n(SiO_2)/n(Al_2O_3)对MCM-22分子筛的结晶度及烷基化性能的影响

Influence of n(SiO_2)/n(Al_2O_3) on the Crystallinity and Alkylation Performance of MCM-22 Zeolite

试验考察了n(SiO2)/n(Al2O3)=12～90的范围内,硅铝比对MCM22分子筛的结晶度及烷基化性能的影响。结果表明,在固定结晶时间5天、结晶温度150℃的条件下,当n(SiO2)/n(Al2O3)=30～90时容易得到结晶度较高的纯相样品,随着硅铝比的增大,结晶度略有降低;B酸量呈现先增加后降低的趋势,L酸量基本呈现下降趋势。当n(SiO2)/n(Al2O3)=12～30时,水硅比的范围更窄,只有当n(H2O)/n(SiO2)≥25时才能得到纯相样品,但结晶度降低。在苯与丙烯的烷基化反应中,相同条件下n(SiO2)/n(Al2O3)=18～30时,MCM22分子筛的催化活性最高,降低或增大硅铝物质的量比,活性逐渐降低。

Experiments showed that in the synthesis of MCM - 22 zeolite, the product with high crystallinity could be easily prepared when n（SiO2）/n（Al2O3） ranged from 30 to 90, and the product with low crystallinity could be obtained only under the condition of n（H2O）/n（SiO2）≥25 when n（SiO2）/n（Al2O3） ranged from 12 to 30.The alkylation of benzene with propylene was investigated over MCM- 22. The results indicated that the zeolite with n（SiO2）/n（Al2O3） from 18 to 30 had the highest activity, and the activity gradually declined when n （ SiO2 ）/n （ Al2O3 ）increased or decreased beyond the range. At the same time,the selectivity of cumene gradually increased. When n（SiO2）/n（Al2O3） ranged from 30 to 90, the amount of B acid first increased and then decreased, while the amount of L acid basically decreased.