The deactivation of sulfated zirconia catalysts in the isomerization of n-butane has been studied using a combined TGA/FT-IR technique. Following deactivation at 200 degrees C in the n-butane isomerization reaction, two SO2 desorption maxima centered at 600 degrees C and at 850 degrees C were observed under a flow of N-2. Coincidental with the low temperature desorption maximum of SO2 centered at 600 degrees C, a CO2 desorption maximum was also observed. Under an oxygen flow, the coke could be selectively burned off without removing the low temperature sulfur, which results in the complete restoration of the catalytic activity. In a N-2 flow, both CO2 and SO2 (low temperature) were removed, The loss of the low temperature sulfur results in a catalyst which is inactive in the isomerization of n-butane. A change in the crystal phase was not observed by XRD as result of the loss of the sulfur evolved at 600 degrees C.