The alkylation of isobutane with butene catalyzed by the supported 12-tungstophosphoric acid catalyst, 20%H 3PW 12O 40/SiO 2, has been investigated and an important and interesting experimental phenomenon has been found out occasionally. That is, when a trace amount ( 0 019?2% in mass fraction) of hydrogen fluoride is added into the feedstock, the yield of the target alkylation product, trimethyl pentane, and the total concentration of C 8 alkanes in alkylate are enhanced greatly under the superc...