Study On Carbon Dioxide Hydrogenation Conversion Using Cold Plasma Reaction Under Radio-Frequency (RF) Discharge

Carbon dioxide, the terminational oxidation product of carbon andcarbon—compounds, was significant in the comprehensive utilization of carbonresources and the control of environmental pollution. Plasma chemical reaction is animportant technology in modern chemical field. Radio frequency plasma is a kind ofnon-equilibrium cold plasma. In this paper, reactions of carbon dioxide conversionusing radio frequency plasma have been studied, in order to explore the efficientconversion of CO2.First of all, pure CO2 as objects, its conversion characteristics and law areinvestigated under RF plasma excitation conditions; secondly, H2 as appending gas, RFplasma activating conversion of CO2 hydrogenation is systematically studied in theabsence of catalyst and the presence of catalyst; CH4 as appending gas, orthogonalexperiment is used to analyze factors effecting conversion of CO2/CH4 reacting system.According to experiment data, the energy efficiency of plasma catalytic CO2 conversionreaction is explored, and activation and translation mechanism of CO2 are analysedunder various mode conversion.The results are summarized as follows:①Pure carbon dioxide could be mainly converted into carbon monoxide andoxygen under RF discharge plasma. Reaction of CO2 was primarily influenced bydischarge voltage, flux of CO2 and discharge area. Suitable reaction conditions: CO2flux of 180ml?min-1, discharge voltage of 900V, discharge area of 17.9608cm2, CO2conversion was up to 70.65%.②Under hydrogen plasma, the conversion of carbon dioxide was raised greatly.Carbon dioxide, carbon monoxide, methanol and methane were the main products. Theresults showed that: conversion of CO2 hydrogenation, yield and selectivity of productswere primarily influenced by four factors—discharge voltage, CO2/H2 ratio, total gasflow and discharge area. Feasible reaction conditions: total gas flow of 180ml?min-1,discharge voltage of 1000V, discharge area of 17.9608cm2, CO2/H2 ratio of 1:3, CO2conversion was up to 85.27%; methanol selectivity and yield were 6.73% and 5.74%respectively; methane selectivity 4.38%, and yield 3.73%.③synergistic effect of RF discharge plasma and catalyst on CO2/H2 system,carbon monoxide, carbon dioxide, methanol and methane were the main products, in addition, little water. Conversion of CO2 hydrogenation was primarily influenced byfour factors: discharge voltage, CO2/H2 ratio, total gas flow and discharge area, whileyield and selectivity of products (methanol and methane) were not only affected by thefour factors, but also deeply influenced by catalysts. Suitable reaction conditions: totalgas flow of 180 ml?min-1, discharge voltage of 1000V, discharge area of 7.0336cm2,CO2/H2 ratio of 1:9, CO2 conversion was up to 92.50%; when using copper-basedcatalyst, methanol selectivity and yield were 8.98% and 8.27% respectively; methaneselectivity 5.53%, and yield 5.09%.④Orthogonal experiment ( L16(44) ) was designed to optimize CO2/CH4 reaction.The feasible reaction conditions: discharge voltage 1000V, CO2/CH4 ratio 6, total fluxof 360ml?min-1, discharge area of 14.3184cm2. At this point, conversion of CO2 was94.67%; conversion of methane was 62.16%; the main products-C2 hydrocarbons hadbetter selectivity and yield, 32.89% and 25.70% respectively.⑤The action mechanism in the reaction system of plasma and catalyst is that: theplasma could activate reactants, while the catalyst could selectively improve yield.⑥Effective energy efficiency of CO2 could be increased by adjusting injectionpower, reactant ratio, total gas flow et al.