Conversion Of Greenhouse Gases By DBD Plasma-assisted G-C₃N₄-based Catalyst

As one of most important greenhouse gas,the transformation and utilization of CO₂ have a significant meaning on mitigating greenhouse effect and improving the ecological environment.Due to high stability of CO₂ molecule,traditional activation methods need high temperature to break the chemical bonds.Non-thermal plasma offers an attractive and promising alternative to the thermal catalytic route for the conversion of CO 2,which can provide a large number of high energetic electrons?1-10 e V?and radicals at room temperature.In this paper,dielectric barrier discharge?DBD?plasma has been developed for the conversion of CH₄ and CO₂ into higher value synthesis gas,meanwhile,graphitic carbon nitride?g-C₃N₄?was firstly combined with DBD plasma to improve the conversion efficiency.Main work and research results were as follows:?1?Conversion of CO₂ by coaxial dielectric barrier discharge?DBD?reactor has been studied,including discharge characteristic and effect of discharge power,temperature,feed gas flow rate.The results show that,the discharge mode of DBD was filaments discharge.And the conversion of CO₂ increases at first and decreases afterwards with the increase of discharge power.The conversion rate significantly improved under the cond ition of water cooling.The conversion of CO₂ decreases with the increase of flow rate,but the energy efficiency increases gradually.?2?Conversion of CH₄ by coaxial dielectric barrier discharge?DBD?reactor was investigated.The discharge characteristic and conversion of reactants under the condition of different kinds of inner electrode,various materials packing,feed gas ratio and gas flow rate were studied.Results indicate that,the initial voltage of reactor reduced in turn when the inner electrodes were rod electrode,bolt electrode and coil electrode,respectively.The optimum conditions obtained when inner electrode was bolt electrode.Conversion of CH₄ improved significantly as packing ?-Al2O3 bulks.Parameters of feed gas show obvious influence on the conversion reactions.The conversion of reactants decreases with the increase of feed flow rate.The ratio of H2/CO is only related with the ratio of CH₄ and CO₂ in the mix gas and increases along with the CH₄ ratio in the feed gas.?3?DBD plasma combined with g-C₃N₄-based composite for the conversion of CH₄ and CO₂ were carried out.Relatively low-cost and non-mental g-C₃N₄-based catalysts were prepared and combined with DBD plasma for the improvement of C H₄ and CO₂ conversion.In the DBD plasma/catalyst system,conversion of CO₂ and CH₄ increased from 11% and 20% to 16% and 28%,respectively.In DBD plasma,the catalytic activity of TiO₂/g-C₃N₄ composite decreases with the increase of TiO₂ proportion,and TiO₂/g-C₃N₄ with 1% TiO₂ mass ratio presented best catalytic performance in this experimental research system.