Effect of alkali metal cations modification on the acid/basic properties and catalytic activity of ZSM-5 in cracking of supercritical n-dodecane

作     者：Ji, Yajun Yang, Honghui Yan, Wei 

作者机构：Xi An Jiao Tong Univ Dept Environm Sci & Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China 

出 版 物：《FUEL》 (燃料)

年 卷 期：2019年第243卷

页      面：155-161页

核心收录：

学科分类：0820[工学-石油与天然气工程] 080702[工学-热能工程] 0817[工学-化学工程与技术] 08[工学] 0807[工学-动力工程及工程热物理] 

基　　金：National Natural Science Foundation of China Key R&D Programs in Shaanxi Province [2018SF-372] 

主　　题：ZSM-5 Alkali metal Acid property Catalytic cracking Coke Heat sink 

摘      要：Alkali metal modified ZSM-5 (ZSM-5-M, M: Li, Na, K, Cs) was prepared by ion-exchange method. The ion-exchange of alkali metal cations with silanol group occurred along with hydrolysis of the Si-O(H)-Al, leading to increase of Lewis acid, decrease of strong and Bronsted acids. K+ and Cs+ were easier to exchange with proton of -OH compared with Na+ and Li+ due to their smaller hydrated radius, resulting in higher ion exchange capacity for ZSM-5-K and ZSM-5-Cs. Their catalytic performances in supercritical n-dodecane cracking were studied. The gas generation rates (GGR) and heat sinks under 550 degrees C and 4 MPa increased as following: ZSM-5-Cs ZSM-5 ZSM-5-K ZSM-5-Li ZSM-5-Na. The GGR and heat sink of ZSM-5-Na reached 60.3% and 2826 kJ kg(-1), respectively. Thus moderate attenuation of strong acid and enhancement of basic sites could enhance the catalytic performance in supercritical n-dodecane cracking. The selectivity for light alkene was enhanced and the coke was restrained due to the regulated acid-base properties, since decreasing strong acidic sites and increasing the basic sites could suppress the secondary reactions that consumed light alkene and generated coke.