ABSTRACT
Even though the transformation of syngas into aromatics has been realized via a methanol-mediated tandem process, the low product yield is still the bottleneck, limiting the industrial application of this technology. Herein, a tailor-made zeolite capsule catalyst with Ga doping and SiO2 coating was combined with the methanol synthesis catalyst Cr2O3 to boost the synthesis of value-added aromatics, especially para-xylene, from syngas. Multiple characterization studies, control experiments, and density functional theory (DFT) calculation results clarified that Ga doped zeolites with strong CO adsorption capability facilitated the transformation of the reaction intermediate methanol by optimizing the first C-C coupling step under a high-pressure CO atmosphere, thereby driving the reaction forward for aromatics synthesis. This work not only reveals the synergistic catalytic network in the tandem process but also sheds new light on principles for the rational design of a catalyst in terms of oriented conversion of syngas.
ABSTRACT
Cu/ZnO catalysts with varied Cu/(Cu + Zn) molar ratios were prepared by a facile solid-state method. The Cu/(Cu + Zn) molar ratio displayed a significant effect on the oxygen vacancy formation of the calcined catalysts, thereby influencing the CuO-ZnO interaction and the reducibility of CuO. The Cu/(Cu + Zn) molar ratio also exhibited a significant effect on Cu0 surface area, oxygen vacancy, the ratio of ZnO(002) plane to ZnO(100) plane, as well as the basicity and acidity of the reduced catalysts, thereby affecting the catalytic performance for low-temperature methanol synthesis from syngas containing CO2. The correlations of methanol space time yield (STY) versus the physicochemical characteristics of Cu/ZnO catalysts were studied. The catalyst with equal amounts of Cu and Zn displayed the best catalytic activity owing to higher Cu0 surface area, more oxygen vacancy and ZnO(002) plane, as well as more moderately basic sites.
