基于脉冲微反装置的Au/HZSM-5催化剂上正丁烷反应性能研究

以HZSM-5沸石分子筛为载体,尿素为沉淀剂,采用常压沉积-沉淀法和负压沉积-沉淀法制备了系列Au/HZSM-5沸石催化剂并采用常规催化剂表征方法对其进行了表征.用脉冲微反装置评价了纯正丁烷(99.9%)在氢型和金改性的纳米HZSM-5催化剂上的反应活性和烯烃选择性.结果表明,在550℃下,负压沉积-沉淀法制备的不同金负载量的纳米HZSM-5催化剂上的转化率和烯烃选择性都远高于常压沉积沉淀法制备的催化剂.改性量为2.0%的Au/HZSM-5-A(负压)催化剂正丁烷转化率达到了58.0%、烯烃选择性为57.2%.脱氢和脱甲基活化是正丁烷的重要活化方式,也是影响其烯烃选择性的主要因素.金改性在提高正丁烷转化率的同时,也促进了正丁烷的脱氢和脱甲基活化.纳米HZSM-5因晶粒度小,孔道短和微孔扩散阻力低而有利于正丁烷转化.负压有利于清除HZSM-5内部的无定型杂质和脱气净化处理,有利于金的负载量和分散度.

The Performance of Au/HZSM-5 Catalysts for the Conversion of n-butane Based on Mini-scale Pulse Reactor

Atmospheric pressure deposition-precipitation (APDP) and negative pressure deposition-precipitation (NPDP) methods were used to prepare Au/HZSM-5 catalysts using HZSM-5 as carrier and urea as precipitant. The performance of the catalysts for converting n-butane was evaluated by a micro-scale pulse reactor. The results showed that the conversion and selectivity of n-butane to olefins of the reaction catalyzed by 2.0% (wt) Au/HZSM-5 prepared by NPDP method were respectively as high as 58.0% and 57.2%, which were much higher than those catalyzed by Au/HZSM-5 prepared by APDP. It was because that the degasification and removal of the amorphous impurities from HZSM-5 during the catalyst preparation were promoted under negative pressure, and then the loading amount and dispersion of Au on HZSM-5 were increased. Additionally, it was found the dehydrogenation and demethylation reactions, which were the main reactions for conversion and selectivity promotion of n-butane, were promoted by Au. The nano-sized HZSM-5, having short pore, could reduce the diffusion resistance during the catalyst preparation and n-butane conversion processes.