Chromium-aluminium orthophosphates, III. Acidity and catalytic performance in cyclohexene and cumene conversions on CrPO4−AlPO4 (20–50 wt.% AlPO4) catalysts obtained in aqueous ammonia

Abstract

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 influenced by AlPO4 loading (5–50 wt.%). This increased surface Lewis acidity is responsible for the improved catalytic activity in cyclohexene skeletal isomerization and cumene dehydrogenation processes. Moreover, the catalytic activity results can be well interpreted through differences in the number and strength of acid sites, measured gas-chromatographically, in terms of pyridine and 2,6-dimethylpyridine chemisorbed at different temperatures (573–673 K).