ZSM-5分子筛的碳四裂解性能及积碳研究

Catalytic Cracking of C_4 Olefins over ZSM-5 Zeolites and the Carbon Deposition

以1,6-己二胺为模板剂,在水热体系中合成了不同硅铝比的ZSM-5分子筛,考察了该系列分子筛的碳四烯烃裂解反应性能。实验结果表明,与低硅铝比的ZSM-5分子筛相比,高硅铝比的ZSM-5分子筛具有更高的稳定性及丙烯选择性,是更适合碳四烯烃裂解制丙烯的催化剂。采用13C CP-MAS NMR、Raman光谱、DTG和元素分析等多种表征手段对ZSM-5分子筛的积碳进行了研究。表征结果显示,ZSM-5分子筛中积碳量以及积碳类型均随反应时间的延长而发生明显的变化,积碳量随反应时间的延长而增加;积碳类型初期主要以脂肪族碳氢化合物为主,随反应的进行,积碳类型向芳香族碳氢化合物及类石墨型积碳转变。

ZSM-5 zeolites with different silica-alumina ratio were synthesized by a hydrothermal method in the Na2O-SiO2-Al2O3-H2N(CH2)6NH2 system and the catalytic cracking of C4olefins over the ZSM-5 catalysts were investigated. ZSM-5 zeolites with high silica-alumina ratio exhibited higher stability and propylene selectivity than those of ZSM-5 zeolites with low silica-alumina ratio. Carbon deposition on the ZSM-5 samples was studied by means of 13C CP-MAS NMR,Raman,DTG and element analysis. The results revealed that with prolonging the reaction time,the carbon deposition increased and the coke species changed from aliphatic hydrocarbons to aromatic and graphite hydrocarbons gradually.