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用NH_3和CO_2的TPD方法观察了化学改性对分子筛催化剂表面酸碱性的影响,并定量讨论了甲苯烷基化反应选择性与酸碱度的关系。结果表明苯环上的反应发生在表面酸度较高而碱度极低的催化剂上,甲苯侧链上的烷基化反应发生在具有足够碱度的催化剂上,而且这些催化剂都还带有较弱的酸度以帮助吸附和稳定苯环分子。表面酸碱度均很低的分子筛上既不能发生苯环烷基化反应,也不能发生侧链上的烷基化反应。还以邻二甲苯的吸附速率的定量数据考察了分子筛孔道结构对反应选择性的影响。
The effect of chemical modification on the surface acidity and basicity of molecular sieve catalyst was observed by the TPD method of NH_3 and CO_2. The relationship between the selectivity and the alkalinity of toluene alkylation reaction was also discussed. The results showed that the reaction on the benzene ring occurred in the catalyst with high surface acidity and very low alkalinity. The alkylation on the side chain of toluene occurred on a catalyst with a sufficient alkalinity, and the catalysts were also weaker Acidity to help adsorb and stabilize benzene ring molecules. Phenol ring alkylation reaction can not occur on the molecular sieve both surface acidity is very low, nor can the side chain alkylation reaction. The effect of the molecular sieve pore structure on the reaction selectivity was also investigated with the quantitative data of the adsorption rate of o-xylene.