Examination of key factors determining the catalytic performance of Zn-Ga/HZSM-5 bifunctional catalysts and establishment of reaction network in alkylation of benzene with carbon dioxide

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

“…As shown in Figure 12a, in the presence of benzene, the peaks of soluble coke species were relatively low and mainly consisted of toluene, xylene, dimethyl-benzaldehyde, and a few oxygenated aromatics. However, as for CO 2 /H 2 without benzene feed-in, all the peaks elevated significantly compared with the other two samples 15 because of the self-reaction of CH 3 O*/ methanol initiated by the double-cycle mechanism 63,64 or triple-cycle mechanism, 26,31,57,65 in which the hydrocarbon pool played an important role in the cycle, and the more C 4+ and C 9+ species in liquid product (Figure S7) also confirmed the existence of more alkene pool and aromatic pool spices. Due to the rapid consumption of CH 3 O* by benzene alkylation reaction, the methanol self-reaction was suppressed, and the formation of hydrocarbon pool species was also restrained, resulting in a more concentrated production distribution in benzene alkylation with CO 2 /H 2 .…”

“…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 …”

“…Tandem catalysis processes typically require relatively high temperatures to promote C–C coupling reactions, where the reversed water gas shift (RWGS) reaction becomes the main side reaction. By tuning the oxygen vacancies of the oxide, the conversion and usage of CO 2 could be improved, and the selectivity of CO could be suppressed. − ,, Due to the rich adjustable acidic sites, suitable microporous structure, and unique shape selectivity, HZSM-5 has been widely used as a zeolite component in OXZEO catalysts for benzene alkylation with CO 2 /H 2 . By tuning the acid properties of HZSM-5, the product distribution toward xylene/toluene and catalyst stability could be optimized.…”

Identifying the Location of Real Active Sites in ZSM-5 Zeolites for Tetralin Conversion into Light Aromatics

“…Light cycle oil (LCO), as the main byproduct in fluid catalytic cracking processes, is majorly composed of condensed aromatics (>75%), most of which are bi- or tricyclic homologues such as naphthalene, alkylnaphthalene, anthracene, and phenanthrene. − LCO used to be added into diesel oil for viscosity adjustment; however, for diesel upgrading, this demand has witnessed a steep decrease during the last decade owing to its drawbacks like the low cetane number and poor ignition performance. , Meanwhile, light aromatics such as benzene, toluene, and xylene (BTX) are important raw materials in the chemical market, and demand will continue to increase in the future . For example, the worldwide increasing demand in paraxylene (PX) will maintain a growth of 3.5% over the next 5 years as a result of its importance as a major chemical in producing plastics and synthetic fibers. − At the same time, due to the growing demand for downstream products, the growth in demand for BTX is much more than that for refined oil. , The high content of potential aromatics in LCO makes it a possible source for the production of light aromatics. As a result, the techniques to convert LCO into BTX have gradually become a hot research field.…”

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.…”