Effects of Dealumination and Desilication of Beta Zeolite on Catalytic Performance in n-Hexane Cracking

Catalysts

Yong Wang²  Toshiyuki Yokoi¹  Seitaro Namba²  Takashi Tatsumi² 

[1] Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan

关键词: n-hexane cracking;    propylene;    beta zeolite;    dealumination;    desilication;    Lewis acid sites;    mesopores;   

DOI  :  10.3390/catal6010008

来源: mdpi

【 摘 要 】

Catalytic cracking of n-hexane to selectively produce propylene on Beta zeolite was carried out. The H-Beta (HB) (Si/Al = 77) zeolite showed higher catalytic stability and propylene selectivity than the Al-rich HB (Si/Al = 12), due to its smaller number of acid sites, especially Lewis acid sites (LAS). However, catalytic stability and propylene selectivity in high n-hexane conversions were still not satisfactory. After dealumination with HNO₃ treatment, catalytic stability was improved and propylene selectivity during high n-hexane conversions was increased. On the other hand, catalytic stability was not improved after desilication with NaOH treatment, although mesopores were formed. This may be related to the partially destroyed structure. However, propylene selectivity in high n-hexane conversions was increased after alkali treatment. We successfully found that the catalytic stability was improved and the propylene selectivity in high n-hexane conversions was further increased after the NaOH treatment followed by HNO₃ treatment. This is due to the decrease in the number of acid sites and the increase in mesopores which are beneficial to the diffusion of coke precursor.

【 授权许可】

CC BY   
© 2016 by the authors; licensee MDPI, Basel, Switzerland.