ZSM-5分子筛酸性修饰及探针分子表征

采用柠檬酸、硫醚、苯胺、二苯胺、磷酸二氢铵及硅油作为改性试剂对二甲苯异构化专用HZSM-5分子筛进行液相浸渍改性，结合甲苯、邻二甲苯、间二甲苯、乙苯及间二异丙苯的脉冲反应表征，对各种改性手段的效果进行评估。各种改性方法对微孔体积和比表面积的影响很小，均减弱了酸性，对L酸的影响大于B酸。5种探针反应结果表明:柠檬酸改性强化了分子筛酸性，提高了歧化/异构化活性；磷酸二氢铵改性提高了歧化和脱乙基反应活性；苯胺、二苯胺、硫醚改性手段部分钝化了分子筛酸性，降低了歧化异构化活性；随着改性剂分子尺寸的增大，钝化外表面酸性越明显，从而改变分子筛孔内外的酸位分布，产生不同程度的择形效果；硅油改性充分地钝化了外表面酸性，形成最明显的择形效应。

MODIFICATION OF ACIDITY OF ZSM-5 ZEOLITE AND ITS ISOMERIZATION PROPERTIES

The evaluation of modified HZSM-5 was conducted by series of pulse reactions, using meta, ortho-xylene, toluene, ethylbenzene and meta- biisopropylbenzene. The modification of HZSM-5 was carried by liquid impregnation using citric acid, sulfide, aniline, diphenylamine, ammonium dihydrogen phosphate and silicone oil. The impacts of various modification methods on pore volume and surface area are weak, shown by BET. FTIR analysis showed that each modification processes are weakened acidity, the impact on L acid is greater than B acid. Five probe-reaction experiments indicated: the aniline, diphenylamine, sulfide and ammonium dihydrogen phosphate modification can enhance the shape-selectivity, and inhibit the xylene isomerization, the citric acid enhanced isomerization, disproportionation, reduced the selectivity, the silicone-modified passivated outer surface acidity, retained the activity in the channels.