Catalytic cracking of n-hexane for producing propylene on MCM-22 zeolites

• Published in: Applied catalysis. A, General Vol. 504; pp. 192 - 202
• Main Authors: Wang, Yong, Yokoi, Toshiyuki, Namba, Seitaro, Kondo, Junko N., Tatsumi, Takashi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05-09-2015
• Subjects: Catalytic cracking; Dealumination of H-MCM-22; Lewis acid site; Dealumination of H-MCM-22; Lewis acid site; Catalytic cracking
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2014.12.018

•The catalytic performance of MCM-22 zeolites in n-hexane cracking has been investigated at high n-hexane conversions.•The relationship between the catalytic performance and the acid properties has been investigated.•MCM-22 zeolites with higher Si/Al ratios exhibited better catalytic performance due to the lower amount and strength of acid sites.•Dealuminated MCM-22 zeolites by using ammonium hexaflurosilicate (AHFS) treatment showed the higher catalytic life and propylene selectivity at very high n-hexane conversions, due to the smaller amount of Lewis acid sites.
The catalytic cracking of n-hexane for producing propylene on MCM-22 catalysts was carried out as a model reaction of naphtha cracking. H-MCM-22 catalysts with different Si/Al ratios were prepared by direct or post-synthesis methods. The propylene selectivity was improved with an increase in the Si/Al ratio. Dealumination of H-MCM-22 with ammonium hexaflurosilicate (AHFS) (Del-Al-MCM-22) resulted in the increase in the catalytic life and propylene selectivity at a very high n-hexane conversion. This may be attributed to the decrease in the amount of Lewis acid sites which accelerate the hydride transfer and resultant coke formation. Del-Al-MCM-22 (Si/Al=62) catalyst showed a high propylene selectivity (40 C-%) which was higher than H-ZSM-5 and H-Beta catalysts with similar Si/Al ratios at a high n-hexane conversion of 95%. Moreover, it showed a catalytic life comparable with H-ZSM-5 and longer than H-Beta catalyst.