Abstract
CO2 hydrogenation is an effective way to convert CO2 to value-added chemicals (e.g., CH4 and CH3OH). As a thermal catalytic process, it suffers from dissatisfactory catalytic performances (low conversion/selectivity and poor stability) and high energy input. By utilizing the dielectric barrier discharge (DBD) technology, the catalyst and plasma could generate a synergy, activating the whole process in a mild condition, and enhancing the conversion efficiency of CO2 and selectivity of targeted product. In this review, a comprehensive summary of the applications of DBD plasma in catalytic CO2 hydrogenation is provided in detail. Moreover, the state-of-the-art design of the reactor and optimization of reaction parameters are discussed. Furthermore, several mechanisms based on simulations and experiments are provided. In the end, the existing challenges of this hybrid system and corresponding solutions are proposed.
Highlights
With economic development, industrialization, and human activity, the continuous increasing emission of CO2 has led to the increase of global temperature which has an impact on the earth’s ecological environment, such as glacier melting and sea level rise [1,2]
While in the production of CH3OH, the combination of dielectric barrier discharge (DBD) plasma and CuO/ZnO/Al2O3, the optimal reaction temperature was lowered by 120 ◦C compared with the catalyst only approach [26]
To realize the low-temperature and efficient conversion of CO2 and high selectivity of targeted products via hydrogenation, the catalyst can be integrated with the DBD plasma reactor to generate a synergy, where the respective properties of active metals, supports, and promoters can be effectively combined
Summary
Industrialization, and human activity, the continuous increasing emission of CO2 has led to the increase of global temperature (i.e., global warming) which has an impact on the earth’s ecological environment, such as glacier melting and sea level rise [1,2]. The possible reaction mechanisms of various hydrogenations of CO2 are as below (Figure 1a,b) Based on their exothermic nature, these processes are thermodynamically favored at low temperatures; considering the eight-electron reduction of CO2 and activation of H2, a catalyst is necessary for the activation of CO2 and H2 to enhance the reaction kinetics [24]. Coupling with non-thermal plasma (NTP), especially dielectric barrier discharge (DBD)-generated plasma can form a synergy where both a mild reaction condition and high selectivity are achieved (Figure 1c). In the plasma–catalyst hybrid system, a high conversion efficiency and selectivity can be obtained at a relatively milder reaction condition. While in the production of CH3OH, the combination of DBD plasma and CuO/ZnO/Al2O3, the optimal reaction temperature was lowered by 120 ◦C compared with the catalyst only approach [26]. Two man-made plasmas are mainly involved in research, that is, completely ionized plasmas (fusion plasmas) and weakly ionized plasmas
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