锌磷酸铝分子筛ZAPO-34的合成

SYNTHESIS OF ZINC ALUMINOPHOSPHATE MOLECULAR SIEVE ZAPO-34

硅磷酸铝分子筛SAPO-34是SAPO-n系列分子筛中的一员,结构类型与菱沸石(Cbabazite)相当,属小孔沸石类,孔口大小为4.3(?),孔体积为0.42cm^2/g。1985年我们合成了这种分子筛,作为甲醇转化制低碳烯烃的催化剂。

A novel molecular sieve ZAPO-34 was prepared by hydrothermal synthesis. The appropriate composition zone of the formation of pure ZAPO-34 given in Zn-Al-P phase diagram is: ZnO/P_2O_5=0.5-1.5, ZnO/ A1_2O_3=0.4-2.0 and A1_2O_3/P_2O_5=2.0-7.5. The influence of pH of the reaction mixture on the characteristics of the product phase was investigated. It was found that the product is pure ZAPO-34 when pH=4.5-6.0. The apparent activation energies for nucleation and crystallization are 43.51 kJ/mol and 82.19 kJ/mol respectively. The thermal stability of the samples was investigated by high temperature XRD. It was found that the temperature of structural collapse of the samples decreased with increasing ionic radii of hetero-atoms in the samples, and that for pure ZAPO-34, the temperature of structural collapse decreased with increasing ZnO content in it. In the reaction of methanol conversion to hydrocarbons over HZAPO-34 the selectivity to C_2^-is predominant and there are almost no C_4^+.