Shape selective conversion of 1,2,4-trimethylbenzene over zeolite NU-87

被引:59
作者
Park, SH
Rhee, HK [1 ]
机构
[1] Seoul Natl Univ, Sch Chem Engn, Kwanak Ku, Seoul 151742, South Korea
[2] Seoul Natl Univ, Inst Chem Proc, Kwanak Ku, Seoul 151742, South Korea
关键词
NU-87; MCM-22; 1,2,4-trimethylbenzene; disproportionation; isomerization;
D O I
10.1016/S0920-5861(00)00468-5
中图分类号
O69 [应用化学];
学科分类号
081704 ;
摘要
The catalytic properties of zeolite NU-87 were investigated in the conversion of 1,2,4-trimethylbenzene in view of the product selectivity. To examine the catalysis by external acid sites, experiments were conducted over NU-87 with external surface poisoned by 1,1,1,3,3,3-hexamethyldisilazane. For comparison, the results obtained over MCM-22, which has a similar pore structure, are also included. Both disproportionation (to xylene and tetramethylbenzene) and isomerization (to 1,2,3- and 1,3,5-isomers) take place over NU-87. Under the present conditions, it is found that the disproportionation proceeds largely within the micropores of NU-87, while the isomerization reaction occurs mainly on the external surface. The distribution of xylene isomers is thermodynamically controlled inside the pores, whereas amongst tetramethylbenzene isomers, the 1,2,4,5-isomer is selectively produced through the channel system. The bully product, 1,2,3,5-tetramethylbenzene (or 1,3,5-trimethylbenzene), is severely hindered from diffusing through the channel system of NU-87. However, 1,2,3,4-tetramethylbenzene and 1,2,3-trimethylbenzene diffuse out of the micropores to a certain extent. In the case of MCM-22, the conversion of 1,2,4-trimethylbenzene hardly proceeds within the micropores. It is evident that NU-87 has larger pores and thus higher accessibility to 12-MR cavities than MCM-22. (C) 2900 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:267 / 273
页数:7
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