Journal
JOURNAL OF CATALYSIS
Volume 394, Issue -, Pages 181-192Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcat.2020.08.020
Keywords
Syngas; Lower olefins; Mesoporous SAPO-34; Bifunctional catalysis; Reaction coupling; Methanol conversion; Zeolite deactivation; Shape catalysis
Categories
Funding
- National Key Research and Development Program of the Ministry of Science and Technology [2017YFB0602201, 2019YFE0104400]
- National Natural Science Foundation of China [91945301, 21673188, 21872112, 91545203]
- Shaanxi Coal and Chemical Technology Institute Co
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The integration of methanol synthesis and methanol-to-olefins conversion in a bifunctional process provides a new synthetic strategy for lower olefins. Designing matchable zeolite components remains challenging, but a hierarchical SAPO-34 zeolite with a sandglass-like structure shows promise in enhancing selectivity and stability in syngas conversion. High-pressure hydrogen and moderate density of acid sites play crucial roles in achieving high C-2-C-4(=) selectivity in the conversion process.
Bifunctional process integrating methanol synthesis and methanol-to-olefins conversion provides a new synthetic strategy for lower olefins (C-2-C-4(=)), whereas designing matchable zeolite components is still challenging due to the harsh reaction conditions. Here, a hierarchical SAPO-34 zeolite with a sandglass-like hollow structure is synthesized from an aluminum-rich precursor gel, which provides an abundance of crystal defects during zeolite crystallization. The bifunctional catalyst obtained by integrating the hierarchical SAPO-34 and ZnO-ZrO2 oxide offers a C-2-C-4(=) selectivity of 80% at 25% CO conversion with excellent stability in syngas conversion. We demonstrate that in the presence of high-pressure hydrogen, a moderate density of acid sites is the prerequisite for obtaining high C-2-C-4(=) selectivity in syngas/methanol conversion, because the olefins are easily hydrogenated into alkanes by excessive Bronsted acid sites. The hierarchical architecture significantly prolongs the lifetime of bifunctional catalysts, by facilitating C-2-C-4(=) desorption and slowing down the coking rate. (c) 2020 Elsevier Inc. All rights reserved.
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