CHROMIUM-ALUMINUM ORTHOPHOSPHATES .3. ACIDITY AND CATALYTIC PERFORMANCE IN CYCLOHEXENE AND CUMENE CONVERSIONS ON CRPO4-ALPO4 (20-50-WT-PERCENT ALPO4) CATALYSTS IN AQUEOUS AMMONIA

The modification of CrPO4-A catalyst with AlPO4 leads to CrPO4-AlPO4 ( CrAlP-A) catalysts exhibiting not only an increased total acidity but also an increased number of strongest Lewis acid sites as compared to CrPO4 and AlPO4 catalysts. Besides, surface acidity is slightly influe nced by AlPO4 loading (5-50 wt.%). This increased surface Lewis acidit y is responsible for the improved catalytic activity in cyclohexene sk eletal isomerization and cumene dehydrogenation processes. Moreover, t he catalytic activity results can be well interpreted through differen ces in the number and strength of acid sites, measured gas-chromatogra phically, in terms of pyridine and 2,6-dimethylpyridine chemisorbed at different temperatures (573-673 K).