Pt/HZSM-5催化剂上甲基环戊烷的临氢转化 Ⅰ.反应条件对扩环反应的影响

The effects of reaction parameters such as temperature, pressure, and hydrogen to hydrocarbon ratio (H2/HC) on the hydroconversion of methylcyclopentane (MCP) over Pt/HZSM-5 have been investigated in a fixedbed downflow reactor. The catalytic evaluation results were compared with the thermodynamic calculation data in order to investigate the behavior of MCP Ring enlargement (RE) reaction. Methylcyclopentane hydroconversion is described as a linear combination of three reactions: ring enlargement (RE), ring opening (RO) and cracking (CR), and RE reaction produces cyclohexane (CH) and benzene (Bz). It was shown that the conversion of MCP increased with the increase in temperature or with the decrease in H2/HC mol ratio, whereas decreased with the increase of pressure. The influence of the reaction parameters on the RE selectivity presented a complicated picture. With the increase in temperature, the RE selectivity first increased and then decreased, showing a maximum at a certain temperature. The effect of the H2/HC mol ratio was found to be relevant with temperature. At lower reaction temperatures, the RE selectivity decreased with decrease in the H2/HC mol ratio. However, at higher reaction temperatures, the H2/HC mol ratio had little influence on RE selectivity. The distribution of RE products between CH and Bz provides information on the reaction pathway. The experimental Bz/CH ratio was in excess of the equilibrium value, which strongly suggested that Bz, as the same as CH, could be a primary product from MCP. Thus, a modified reaction pathway of RE reaction could be proposed as follows: both CH and Bz were produced from the same intermediate, which was an adsorbed species on the dual function catalyst formed from MCP. In other words, the isomerization and dehydroisomerization are parallel reactions, producing CH and Bz, respectively. Meanwhile, Bz can come from CH through dehydrogenation.