posted on 2023-12-15, 15:00authored byShujia Guo, Sheng Fan, Han Wang, Sen Wang, Zhangfeng Qin, Mei Dong, Weibin Fan, Jianguo Wang
Selective
conversion of CO2 into a specific hydrocarbon
is highly desirable but rather challenging. Herein, a bifunctional
ZnCrOx/H-ZSM-5 composite catalyst was
designed, which can selectively convert CO2 into trimethylbenzene
(TriMB) and ethene by hydrogenation. The selectivities to aromatics
and light olefins reach 64.6 and 26.1%, respectively, at a CO2 conversion of 17.5%. In particular, TriMB accounts for 57.4%
of the aromatic products, while ethene takes up 83.9% of all light
olefins. Various characterization and DFT calculation results reveal
that the CO2 conversion keeps to the tandem methanol-mediated
reaction route, viz., CO2 is first hydrogenated to methanol-related
intermediates over the ZnCrOx moiety and
the H-ZSM-5 moiety then carries on the further conversion of emerged
intermediates to hydrocarbons via the hydrocarbon pool mechanism.
The 10-ring channels of the ZSM-5 framework combined with an appropriate
quantity and distribution of acid sites conduce to the formation of
TriMB and meanwhile inhibit the C9-aromatics from further
methylation; in addition, compared with propene and butene, ethene
survives well from further evolution due to the higher energy barriers
for ethene methylation and dimerization. All of these endue the ZnCrOx/H-ZSM-5 composite catalyst with a high selectivity
to TriMB and ethene in the CO2 hydrogenation. The insight
shown in this work may give valuable clues for the design of efficient
catalysts in the conversion of CO2 to a specific hydrocarbon
product.