酸碱改性ZSM-5分子筛及其催化苯甲醇烷基化反应
Acid-base modified ZSM-5 zeolites and its catalytic alkylation of benzene and methanol
魏书梅
作者单位：中国石油乌鲁木齐石化公司研究院
中文关键字：酸碱改性；ZSM-5；介孔；苯甲醇烷基化
英文关键字：
中文摘要：采用酸碱改性对ZSM -5分子筛进行了改性，通过XRD、 SEM、N2吸-脱附和NH3-TPD等手段对处理前后的样品进行了表征，并研究改性分子筛催化剂的苯甲醇烷基化催化性能。结果表明：适宜的酸碱改性浓度分别为0.1M和0.3M，通过碱改性，可以脱除分子筛部分骨架硅，再由酸液洗涤，可去除催化剂表面的附着物，引入一定量的介孔，比表面积增大，暴露出更多的活性位。与改性之前相比，介孔体积由0.10m3/g提高至0.47m3/g，比表面积由385m2/g增大至452m2/g，酸量基本保持不变；在460℃，总质量空速2.0 h-1，苯与甲醇摩尔比1:1，0.5MPa（H2）时，最优催化剂可连续运行2016h，苯转化率最大为63.31%，甲苯和二甲苯选择性最大为95.71%，对二甲苯选择性为26.89%，具有良好的苯甲醇烷基化催化性能和稳定性。
英文摘要：ZSM -5 zeolites were modified by acid and alkaline liquor, and the samples were characterized by XRD, SEM, N2-adsorption-desorption and NH3-TPD, then the modified ZSM-5 zeolites were studied as the catalysts for methanol and benzene methylation reaction. The results showed that the appropriate acid and alkali concentration was 0.1M and 0.3M respectively.
The skeleton silicon of the ZSM-5 zeolites can be removed by alkali modification and the attachment on the surface of ZSM-5 zeolite was washed by acid solution with increasing mesoporous volume and specific surface area, then more active sites were exposed. The mesoporous volume was increased from 0.10m3/g to 0.47m3/g and specific surface area were increased from 385m2/g to 452m2/g, and the acid content was almost unchanged. Under the conditions of 460 ℃, 0.5 MPa (H2) and WHSV 2 h-1, n(methanol): n(benzene)=1:1, the optimal catalyst can run for 2016h continuously, with the maximum benzene conversion rate of 63.31%, the maximum selectivity of toluene and xylene of 95.71%, and the selectivity of p-xylene of 26.89%, therefore it had good catalytic performance and stability for methanol and benzene methylation reaction.