Three commercial ion-exchange resin based catalysts were compared under different temperature and liquid-volume hourly space velocity (LHSV) in the isobutene (IB, C4) dimerization reaction using a plug flow reactor in the absence of any selectivity enhancing component. High IB conversion for all catalysts was obtained at or higher than 50 degrees C. But, diisobutene (DIB, C8) selectivity decreased with the increase of temperature. High C8 selectivity was observed with LHSV higher than 1.5 at 50 degrees C. The best catalytic performance of the three resins did not show obvious differences. The effect of the selectivity enhancers on the stability of the resins was also studied. Desulfonation was observed in the C4 dimerization reaction when water or the commonly used enhancer tert-butyl alcohol (TBA) was added to the feed. The deactivation of catalyst resulted in decrease of both IB conversion and C8 selectivity. Fourier Transform Infrared spectroscopy showed that desulfonation happened in both para and ortho positions of the sulfonated benzene rings. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013