摘要
Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）.Various parameters for preparing catalysts were changed to investigate the suitable conditions.The resulting cata-lysts were tested in a pressured fixed bed reactor and characterized by SEM （scanning electron microscopy）.The conversion of toluene and para-xylene selectivity were influenced remarkably by the n（SiO2）/n（Al2O3） ratio of ZSM-5 zeolite,the type and amount of deposition agent,acid and solvent used,and the time and cycle of deposition treatment.TEOS was proved to be a more efficient agent than the conventional polysiloxanes when the deposition amount was low.The catalyst prepared at the suitable conditions exhibited a high para-xylene selectivity of 91.1% with considerable high conversion of 25.6%.SEM analyses confirmed the formation of a layer of amorphous silica on the external surface of ZSM-5 zeolie crystals,which was responsible for the highly enhanced shape-selectivity.
为甲苯的 disproportionation 的形状选择的催化剂被塑造柱体的 ZSM-5 沸石 extrudates 的修正与 TEOS (tetraethyl orthosilicate ) 与化学液体免职准备。为准备催化剂的各种各样的参数被改变调查合适的条件。产生催化剂在一个迫使的固定的床反应堆被测试并且由 SEM (扫描电子显微镜学) 描绘了。甲苯和帕拉二甲苯选择的变换被免职代理人，酸和溶剂的 ZSM-5 沸石，类型和数量的 /n (Al2O3 ) 比率使用了的 n (SiO2 ) 显著地影响，并且免职处理的时间和周期。当免职数量是低的时， TEOS 被证明比常规 polysiloxanes 是一个更有效的代理人。以合适的条件准备的催化剂与 25.6% 的可观的高变换展出了 91.1% 的一种高帕拉二甲苯选择。SEM 分析在 ZSM-5 zeolie 晶体的外部表面上证实了非结晶的硅石的层的形成，它为高度提高的形状选择负责。
基金
Supported by the Key Natural Science Foundation for Universities of Jiangsu Province（06KJA53012）
the National Natural Science Foundation of China（20776069 20976084）
