反应条件对正庚烷在Mo_2C/Hβ上异构产物的影响

Influence of Reactive Conditions on n-Heptane Isomerization Products Over Mo_2C/Hβ Catalyst

以正戊烷为碳源,采用程序升温法制备了Hβ沸石分子筛负载碳化钼催化剂,并进行X射线衍射(XRD)表征。在固定床微型反应器内进行正庚烷在该催化剂上的异构化反应,考察反应条件对正庚烷异构化产物分布的影响,并探讨正庚烷异构化的反应机理。结果表明,正庚烷的异构化是双分子聚合裂化和经由金属环丁烷中间体的键转移机理协同作用的结果,异构产物以甲基己烷为主,同时产生部分二甲基戊烷和环烷烃以及裂化产物;在533～553K内,反应温度对正庚烷异构生成甲基己烷的影响不明显,但提高温度能促进裂化反应;氢气压强提高同时抑制异构化和加氢裂化反应;降低空速有利于单甲基己烷向辛烷值更高的二甲基戊烷转化;氢烃体积比增加对异构化反应有抑制作用,对裂化反应没有影响。

Molybdenum carbide supported on Hβ zeolite catalysts were prepared by the method of temperature programmed reduction used the n-pentane as a carburizing agent and characterized by XRD.Isomerization of n-heptane over the Hβ zeolite supported molybdenum carbide catalysts was carried out in a fixed bed.Effects of reaction parameters on the products distribution were investigated and the mechanism of n-heptane isomerization was discussed.The results show that isomerization of n-heptane is according to dimerization cracking mechanism and metal cyclobutane mechanism.Major isomerized products of n-heptane are methylhexanes.Simultaneously,dimethyl pentanes,cycloparaffins and some cracked products are produced.The reaction temperature do not influence the isomerization to methylhexane obviously in 533~553 K,but increased temperature can promote the cracking reaction.Arising of hydrogen pressure inhibit both isomerization and hydrocracking.Decreased space velocity is benefit to the conversion from methylhexanes to imethyl pentanes.The increasing hydrogen to hydrocarbon ratio inhibited isomerization,but had no effect on cracking reaction.