Direct and Oriented Conversion of CO₂ into Value‐Added Aromatics

Abstract

The oriented conversion of CO2 into target high‐value chemicals is an effective way to reduce carbon emissions, but still presents a challenge. In this communication, we report the oriented conversion of CO2 into value‐added aromatics, especially para‐xylene, in a single pass by combining core–shell structured Zn‐doped H‐ZSM‐5 (Zn‐ZSM‐5@SiO2) and a Cr2O3 component. Through precise regulation of the acidity of Zn‐ZSM‐5@SiO2, high para‐xylene selectivity (38.7 % in the total products) at a CO2 conversion of 22.1 % was achieved. Furthermore, a CO2‐assisted effect in the synthesis of aromatics during the tandem process has been clarified through a control experiment. The CO2 reactant can act as a hydrogen acceptor to accelerate the dehydrogenation of alkenes, intermediates in the synthesis of aromatics, thereby increasing the driving force towards aromatics in the tandem reaction process.

Selective methylation of toluene using CO 2 and H 2 to para -xylene

“…In tandem catalysts composed of oxides and zeolites, intermediates can migrate between the two components ( 19 – 24 ). Hydrogenation of CO 2 or CO can also directly produce aromatics ( 14 – 16 , 22 , 25 , 26 ), but the production distribution is complex and the selectivity to xylene is usually less than 30%. On the basis of the cognizance above, CO 2 and H 2 are introduced as methylation reagents into toluene methylation reaction over ZZO-Z5 dual-functional catalysts.…”

A Well‐Defined Core–Shell‐Structured Capsule Catalyst for Direct Conversion of CO2 into Liquefied Petroleum Gas

“…The numbers of Lewis acid sites and Brønsted acid sites of the Pd/SiO 2 –SZ catalyst were measured by pyridine adsorption infrared spectroscopy (Py‐IR; Figure S8 and Table S2). Two bands were observed at approximately 1455 and 1545 cm −1 , corresponding to Lewis acid sites and Brønsted acid sites, with acidic strengths of 44.4 and 19.2 μmol g −1 , respectively. The higher Lewis/Brønsted acid ratio is beneficial for the methanol to aromatics (MTA) conversion process.…”

Selective Conversion of CO2 into para‐Xylene over a ZnCr2O4‐ZSM‐5 Catalyst

“…In the traditional methanol‐to‐aromatics (MTA) reaction, ZSM‐5 zeolite shows excellent performance for PX selectivity, owing to the suitable microporous channel size for the PX product diffusion (shape selectivity) [9] . In theory, PX and other light aromatics (benzene, toluene, and other xylenes) are formed over the internal acid sites of the micropores on ZSM‐5 zeolite, which are subsequently alkylated to heavy aromatics or isomerized to other xylenes, due to the external surface acidity and the thermodynamics effect [10] . In order to enhance PX selectivity, it is vital to eliminate the external acidity of ZSM‐5 zeolite.…”