CO₂and CH₄are not only greenhouse gases but also important C1 resources, which are mainly converted to syngas via dry reforming. However, the high temperature (>800°C) is required due to the high thermodynamic stability of CO₂and CH₄. Methyl halide can be transformed into high-value chemicals under mild conditions, significantly reducing the difficulty of CH₄conversion. Moreover, introducing hydrogen-deficient (e.g. CO₂) into the hydrogen-rich chloromethane conversion system can effectively adjust the C/H balance between reactants and products. Nevertheless, whether CO₂can directly incorporate into target product remains a critical issue to be addressed in this process.

Recently, a research team led by Prof. LIU Zhongmin and Prof. ZHU Wenliang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) developed a high carbon utilization for CO₂conversion with chloromethane to aromatics using acidic zeolites as the catalyst.

High carbon utilization for CO₂conversion with chloromethane to aromatics over acidic zeolite catalyst (Image by FANG Xudong)

The researchers developed a high carbon utilization for CO₂conversion with chloromethane to aromatics using acidic zeolites as catalysts. They first demonstrated that introducing CO₂into CH₃Cl system not only promoted the conversion of chloromethane but also enhance aromatics formation, particularly benzene, toluene, and xylene (BTX). Specifically, the high aromatic selectivity and BTX selectivity reaching 71% and 50% could be obtained over H-ZSM-5 under 3.0 MPa and 450°C.

Through in-situ infrared spectroscopy, isotope tracing, and other characterization techniques, they discussed the reaction mechanism and demonstrated the direct involvement of CO₂in the formation of aromatics. Furthermore, by capturing key intermediates, they confirmed that lactone, cyclopentenone, and cycloalkenes are crucial intermediate species in the coupled conversion of chloromethane and CO₂, and proposed the coupling reaction mechanism.

“Our study would provide a new approach for the large-scale and high-value utilization of methane and CO₂, with promising prospects.”

The study was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of CAS, the Dalian High-Level Talent Innovation Support Program, and National Special Support Program for High-Level Talents. (Text by FANG Xudong and LIU Hongchao)

Key words:CO₂utilization; CH₄conversion; CH₃Cl; Aromatics; Lactone; Acidic zeolites;

High carbon utilization for CO₂conversion with chloromethane to aromatics over acidic zeolite catalyst. Xudong Fang, Bin Li, Hongchao Liu*, Mingguan Xie, Zhiyang Chen, Leilei Yang, Jingfeng Han, Wenliang Zhu*, Zhongmin Liu, Chem Catalysis, 2023.