磷镁改性的ZSM-5分子筛催化性能研究

研究了磷、镁改性对ZSM-5分子筛的孔结构和酸性的影响。采用甲苯的歧化反应为探针反应,考察了改性后分子筛催化甲苯选择歧化反应的活性和选择性。结果表明，磷、镁单独改性时，随着负载质量分数的增加，转化率逐渐增加，且大于相同工艺条件下HZSM-5的转化率。当磷质量分数达到3％～5％ 或镁质量分数达到1％时，转化率达到最大值，这时对二甲苯为平衡组成，基本没有选择性。磷镁复合改性时，既可以提高催化剂的选择性，又可以使催化剂的活性不至于降得很低。在磷质量分数为9％、镁质量分数为1％时，改性效果最好。

Toluene disproportionation over ZSM-5 zeolite modified by phosphorus and magnesium

The effects of magnesium and phosphorus modification on the pore structure and acidity of ZSM-5 zeolite were studied. The activity and selectivity of the modified ZSM-5 catalysts were investigated using toluene disproportionation to benzene and p -xylene as the model reaction. The results showed that, when one of the two elements was added, conversion of toluene increased with the loading of phosphorus or magnesium, and maximum conversion was obtained at 3%-5% phosphorus loading or 1% magnesium loading, while the selectivity to p -xylene did not increase with addition of phosphorus or magnesium. Simultaneous addition of phosphorus and magnesium increased the selectivity to p -xylene while maintaining reasonable toluene conversion. Optimum modification results were obtained at 9% loading of phosphorus and 1% loading of magnesium.