AlCl3 is carried out by (a) reacting a recycled pure isobutane stream with an ethylene stream contg. 1-3C n-paraffin impurities, in the presence of an AlCl3-hydrocarbon complex catalyst and HCl as activator, (b) separating the effluent into a hydrocarbon phase and a catalyst phase, (c) recycling a major part of the catalyst phase to stage (a); (d) fractionating the hydrocarbon phase in a debutaniser to give a C5+ alkylate fraction and a recycle fraction contg. isobutane and minor amts of EtCl, 1-4C n-paraffins and unreacted ethylne, (e) recycling a major part of the recycle fraction to stage (a), (f) contacting a minor part f the catalyst phase from (b) with the fresh isobutane feedstock (contg. 3-4C n-paraffin diluents) so that the reactive impurities react with the AlCl3 to form soluble cpds. (g) separating the effluent from (f) into a catalyst phase and an impurity-free isobutane phase, contg 3-4C n-paraffins, (h) fractionating the isobutane phase from (g) and a mino part of the recycle phase from (d) in a depropaniser to give a 1-3C fraction and a bottoms fraction contg a major amt. of isobutane and a minor amt. of n-butane and EtCl, (i) fractionating the bottoms fraction to isolate a pure siobutane fraction, and (j) recycling the latter to stage (a). Reactive impurities such as H2O, mercaptans, dines and acetylenes are removed by reaction with the spent catalyst before the isobutane is contacted with the working catalyst, thus increasing the effectiveness of the catalyst.