【摘要】 在固定床反应器中研究了乙醇脱水反应中亚微米ZSM-5分子筛催化剂上乙醇、乙醚和乙烯的反应及积碳行为,采用TG、低温氮气吸附-脱附、吡啶吸附红外光谱和~13C NMR等方法对催化剂进行了表征,以考察分子筛催化剂的积碳行为及乙醇脱水反应机理。实验结果表明,乙醚是乙醇脱水生成乙烯的中间体,而乙烯低聚是积碳的主要来源;积碳的主要组成可能是烷基芳烃,而积碳速率与反应混合物中的烯烃含量及水含量有关,ZSM-5分子筛催化剂上各物质积碳速率由快到慢的顺序:乙烯>乙烯+水>乙醚>乙醇;在线反应100 h后,积碳堵塞了70%以上的催化剂孔道,并且消耗了80%以上的催化剂酸中心,因而导致催化剂活件有所降低。更多还原

【Abstract】 Reactions and coking behaviors of ethanol,diethyl ether or ethylene on a submicron ZSM-5 zeolite catalyst,which was used in dehydration of ethanol to ethylene,were studied in a fixbed reactor.The coking behavior and the dehydration mechanism were analyzed by means of TG,N₂ adsorption-desorption techniques,pyridine adsorption FTIR and ¹³C NMR.Experimental results showed that diethyl ether was an intermediate of the ethanol dehydration to ethylene and that ethylene oligomerization was responsible for the coke formation.The coke might consist mainly of alkyl aromatics and the coke deposition rate was correlated to the olefin content and the water content in the reaction mixture.The coke deposition rate on the ZSM-5 zeolite catalyst lowered in the following order;ethylene>ethylene and water>diethyl ether>ethanol,which were used as feeds separately. After 100 h on stream,the coke deposits blocked more than 70%of the catalyst pores,and consumed more than 80%of acid sites on the catalyst,which caused a loss of catalyst activity.更多还原