Alkylation of benzene with carbon dioxide to low-carbon aromatic hydrocarbons over bifunctional Zn-Ti/HZSM-5 catalyst

Integration of Nano-Sized HZSM-5 with ZnZrOx as a Bifunctional Catalyst to Boost Benzene Alkylation with Carbon Dioxide and Hydrogen

“…Combined with the above results and literature reports, ,,,, the mechanism of benzene alkylation with CO 2 /H 2 could be proposed as follows (Figure ): CO 2 adsorbed on oxygen vacancies in ZnZrO x as carbonate and interacted with H species activated by ZnO, then hydrogenating into HCOO* and CH 3 O* species stepwise, which is consistent with the classic formate-methoxy pathway in CO 2 hydrogenation into the methanol reaction. By combining with HZSM-5, CH 3 O* species migrated, and operando were consumed by reacting with benzene through a Friedel–Crafts alkylation mechanism on the BASs in HZSM-5.…”

“…Therefore, it is of commercial and scientific interest to convert excessive benzene to valuable toluene or xylene through an alkylation reaction. Current approaches mainly focus on using methanol, − syngas, − methane, , or CO 2 − as the methylation reagents to react with benzene. Among these, CO 2 -coupled benzene alkylation is considered as a doubly beneficial route, which can not only increase the production of the high value-added toluene and xylene but also utilize CO 2 to alleviate the greenhouse effect …”

Thermodynamic and Mechanistic Analyses of Direct CO2 Methylation with Toluene to para-Xylene

“…One is the indirect methylation route including CO 2 hydrogenation to methanol , and subsequent methanol methylation with toluene, ,, where the metal oxide (MO X ) and modified zeolite are the catalysts for these two steps separately. The other one is the direct methylation route upon a bifunctional catalyst combining CO 2 hydrogenation and methylation as a tandem catalysis process. − Similarly, syngas (CO + H 2 ), as another C1 feedstock, has also been introduced in the direct methylation route, − while direct CO 2 methylation with benzene has also demonstrated to be more advantageous. , For direct CO 2 methylation, Zuo and Yuan et al concluded that the methoxy H 3 CO* species formed on MO X preferably migrate into the channel of zeolite for methylation with adsorbed toluene rather than desorb as methanol. Liu et al believed that the intermediate-generated methanol is the key species that consumed by benzene or toluene on the acid sites of zeolite.…”

“…The other one is the direct methylation route upon a bifunctional catalyst combining CO 2 hydrogenation and methylation as a tandem catalysis process. − Similarly, syngas (CO + H 2 ), as another C1 feedstock, has also been introduced in the direct methylation route, − while direct CO 2 methylation with benzene has also demonstrated to be more advantageous. , For direct CO 2 methylation, Zuo and Yuan et al concluded that the methoxy H 3 CO* species formed on MO X preferably migrate into the channel of zeolite for methylation with adsorbed toluene rather than desorb as methanol. Liu et al believed that the intermediate-generated methanol is the key species that consumed by benzene or toluene on the acid sites of zeolite. Due to the complex reaction pathways and various products of olefins, liquid fuel, and aromatics, ,, the tandem catalysis is the poor selectivity due to thermodynamic barrier and competitive side reactions.…”

Alkylbenzene synthesis from benzene and syngas over a ZnCrOx/beta bifunctional catalyst

“…Benzene conversion reached 34.7%, and the toluene and xylene selectivity were 68.8 and 18.0%, respectively. Liu 27 investigated the alkylation reaction of benzene with CO 2 and H 2 over a Zn0.1Ti-ZSM-5(13.5) hybrid catalyst. The conversion of benzene and CO 2 could reach 28.7 and 29.9%, respectively, by adjusting the oxygen vacancies in Zn/Ti and the ZSM-5 acidity of the catalyst.…”