Maximizing sinusoidal channels of HZSM-5 for high shape-selectivity to p-xylene

• Published in: Nature communications 2019-09, Vol.10 (1), p.4348-8, Article 4348
• Main Authors: Wang, Chuanfu, Zhang, Lei, Huang, Xin, Zhu, Yufei, Li, Gang (Kevin), Gu, Qinfen, Chen, Jingyun, Ma, Linge, Li, Xiujie, He, Qihua, Xu, Junbo, Sun, Qi, Song, Chuqiao, Peng, Mi, Sun, Junliang, Ma, Ding
• Format: Article
• Language: English
• Subjects: 140/131; 140/146; 147/135; 147/143; 639/166/898; 639/638/77/884; 639/638/77/887; Alkylation; Catalysis; Chemical industry; Chemical separation; Humanities and Social Sciences; Methylation; multidisciplinary; Organic chemistry; p-Xylene; Science; Science (multidisciplinary); Selectivity; Stability; Straight channels; Toluene; Xylene; Zeolites
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-12285-4

The shape-selective catalysis enabled by zeolite micropore’s molecular-sized sieving is an efficient way to reduce the cost of chemical separation in the chemical industry. Although well studied since its discovery, HZSM-5′s shape-selective capability has never been fully exploited due to the co-existence of its different-sized straight channels and sinusoidal channels, which makes the shape-selective p -xylene production from toluene alkylation with the least m -xylene and o -xylene continue to be one of the few industrial challenges in the chemical industry. Rather than modifications which promote zeolite shape-selectivity at the cost of stability and reactivity loss, here inverse Al zoned HZSM-5 with sinusoidal channels predominantly opened to their external surfaces is constructed to maximize the shape-selectivity of HZSM-5 sinusoidal channels and reach > 99 % p -xylene selectivity, while keeping a very high activity and good stability ( > 220 h) in toluene methylation reactions. The strategy shows good prospects for shape-selective control of molecules with tiny differences in size. Full utilization of ZSM-5 shape-selectivity is restricted by crystal external surface acid sites and co-existence of two different sized channels. Here, the authors synthesize reverse Al zoned ZSM-5 with sinusoidal channel preferentially opened to its inert external surface to achieve 99.3% p -xylene selectivity.