Project Leader: Prof. Xiulian Pan
Supported by Natural Science Foundation of China(Major Research Plan)
Project Number: 91945302
Abstract:
Light olefins (ethylene, propylene and butene) are important basic chemicals in chemical industry. Direct synthesis of light olefins from syngas remains a hallenge for C1 chemistry because of its selectivity. Under the support of NSFC, this project focuses on syngas-to-light olefins conversion OXZEO®-TO process, which was originally proposed in China. The project has collected ultidisciplinary researchers and focuses on catalyst development, in situ characterization and theoretical calculations with the research focus on the fundamental understanding of the catalytic mechanism in order to further optimize the catalyst and the catalytic process. After two-years study, we have made progress in the following aspects: 1. Regarding applied research, the catalyst preparation has been upscaled to the scale of ton. The pilot plant test with a scale of thousand ton/year has also been successfully completed. 2. Regarding fundamental research, by combining experimental and theoretical studies, we have gained deeper insights to the reaction mechanism. For instance, (1) the activity and product selectivity of metal oxides increases with the reducibility. A higher reducibility leads to a higher activity. A less reduced ZnO mainly leads to methane formation and a highly reduced ZnO surface mainly gives ketene whereas over-reduced surface facilitates formation of methane. It is similar for ZnCr2O4: a higher reduced ZnCr2O4 surface benefits activation of syngas, favors C-O breaking rather than hydrogenation of CO. Thus the reaction goes along the pathway of ketene. A less reduced surface favors CO hydrogenation than C-O breaking and thus CH3OH selectivity is higher. (2) Zeolite catalyzes the C-C coupling of intermediates. Thus CH2CO decomposition is hindered and therefore shifts the reaction towards olefins formation. However the acidity of zeolite also catalyses the secondary reaction of ethylene, leading to reduced selectivity. Therefore, both the topology and acidity of zeolites play an important role in syngas conversion. (3) Proximity of metal oxides and zeolites, generally a closer proximity benefits the CO conversion and light olefin selectivity. However, for metal oxides such as Zn-based oxides, which may migrate under reaction conditions, there exists an optimum proximity. In comparison, for metal oxides, such as MnOx, which do not contain migration species, the light olefin selectivity benefits from closer proximity. These fundamental understandings lay down an important basis to form and improve the concept of OXZEO®, which is not only important for CO but also for CO2 hydrogenation to synthesize a series of highly value-added chemicals. Furthermore, highly active catalyst has thus been prepared, which achieves 60% CO conversion and >70% light olefin selectivity.
Key Words:
syngas conversion; light olefins; OXZEO; selectivity control; surface chemistry
Publications:
1. Oxide-Zeolite-Based Composite Catalyst Concept That Enables Syngas Chemistry beyond Fischer-Tropsch Synthesis
Xiulian Pan*, Feng Jiao, Dengyun Miao, Xinhe Bao*
Chemical Reviews, 121(2021)(11)6588-6609
2. Effects of Proximity-Dependent Metal Migration on Bifunctional Composites Catalyzed Syngas to Olefins
Yi Ding, Feng Jiao, Xiulian Pan*, Yi Ji, Mingrun Li, Rui Si, Yang Pan, Guangjin Hou, Xinhe Bao*
ACS Catalysis, 11(2021)(15)9729-9737
3. Role of SAPO-18 Acidity in Direct Syngas Conversion to Light Olefins
Gen Li, Feng Jiao*, Xiulian Pan*, Na Li, Dengyun Miao, Lin Li, Xinhe Bao
ACS Catalysis, 10(2020)12370-12375
4. Selective Synthesis of Benzene, Toluene, and Xylenes from Syngas
Dengyun Miao, Yi Ding, Tie Yu, Jian Li, Xiulian Pan*, Xinhe Bao*
ACS Catalysis, 10(2020)(13)7389-7397
5. C-C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM-5 Zeolite
Yuxiang Chen, Ke Gong, Feng Jiao, Xiulian Pan*, Guangjin Hou, Rui Si, Xinhe Bao*
Angewandte Chemie-International Edition, 59(2020)(16)6529-6534