ZSM-22分子筛催化甲苯甲醇烷基化反应的研究

通过浸渍法对ZSM-22分子筛进行SiO₂和La₂O₃改性，制备了一系列催化剂。采用固定床微型连续流反应器对催化剂的反应性能进行了评价。考察了ZSM-22、SiO₂和La₂O₃改性ZSM-22对甲苯甲醇烷基化反应性能的影响。实验发现，ZSM-22催化甲苯甲醇烷基化反应的产物中，对二甲苯的选择性远高于间位和邻位异构体的选择性,而改性后的催化剂上目标产物对二甲苯的选择性得到提高，但反应活性下降。随SiO₂和La₂O₃负载量的增加，甲苯的转化率逐渐降低，对二甲苯选择性逐渐提高，其中,以La₂O₃改性后对二甲苯选择性提高较明显。SiO₂和La₂O₃复合改性后，甲苯的转化率高于La₂O₃单独改性的结果，而对二甲苯选择性与La₂O₃单独改性结果相近，并且，二甲苯的选择性略有提高。

Methylation of toluene with methanol over ZSM-22 zeolite catalysts

ZSM-22 zeolite catalysts modified with different contents of SiO2 or La2O3 were prepared by impregnation method. Methylation of toluene with methanol to p-xylene was carried out over these catalysts by means of a fix-bed flow reactor. The results showed that selectivity to p-xylene was higher than m- and o- isomers over ZSM-22 catalysts. The modified catalysts exhibited higher selectivity to p-xylene but lower toluene conversion than ZSM-22. Toluene conversion declined while selectivity to p-xylene increased with SiO2 or La203 content. ZSM-22 catalysts modified by La2O3 had the most remarkable increase in selectivity. Toluene conversion over ZSM-22 modified by La2O3 and SiO2 combined was higher than over those modified solely by La2O3, while selectivity to p-xylene was comparable in both case, with slight increase in selectivity to xylene.