Aromatic Transformations Over Mesoporous ZSM-5: Advantages and Disadvantages
Aromatic Transformations Over Mesoporous ZSM-5: Advantages and Disadvantages
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DOI：
10.1007/s11244-010-9606-5
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发表时间：
2010-10
影响因子：
3.6
通讯作者：
Z. Musilová;N. Žilková;Sang-Eon Park;J. Čejka
中科院分区：
文献类型：
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作者：
Z. Musilová;N. Žilková;Sang-Eon Park;J. Čejka
考察了介孔分子筛ZSM-5在甲苯歧化、甲苯与异丙醇烷基化、对二甲苯与异丙醇烷基化反应中的催化行为，以了解介孔的存在对甲苯歧化反应的影响。合成了三种具有相似硅铝比的ZSM-5沸石分子筛(常规的一种和两种介孔体积不同的中孔分子筛)，并对其酸性(内外)和微孔/中孔体积进行了表征。三个样品在Brnsted和Lewis酸中心的类型和浓度以及它们在沸石孔道或沸石晶体外表面的位置方面没有明显的差异。甲苯和对二甲苯的转化率随着ZSM-5分子筛中孔体积的增加而增加，而对个别产物的选择性则取决于反应类型。总体而言，由于分子在介孔ZSM-5催化剂上的接触时间较短，甲苯歧化反应中二甲苯总和、甲苯烷基化反应中异丙基甲苯总和和对二甲苯烷基化反应中1-异丙基-2，5-二甲苯的选择性提高。相反，由于介孔的存在，对位选择性随着扩散路径的缩短而降低。
Catalytic behavior of mesoporous ZSM-5 was investigated in toluene disproportionation, toluene alkylation with isopropyl alcohol, andp-xylene alkylation with isopropyl alcohol to understand the effect of the presence of mesopores. Three ZSM-5 zeolites (conventional one and two mesoporous differing in the mesopore volume) having similar Si/Al ratio were synthesized and characterized as for their acidity (internal and external) as well as their micropore/mesopore volume. No substantial differences among three samples were observed as for the type and concentration of Brønsted and Lewis acid sites as well as their location in zeolite channels or on external surface of zeolite crystals. Conversions of toluene andp-xylene increased with increasing volume of mesopores in ZSM-5 zeolite while the selectivity to individual products depended on the type of reaction. In general, selectivity to sum of xylenes in toluene disproportionation, sum of isopropyltoluenes in toluene alkylation and to 1-isopropyl-2,5-dimethylbenzene inp-xylene alkylation increased due to a shorter contact time molecules spent in mesoporous ZSM-5 catalysts. In contrast,para-selectivity decreased as diffusion pathways were shorten due to the presence of mesopores.