EFFECT OF PRECIPITATION MEDIUM ON SURFACE-ACIDITY AND CATALYTIC PERFORMANCE OF CHROMIUM ORTHOPHOSPHATES IN CYCLOHEXENE SKELETAL ISOMERIZATION AND CUMENE CONVERSION

The influence of the precipitation medium and thermal treatment of CrP O4 (Cr: P= 1) catalysts on their surface acidity (number and strength distribution) was studied by means of the gas-phase chemisorption of p yridine (PY) and 2,6-dimethylpyridine (DMPY) at 573 and 673 K. In addi tion, cyclohexene skeletal isomerization (CSI) and cumene conversion ( CC), were selected as dynamic methods for surface acid characterizatio n. Catalysts obtained in propylene oxide-aqueous ammonia exhibited a h igher number and strength of acid sites and, hence, greater activity i n CSI and CC processes, than catalysts obtained in propylene oxide or aqueous ammonia exclusively. Moreover, cumene dehydrogenation (to alph a-methylstyrene) always predominated over cumene dealkylation (to prop ylene and benzene) and accounted for 100% selectivity of CrP-A and CrP -P catalysts. Furthermore, a correlation between surface acidity and c atalytic activity was found.