直链烯烃在裂化催化剂基质上的反应机理研究  

REACTION MECHANISM OF NOMAL OLEFIN OVER MATRIXES OF FCC CATALYST

作　　者：王伟 宋海涛[2] 蒋文斌[2] 达志坚[2] 

机构地区：[1]南阳石蜡精细化工厂,南阳473132 [2]石油化工科学研究院

出　　处：《石油炼制与化工》2004年第10期34-40,共7页Petroleum Processing and Petrochemicals

基　　金：国家重点基础研究发展规划项目(G2000048001)。

摘　　要：用溶胶-凝胶法制备了一系列FCC催化剂的基质材料SiO2Al2O3,采用XRD、BET及IR对其结构和酸性特征进行了表征。在FCC操作条件下,以n-C7=-1为模型化合物,考察了反应产物分布与基质材料酸中心特性的关联,提出了n-C7=-1的裂化反应网络,对n-C7=-1的异构化、氢转移、芳构化等二次反应机理进行了探讨。结果表明:异构化反应过程同时以单分子和双分子两种机理进行,但双分子反应选择性较低;氢转移反应不仅与基质的酸中心密度有关,对酸类型的影响更为敏感,在只有L酸的基质上,氢转移以Rideal机理进行,其活性随酸中心密度呈线性增加;在既有B酸又有L酸的基质上,氢转移更倾向于L-H机理,其活性随酸中心密度呈指数增加;烯烃二次反应之间选择性的竞争很大程度上取决于B酸与L酸在总酸量中的分配;以烯烃在B酸与L酸上形成结构不同的正碳离子为前提,提出了两种正碳离子进一步反应的机理模型,并较好地解释了烯烃的反应机理与产物分布。A series of FCC catalyst matrixes, SiO2-Al2O3, were prepared by sol-gel method, the structural characterization and acid site measurements of the matrixes were carried out by XRD, BET and IR. Under FCC operating conditions, heptene-1 was used as the model compound to determine the relations between product distribution and surface acid sites. A reaction scheme of heptene-1 was put forward, and the reaction mechanism of the secondary reactions such as isomerization, hydrogen transfer and aromatization was discussed. It was found that, skeletal isomerization of heptene-1 proceeded via both monomolecular and bimolecular mechanisms, but the selectivity of bimolecular isomerization was low. Higher density of strong acid sites was available for hydrogen transfer reaction. The type of the acid sites influenced the hydrogen transfer reaction more apparently. On the matrix only with Lewis acidsites, hydrogen transfer reaction proceeded by Rideal mechanism, and its activity was linearly increased with the increase of the density of acid sites. However, on matrixes with not only Lewis acid but also Bronsted acid sites, hydrogen transfer was inclined to proceed by L-H mechanism, and its activity was exponentially increased with the increase of the density of acid sites. The selectivity competition among olefin secondary reactions was depended by the B/L acid ratio. Based on the different structural carbonium ions formed by olefins over Bronsted acid and Lewis acid, models of further reaction mechanism for two type carbonium ions were proposed, and the reaction mechanism of olefin and its product distribution were explained.

关 键 词：链烯烃 氢转移 反应选择性 酸类型 反应机理 产物分布 操作条件 裂化催化剂 二次反应 FCC催化剂 

分 类 号：O643.3[理学—物理化学]