MCM-22沸石的孔结构和酸分布特性对苯与丙烯烷基化反应产物分布的影响  

Effect of Pore Structure and Acidic Property of MCM-22 Zeolite on Product Distribution of Benzene Alkylation with Propylene

作　　者：李英霞[1] 陈标华[1] 孟伟娟[1] 李成岳[1] 王文兴[1] 曹钢[2] 

机构地区：[1]北京化工大学可控化学反应科学与技术基础教育部重点实验室,北京100029 [2]燕山石油化工公司,北京102500

出　　处：《催化学报》2003年第7期494-498,共5页

基　　金：国家重点基础研究发展规划项目 (G2 0 0 0 0 480 0 6 )

摘　　要：根据测试结果 ,得到了MCM 2 2和具有相同硅铝比的 β沸石的酸中心数及其分布 ,系统地研究了反应条件对苯与丙烯烷基化反应产物分布的影响 ;结合扩散系数与扩散势能 ,讨论了产物分布与MCM 2 2沸石孔道及酸性质的关系 ,并与 β沸石进行了比较 .苯烷基化反应发生在MCM 2 2沸石的外表面上 ,其空间位阻较小 ;在相同的反应条件下 ,与发生在 β沸石十二元环孔道内的苯烷基化反应相比 ,异丙苯的选择性低 2 %～ 4%,二异丙苯的选择性高 0 5 %～ 5 %,三异丙苯的生成量多 10余倍 .位于MCM 2 2沸石十元环二维正弦波形孔道的B酸中心 ,由于空间位阻大 ,很难发生苯烷基化反应 ,但可发生丙烯齐聚反应 ,故MCM 2 2沸石上有较多的丙烯齐聚物生成 .β沸石上生成正丙苯的量是MCM 2 2沸石上的 3～ 4倍 .MCM-22, having MWW topology, is a zeolite which has unique and unusual pore structure and acidic property on its external surface. In this paper, the total acid sites of MCM-22 ( n(Si)/ n(Al)=15) were measured by means of TG and FT-IR. The B and L acid sites were 375 and 450 μmol/g respectively, and the external surface acid sites were 45 μmol/g. The ratio of initial reaction rate of benzene alkylation over β zeolite (n(Si)/n(Al)=15) to that over MCM-22 was better consistent with the ratio of B acid sites on β zeolite to that on the MCM-22 external surface. It was showed that the benzene alkylation took place on the external surface of MCM-22 and in the 12 MR pore channels of β zeolite, respectively. The distribution of products, including isopropyl benzene(IPB), diisopropyl benzene(DIPB), tri-isopropyl benzene(TIPB), oligomers(Olig) and n-propyl benzene(NPB), was studied under the conditions of n(C 6H 6)/ n(C 3H 6)=2～10, WHSV(C 3H 6)=2.5～30 h -1, p=3.0 MPa and θ=140～210 ℃. On the basis of the diffusion coefficients of the reactants and the energy barriers of the products in MCM-22 and β zeolites, it was found that: (1) owing to that the benzene alkylation took place on the MCM-22 external surface, the selectivity for IPB was lower by 2%～4%, and the amount of DIPB and TIPB was higher over MCM-22 than over β zeolite; (2) the B acid sites located in the 10 MR sinusoidal channels of MCM-22 may not take part in the benzene alkylation owing to the steric effect, but it may take part in oligomerization of propylene, so the oligomers formed over MCM-22 were higher than those over β zeolite; (3) the amount of NPB formed over β zeolite is 3～4 times as that over MCM-22.

关 键 词：MCM-22沸石 Β沸石 苯 丙烯 烷基化 

分 类 号：O643.3[理学—物理化学]