Olefin formation appears to play a key role in n-butane isomerization on sulfated zirconia (SZ). In order to better understand the pathway of the reaction, 1-butene (1-C-4) was added during reaction at low and at high reaction temperatures. Olefin addition, even at the lowest 1-C-4(=)/n-C4 ratio, decreased the activity of the catalyst at 250degreesC, did not eliminate the reaction induction period, and contributed to catalyst deactivation from the beginning of the reaction. However, it shifted the maximum activity to lower time-on-stream (TOS). Butene added for only 90 s at the beginning of the reaction deactivated the catalyst in a manner similar to that in the case where it was added continuously during all TOS. Isotopic transient kinetic analysis (ITKA) showed that although more intermediates were initially formed on the surface with olefin addition, this positive effect was quickly overwhelmed by the negative effect of olefin concentration on deactivation. The positive impact of butene on the reaction was able to be more clearly seen at a lower reaction temperature (150degreesC) when deactivation was not as severe. The positive impact was manifested by an increase in the 5-min TOS reaction rate. Olefin addition also did not eliminate the induction period for reaction at this temperature. Even for these reaction conditions, catalyst deactivation was significant after 30 min TOS due to coke/oligomer formation. The increase in the reaction rate with the addition of olefin was due to an increase in the concentration of surface intermediates; no effect was seen on the average surface residence time for reaction, suggesting that the additional sites created were identical to those formed in the absence of added olefin. Butene added for only 2 min at the beginning of the reaction increased the activity of the catalyst during the next 250 min of reaction time, long after the olefin feed was terminated. Each added 1-butene molecule, thus, contributed to greater n-butane isomerization for many reaction cycles (ca. 700) beyond its elimination from the reactant stream, suggesting that it may have been instrumental in the formation of the additional active sites observed.