A solid superacidic Nafion-H polymer was examined as a catalyst for isobutane/2-butene alkylation and compared with a cerium-exchanged Y zeolite. Both catalysts demonstrate initial alkylation activity with rapid decrease in alkylation selectivity. The total product distributions were found to be significantly different after three hours of reaction. Nafion-H showed less selectivity towards iso-octanes, but formed relatively more 2,2,4-trimethylpentane. The differences between the two catalysts suggest dissimilar favoured reaction mechanisms.