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采用脉冲微反装置评价了纯正丁烷、含有不同比例异丁烷的混合丁烷在Au改性的纳米HZSM-5催化剂上的反应活性和异构化选择性。结果表明,在300℃时,载金量为1.31%的催化剂上纯正丁烷原料的转化率可达7.0%,异丁烷选择性可达80%以上。相比之下,在纳米HZSM-5载体上正丁烷的转化率只有0.55%,异丁烷选择性仅为11.67%。在Au负载量为0.12%~1.91%,随着Au负载量的增加,正丁烷转化率先增后减,异丁烷选择性在低负载量时增加明显。在反应温度低于400℃时,纯正丁烷在载金催化剂上主要发生异构化反应;高于400℃时,主要发生裂解和芳构化等反应,即400℃是正丁烷在脉冲微反条件下异构化和裂解等反应的分水岭。另外,混合丁烷的组成对正丁烷异构化反应有一定影响,但在适当温度下正丁烷异构化时裂解产物很少,表现出金属-酸双功能催化特征。Au+在反应中发挥了脱氢和加氢作用。
The reactivity and isomerization selectivity of pure butane, mixed butane containing different proportions of isobutane on the Au-modified nano-HZSM-5 catalyst were evaluated by pulse microreactor. The results show that at 300 ℃, the conversion of pure butane raw material can reach 7.0% and the selectivity of isobutane can reach more than 80%. In contrast, the N-HZSM-5 support has a conversion of n-butane of only 0.55% and an isobutane selectivity of only 11.67%. With the Au loading of 0.12% ~ 1.91%, the n-butane conversion increases first and then decreases with the increase of the Au loading, and the selectivity of isobutane increases obviously at low loading. When the reaction temperature is lower than 400 ℃, pure butane mainly undergoes isomerization reaction on the supported catalyst. When the temperature is higher than 400 ℃, cracking and aromatization reaction occur mainly. That is, Under the conditions of isomerization and cracking reaction watershed. In addition, the composition of mixed butane has an effect on the isomerization of n-butane, but the isomerization of n-butane at the proper temperature has very few pyrolysis products and shows the catalytic characteristic of metal-acid bifunctional catalysis. Au + plays a role of dehydrogenation and hydrogenation in the reaction.