不同链长正构烷烃在Pt/SAPO-11催化剂上的临氢转化规律研究

采用SAPO-11分子筛制备的双功能催化剂,以碳链长度为10-14的正构烷烃为模型化合物,探索了不同碳数的长链正构烷烃临氢转化反应规律。结果表明,低温下不同碳数的正构烃都表现出较高的异构化选择性,改变反应温度使反应转化率控制在85%以下时,正构烷烃的异构化选择性可以达到90%左右;随着碳数和温度升高,正构烷烃由于发生明显的裂化反应导致转化率提高和异构化选择性降低。采用SAPO-11分子筛催化材料的双功能催化剂具有明显的产物择形异构效应,异构化产物以甲基位于端位和碳链中心的单侧链异构体为主,双(多)支链产物较少。长链正构烷烃在Pt/SAPO-11催化剂上的裂化反应在低转化率以加氢裂化为主,裂化产物的碳数呈均匀分布;在高转化率下以酸催化裂化为主,裂化产物的碳数分布呈现明显的不对称分布特征。

Study on the transformation rule of different long chain alkane hydroisomerization over Pt/SAPO-11 catalyst

The reaction mechanism of hydroisomerization of n-alkanes, from n-decane to n-tetrodecane, over Pt/SAPO-11 catalyst was studied. Results indicated that the n-alkanes with different carbon atom numbers exhibited higher isomerization selectivity at lower temperatures. The isomerization selectivity of n-alkanes can reach 90% by controlling temperature to keep the conversion rate lower than 85%. The conversion rate of n-alkanes was increased and the selectivity of isomerization was decreased with the increase of carbon atom number and temperature due to the occurrence of cracking reaction. Bifunctional catalyst has a good product shape selective effects. The isomerization products are mainly composed of unilateral chain isomers which have the methyl at the end and the center of the carbon chain. At low conversion rate, the cracking reaction of the long-chain n-alkanes over the Pt/SAPO-11 catalyst was mainly catalytic hydrocracking, the carbon number distribution of the cracking products was uniform. However, at high conversion rate, the reaction was mainly acid catalytic cracking, the carbon number distribution of cracking products was obvious asymmetric distribution.