期刊
ACS CATALYSIS
卷 9, 期 4, 页码 2880-2892出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.8b04493
关键词
zeolite; hierarchical structure; Al distribution; methanol-to-olefin; hydrocarbon pool
资金
- Korea Research Institute of Chemical Technology [511801-06]
- National Research Foundation (NRF) - Ministry of Science and ICT, Republic of Korea [2017M1A2A2043133]
- National Research Foundation of Korea [2017M1A2A2043133] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Incorporating mesoporosity into zeolite catalysts has been regarded as an innovative technology that improves diffusivity and catalytic lifetime. Here, we propose a facile synthesis of the hierarchically structured ZSM-5 with accompanying intracrystalline mesopores, which was achieved by controlling the growth rate of the zeolite nanocrystals without using extra additives. As the crystallization temperature is strongly related to the formation of primary nanocrystals and their further growth, which fills gaps between those nanocrystals, the hierarchically structured ZSM-5 zeolite was synthesized at low crystallization temperatures (<140 degrees C). Al-27 MAS NMR and UV-vis-DRS analyses revealed that the hierarchically structured ZSM-5 prepared in the present study contained Al located in the straight channel at a higher proportion than the conventional microporous ZSM-5. The substitution of Al was calculated to be more difficult at the channel intersection than at other T-sites, supporting the experimental results. The hierarchically structured ZSM-5 exhibited excellent stability as well as selectivity for a methanol-to-olefin reaction. Reaction free energies calculated along the hydrocarbon pool mechanism pathway revealed that the Al located in the straight channel drives the reaction through the alkene-based cycle, which is responsible for the high olefin selectivity of the hierarchically structured ZSM-5.
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