Study On Decomposition Of CO₂ By Dielectric Barrier Discharge Plasma

Due to combustion of fossil fuels for energy and transportation,certain industrial process and human activities since the industry revolution,CO₂ emission was increasingly serious which is one of the major challenges facing mankind,and it has caused dramatical climate change like global warming,rise of sea level and so on.Consequently,the conversion and utilization of CO₂ was crucial and it is a hot spot attracted by the global attention.As the improtant carbon rescource,CO₂ can be converted to many value-added chemicals like like CO,CH₄,CH₃OH and so on.Direct decomposition of CO₂ to CO and O₂ is one of the important routes for the CO₂ conversion.There is a great challenge facing mankind in the conversion and utilization of CO₂ due to its chemical stablity.Many technologies have been developed for the conversion of CO₂ into high-value chemicals and fuels,including the thermal decomposition,electrochemical method and photochemical catalysis method.However,all of these technologies have different limations.The pyrolysis method must be carried out at high operating temperatures?1400-1800 ^oC?.Electricatalysis uses solar energy,but the disadvantage is that the CO₂ conversion efficiency is too low?<1%?.With the advantages of strong ability for activition,relatively cheap and durable catalyst materials,plasma technology has a wide application in CO₂ conversion,expecially in the decomposition of CO₂.Direct decomposition of CO₂ to CO has attracted increasing attention.However,CO₂ owes a highly stable chemical nature,and conventional catalytic and thermal approaches could not activiate the CO₂ molecules efficiently for CO₂ conversion and utilization.Dielectric barrier discharge?DBD?,with many promising properties,for instance,rich in energetic electrons,and non-equilibrium character,low energy cost,and unique ability to initiate both physical and chemical reactions at low temperatures,is an alternative to the conventional catalytic chemical process operating at high temperatures.It provides a new solution for the transformation and utilization of CO₂.This work reported on the direct decomposition of CO₂ to CO using self-cooling dielectric barrier discharge plasma reactor at low temperatures and ambient pressure.Key factors like packing materials,and operating premeters?discharge power,feed flow rate and discharge frequency?were investigated to gain insight into the decomposition process of CO₂ in the DBD plasma.Here are the main conclusions of this study.?1?A series of optimization experiments were carried out to investigated the influencing factors of CO₂decomposition in the self-cooling dielectric barrier discharge reactor with and with packing materials.It can be concluded that decreasing the feed flow rate while increasing the discharge power,and controlling the temperature of the circulating water as low as possible enhanced CO₂ decomposition.The CO₂ decomposition rate and energy efficiency reached 35.8%and 5.8%in the solid Al₂O₃ pellets packed reactor,respectively.?2?The intriduction of packing materials changed the discharge characteristics and enhanced the and the electric field strength and mean electron energy,and all of these changes are advantageous to high CO₂decomposition rate.Packing materials with higher dielectric premittivity,smaller beads size tends to enhance CO₂ decomposition.56.5%of CO₂ decomposition rate was obtained,at the discharge power of 55 W,when packing ZrO₂-CeO₂ pellets?2 mm?into the reactor,the combination of both ZrO₂ and CeO₂ plays an important role in the CO₂ decomposition in DBD plasma.?3?Packing foamed Ni and Cu mesh into the reactor changed the optimal discharge frequency,and made more stable discharge,and the CO₂ decomposition reached 49.5%and 48.6%,obtained the highest energy efficiency of 11.1%and 10.8%,respectively.It can be concluded that packing porous materials with good electrical and thermal conductivity promotes CO₂ decomposition greatly,this result is promising for the application in CO₂ decomposition using DBD plasma.?4?The best result of CO₂ decomposition rate and energy efficiency could not obtained at the same time.There is a balance between CO₂ decomposition rate and energy efficiency in the CO₂ decomposition.Discharge power is the most important factor that affects the CO₂ decomposition rate,while the gas flow rate is the main influencing factor for energy efficiency.Therefore,a suitable combination of discharge power and energy efficiency is needed in order to obtain an ideal CO₂ decomposition rate and energy efficiency value.