INVESTIGATIONS ON THE CHARACTERISTICS, SURFACE, ACIDITY ACID STRENGTH DISTRIBUTION AND CATALYTIC PROPERTIES OF THE ZINC-SUBSTITUTED ALUMINOPHOSPHATE OF TYPE-36 MOLECULAR-SIEVE

The large pore zinc-incorporated aluminophosphate with ATS topology (ZAPO-36) was prepared and characterized by using various techniques. The surface composition determination by X-ray photoelectron spectroscopy analysis revealed that the concentration of zinc and phosphorus are higher on the surface than in the bulk of ZAPO-36 catalyst. The observed binding energy of Zn 2P3/2 corresponds to that of Zn 2P3/2 in ZnO. The site energy distribution on the zinc aluminophosphate has been found to be very broad. ZAPO-36 possesses a greater number of strong acid sites than AlPO4-5, SAPO-5, MAPO-5 and MAPO-46. The zinc aluminophosphate shows a significant catalytic activity in the cumene, 3-methylpentane, isooctane, cyclohexane, cycloheptane, 1,3,5-trimethylbenzene, 1,2,3,4-tetramethylbenzene, toluene, methanol conversion reactions at 673 K. The catalytic activities of AlPO4-5, ZAPO-36, MAPO-36 and H-ZSM-5 have been compared in the methanol, 3-methylpentane and toluene conversion reactions. In the toluene disproportionation reaction, ZAPO-36 exhibited a higher catalytic activity than the AIPO4-5, MAPO-46 and H-ZSM-5. The deactivation behaviours of ZAPO-36 and MAPO-36 in the cracking of cumene were studied.