paraffin alkylation using solid , particulate catalyst is carried out by preparing an alkane - catalyst mixture in a wash zone , passing the alkane - catalyst mixture to a plug flow reactor where a minor amount of olefin is introduced to contact the alkane - catalyst mixture and react to form alkylate and the alkane - catalyst - alkylate mixture is passed through the reactor with a minimum of back mixing to restrict the reaction of alkylate with olefin , thus substantially preventing polymerization . the alkane - catalyst - alkylate mixture , substantially free of olefin is passed to a disengaging zone where the liquid is removed and the solid particulate catalyst is recovered and returned to the wash zone for recycle . the alkane is present in the reactor in sufficient molar excess to react substantially all of the olefin . any unreacted isoalkane is recycled to the reactor with make - up isoalkane added to maintain the molar excess . the preferred catalyst is an acid washed silica treated with antimony pentafluoride and more preferably treated with alkane at low temperature , e . g . - 30 ° to - 160 ° c .