Atmospheric Pressure and Room Temperature Synthesis of Methanol through Plasma-Catalytic Hydrogenation of CO₂

Abstract

CO2 hydrogenation to methanol is a promising process for CO2 conversion and utilization. Despite a well-developed route for CO hydrogenation to methanol, the use of CO2 as a feedstock for methanol synthesis remains underexplored, and one of its major challenges is high reaction pressure (usually 30–300 atm). In this work, atmospheric pressure and room temperature (∼30 °C) synthesis of methanol from CO2 and H2 has been successfully achieved using a dielectric barrier discharge (DBD) with and without a catalyst. The methanol production was strongly dependent on the plasma reactor setup; the DBD reactor with a special water-electrode design showed the highest reaction performance in terms of the conversion of CO2 and methanol yield. The combination of the plasma with Cu/γ-Al2O3 or Pt/γ-Al2O3 catalyst significantly enhanced the CO2 conversion and methanol yield compared to the plasma hydrogenation of CO2 without a catalyst. The maximum methanol yield of 11.3% and methanol selectivity of 53.7% were achieved over the Cu/γ-Al2O3 catalyst with a CO2 conversion of 21.2% in the plasma process, while no reaction occurred at ambient conditions without using plasma. The possible reaction mechanisms in the plasma CO2 hydrogenation to CH3OH with and without a catalyst were proposed by combined means of electrical and optical diagnostics, product analysis, catalyst characterization, and plasma kinetic modeling. These results have successfully demonstrated that this unique plasma process offers a promising solution for lowering the kinetic barrier of catalytic CO2 hydrogenation to methanol instead of using traditional approaches (e.g., high reaction temperature and high-pressure process), and has great potential to deliver a step-change in future CO2 conversion and utilization.

A review on the recent progress, challenges, and perspectives of atmospheric‐pressure cold plasma for preparation of supported metal catalysts

“…It is composed by an approximately equal number of negative electrons (and negative ions sometimes) and positive ions, and ground‐state atoms and molecules, and excited atoms and molecules, and a strong electric field . Cold plasma, characterized by high electron temperature and low gas temperature (may be close to room temperature), has recently been widely adopted for decomposition, reduction, regeneration, and modification of catalysts …”

Hydrogenation of Carbon Dioxide to Value-Added Chemicals by Heterogeneous Catalysis and Plasma Catalysis

“…Recently, Wang et al examined the influence of plasma reactor structure and catalysts on CO 2 conversion and CH 3 OH selectivity for plasma catalytic CO 2 hydrogenation [125], and a schematic diagram of the experimental setup and images of the H 2/ CO 2 discharge are shown in Figure 22. They investigated three kinds of reactors, i.e., a cylindrical reactor (aluminum foil sheet as ground electrode), a double dielectric barrier discharge reactor (water as ground electrode), and a single dielectric barrier discharge reactor (water as a ground electrode).…”

“…All the above studies show a strong synergistic effect between plasma and catalysts. Images of H2/CO2 discharge generated in DBD reactor without catalyst, reprinted with permission from [125]. Copyright American Chemical Society, 2017.…”

“…(a) Schematic diagram of the experimental setup of a DBD plasma catalytic reactor. (b) Images of H 2/ CO 2 discharge generated in DBD reactor without catalyst, reprinted with permission from[125]. Copyright American Chemical Society, 2017.…”

Investigation of the Phase Equilibria of CO2/CH3OH/H2O and CO2/CH3OH/H2O/H2 Mixtures

“…The current research on the CH 3 OH synthesis covers a broad pressure range. The pressure varies from atmospheric pressure processes with the aid of a plasma [8], over mid-pressure (30-50 bar) processes [9][10][11][12][13][14] to high-pressure processes [15][16][17][18][19][20][21]. Mostly, heterogeneous catalysts based on copper, gold, or palladium are applied.…”