Mo/HZSM-5催化剂上甲烷无氧芳构化反应——HZSM-5分子筛脱铝的影响  

Methane Dehydroaromatization over Mo/HZSM-5 Catalyst:Effect of Dealumination of HZSM-5 Zeolite

作　　者：宋一兵[1] 孙长勇[2] 吴燕青[1] 申文杰[2] 林励吾[2] 

机构地区：[1]汕头大学化学系,广东汕头515063 [2]中国科学院大连化学物理研究所催化基础国家重点实验室,辽宁大连116023

出　　处：《催化学报》2007年第4期371-376,共6页

基　　金：国家自然科学基金(20203012);广东省自然科学基金(06027205)

摘　　要：采用两种不同的脱铝方法对HZSM-5分子筛进行了预处理,并利用MAS NMR和吸附吡啶的FT-IR对分子筛的结构和酸性质进行了表征,考察了分子筛的脱铝程度对Mo基催化剂上甲烷芳构化反应性能的影响.结果表明,HZSM-5分子筛的酸性过强或B酸量不足,均会导致催化剂严重积炭,但积炭成因不同.母体HZSM-5分子筛上的强B酸中心的存在可促使催化剂上反应中间物种深度脱氢,造成催化剂在反应过程中严重积炭.经水热处理的HZSM-5分子筛,骨架铝脱出严重,造成B酸活性中心不足以及部分微孔阻塞,不利于C2中间物种芳构化,导致芳烃选择性显著降低.经高温N2处理的HZSM-5分子筛,骨架铝脱出相对缓和,在消除母体分子筛上强B酸中心的同时,保留了较多的弱B酸中心,既可满足C2中间物种芳构化反应的需要,又可有效抑制催化剂积炭,导致甲烷芳构化反应性能显著改善.Two dealumination methods were used to modify the framework composition of the HZSM-5 zeolite. The structure and acidity of dealuminated zeolite samples were investigated by MAS NMR and FT-IR. It was found that the catalytic performance of the Mo/HZSM-5 catalyst for methane dehydroaromatization was closely related to the acidity of the HZSM-5 zeolite. On the parent zeolite with n （Si）/n （Al）≈27, the presence of superfluous strong Bronsted acid sites caused severe coke deposition during the reaction. Hydrothermal treatment of the parent zeolite extracted tetrahedral Al from the framework and thus led to a significant reduction in the number of Bronsted acid sites. The formation of aromatics over this hydrothermally treated zeolite was suppressed owing to the deficiency of acid sites available for the aromatization of C2 intermediates. High-temperature N2 treatment induced mild dealumination of HZSM-5, destroyed the origin strong Bronsted acid sites, but retained sufficient weak acid sites. This treatment effectively restrained coke deposition and satisfied the requirement of the aromatization of C2 intermediates during the reaction. Therefore, a remarkable improvement in the catalyst durability and selectivity for aromatics was observed.

关 键 词：甲烷 芳构化 钼 HZSM-5分子筛 负载型催化剂 脱铝 水热处理 高温氮气处理 

分 类 号：O643.36[理学—物理化学]