PT-SO4(2-)-ZRO2 CATALYSTS - THE IMPACT OF WATER ON THEIR ACTIVITY FOR HYDROCARBON CONVERSION

A series of experiments were conducted to determine the effect of water on the activity of platinum promoted sulfated zirconia catalysts. The initial set of experiments showed that the catalyst exposed to various water partial pressures generated a Type II adsorption isotherm. The activity measurements, as defined by hexadecane conversions, showed that at a ratio of approximately 0.5 mol H2O absorbed per sulfate molecule the water was functioning as a poison. A second set of experiments was designed to generate water in situ by alcohol dehydration for lower ratios of H2O to sulfate than 0.5. These activity measurements showed that water was acting as a poison at these lower ratios and the resulting decline in activity was approximately zero order in water. In addition, the data indicate that the active site for hexadecane conversion is not a Bronsted acid site that is generated by an interaction with added water. (C) 1995 Academic Press, Inc.