Insights into the Deactivation Mechanism of Heterogeneous Mo/Hβ-Al2O3 Catalysts for Olefin Metathesis
Insights into the Deactivation Mechanism of Heterogeneous Mo/Hβ-Al2O3 Catalysts for Olefin Metathesis
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DOI：
10.1021/jp901103e
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发表时间：
2009-05-14
影响因子：
3.7
通讯作者：
Bao, Xinhe
中科院分区：
文献类型：
--
作者：
Li, Xiujie;Zhang, Weiping;Bao, Xinhe
考察了Mo/H β-Al_2 O_3催化剂上乙烯和丁烯-2歧化制丙烯反应的在线失活。TG，TPO，固态NMR，UV-vis，EPR和XPS技术被用来表征的性质和位置的碳沉积物，以及氧化态的Mo物种的新鲜，使用过的，和再生催化剂。研究发现，即使在低温下，烯烃齐聚反应的副反应也与复分解反应同时发生。大多数含碳物质在反应开始时形成，长链烷烃是主要的焦炭物质。在Mo/H β-Al_2 O_3催化剂中存在三种不同类型的碳质沉积物。随着运行时间形成的大多数脂族烃与催化剂的钼物质有关。活性中心的焦炭中毒和钼物种的深度还原可能是导致催化剂失活的原因。再生催化剂活性的恢复进一步证明了我们提出的失活机理。
On-stream deactivation during metathesis reaction of ethene and butene-2 to propene over Mo/H beta-Al2O3 catalysts was examined. TG, TPO, solid-state NMR, UV-vis, EPR, and XPS techniques were used to characterize the nature and location of carbonaceous deposits as well as the oxidation state of Mo species on the fresh, used, and regenerated catalysts. It is found that side reaction of olefin oligomerization takes place simultaneously with the metathesis reaction even at low temperature. Most of the carbonaceous species are formed at the beginning of the reaction, and long-chain alkanes are the predominant coke species. There are three types of carbonaceous deposits located at different positions within the Mo/H beta-Al2O3 catalysts. Most of the aliphatic hydrocarbons formed with time on stream are associated with molybdenum species of the catalyst. Active sites poisoned by coke and deep reduction of Mo species may be responsible for catalyst deactivation. The recovery of the activity of regenerated catalyst further proves our proposed deactivation mechanism.