SULFATED ZIRCONIA AS A HYDROCARBON CONVERSION CATALYST

Platinum containing sulfated zirconia is a more active catalyst for hydrocarbon isomerization and cracking than most, if not all, zeolite cracking catalysts. A survey of the literature data suggests that the preparation technique, initial calcination and final catalyst treatment play important roles in determining catalyst activity. The final treatment probably is the most important and least controlled step in most studies to date. Whether the catalytic site involves Lewis or Bronsted acidity is debated; our data indicate Bronsted acidity as more likely. The role of a supported metal, e.g., Pt, is to provide a hydrogenation role but many attribute a second role for it in generating acidity through hydrogen spillover. For hexadecane conversions, increasing the hydrogen pressure increases the cracking to lower molecular weight hydrocarbons. The presence of small amounts of hydrogen donors are claimed to improve isomerization selectivity.