晶化条件对HZSM-5分子筛合成收率和性能的影响

考察了SiO2-Al2O3-TPABr-NH3·H20—H2O体系晶化时间、晶化温度和原料用量等对合成HZSM-5性能的影响。当n（SiO2）：n（Al2O3）=100、n（TPABr）：n（SiO2）=0．1、n（NH3）：n（SiO2）=1．5、n（H2O）：n（SiO2）=22和晶种添加质量分数为4％时，180℃静态晶化72h，合成收率与相对结晶度分别为10．1％和99．8％，对应理论收率为11．4％，合成收率与理论收率比为0．89。当投料n（SiO2）：n（A1203）从50增加到400，合成收率与结晶度分别超过8．9％和82．8％，合成收率与理论收率比为0．76—0．89；样品酸量随着n（SiO：）：n（Al2O3）的增加逐渐减小，比表面积为405m2·g-1，合成样品HZSM-5对甲醇制烯烃反应具有良好的酸催化活性。设定反应条件，采用投料n（SiO2）：n（AlO3）=250的样品，甲醇转化率、丙烯选择性和C=2～C=4选择性分别为100％、39．27％和62．01％。

Effects of crystallization conditions on the yields and properties of HZSM-5 molecular sieves

In SiO₂-Al₂O₃-TPABr-NH₃·H₂O-H₂O system,the effects of hydrothermal crystallization time and temperatures,and raw material amounts on the yields and properties of as-synthesized HZSM-5 molecular sieve were investigated.The results showed that the yield and relative crystallinity of as-synthesized samples were 10.1% and 99.8%,respectively,under the condition as follows:n(SiO₂)∶n(Al₂O₃)=100,n(TPABr)∶n(SiO₂)=0.1,n(NH₃)∶n(SiO₂)=1.5,n(H₂O)∶n(SiO₂)=22,seed crystal amount 4%,crystallization temperature 180 ℃ and crystallization time 72 h.The corresponding theoretical yield was 11.4%,and the ratio of the yield of as-synthesized samples to the theoretical yield was 0.89.As n(SiO₂)∶n(Al₂O₃) of the raw material enhanced from 50 to 400,the yield and crystallinity of the as-synthesized samples remained more than 8.9% and 82.8%,respectively,and the ratio of as-synthesized sample yield to the theoretical yield was 0.76-0.89.The acid amount of the as-synthesized samples decreased gradually with the increase of n(SiO₂)∶n(Al₂O₃) of the raw material.The as-synthesized HZSM-5 molecular sieve with BET surface area of 405 m²·g^-1 exhibited good acid catalytic activity for methanol-to-olefins reaction.At the set condition,methanol conversion,the selectivity to propylene and C₂⁼-C₄⁼ light olefins were 100%,39.27% and 62.01%,respectively,using HZSM-5 molecular sieve catalyst prepared with the raw material of n(SiO₂)∶n(Al₂O₃)=250.