SULFATED ZIRCONIA CATALYSTS - ARE BRONSTED ACID SITES THE SOURCE OF THE ACTIVITY

The thermal decomposition products of pyridinium sulfate differ from t hose of pyridinium sulfate supported on zirconia which in turn differs from that of pyridine adsorbed on a sulfated zirconia. Unsupported py ridinium sulfate decomposes to produce pyridine and sulfuric acid, and these subsequently react to produce oxides of carbon and sulfur. Zirc onia that is sulfated and then exposed to pyridine does not release de tectable amount of pyridine during heating in an inert gas; rather the pyridine undergoes oxidation reduction reactions simultaneously to re lease CO2 and sulfur compounds. Pyridinium sulfate supported on zircon ia decomposes upon heating to release pyridine and sulfuric acid, whic h reacts with the zirconia. The desorption of pyridine in one case and only CO2/SOx in the other case suggests that sulfated zirconia does n ot contain Bronsted acidity that can form pyridinium sulfate.