助催化剂对甲苯歧化与烷基转移催化剂性能的影响

Effect of Promoter on the Acidity and Catalytic Performance of Catalysts for Toluene Disproportionation and Transalkylation

采用助催化剂对丝光沸石进行改性,通过红外光谱(FT-IR)方法表征了该改性分子筛制备的催化剂样品表面酸性的变化,并探讨了酸性变化对甲苯歧化与烷基转移反应催化活性的影响。结果表明,助催化剂 WO3的加入能有效地调节催化剂表面酸性,经氢气还原后催化剂B酸量随助催化剂量增加而增加,且与助催化剂相对含量呈对数关系;而L酸量随助催化剂相对含量的增加先上升,随后趋于平稳;催化剂的反应活性随助催化剂含量的增加而增加,但副反应也随之加大。

The effect of tungsten nitrate, used as a promoter, on the surface acidity and catalytic performance of the mordenite catalysts were investigated by means of FT-IR measurements, pyridine temperature programmed desorption and lab-scale catalyst evaluation equipments. It was found that the ratio of Bronsted acid sites to Lewis acid sites increased proportionally with the amount of tungsten nitrate physically mixed with the main components of catalysts. As a result, the catalyst activity for toluene disproportionation and transalkylation also increased with this ratio at the expense of the selectivity reduction. For overcoming this disadvantage, the impregnating method was used to prepare the catalyst. The catalyst performance indicated that the activity increased dramatically while the selectivity decreased slightly as the amount of tungsten nitrate added was much low- er than that in the case of physical mixing.