Abstract: By means of infrared spectra and temperature programmed desorption, the surface acidity of magnesium alumlnophosphate molecular sieve(MAPO-5) was studied. The ion-exchange isotherm was measured for Ni²⁺-MAPO-5 system at 94℃. Catalytic hydrogenation activity over MAPO-5 and Ni-MAPO-5 catalysts was examined using ethylene hydrogenation as a probe reaction. The results indicate that the turnover number is increased with the increasing of reduction temperature for Ni²⁺-MAPO-5 catalyasts. The highest activity can be obtained on the catalysts reduced at 3201℃. and their activities decrease when the temperature is further increased. It may be found that the turnover number of ethylene on Ni atoms has unchanged whether the amount of Ni on the catalysts varied or not, within its concentration range, 0.4～3.2% wt. MAPO-5 has no activity for ethylene hydrogenation. The catalytic cracking activity of a-hexadecane over the same catalysts was also tested. The experimental results showed that the activities of Ni²⁺-MAPO-5 and MAPO-5 catalysts much higher than those of AlPO₄-5 perhaps is due to the high acidities of the two types of the catalysts(MAPO-5).

Key words: Magnesium aluminophosphate, Molecular sieve, Catalytic hydrogenation, Catalytic cracking