CO₂ Methanation In Non-Thermal Plasma Aided By Ni-based Catalysts

People have overused the fossil energy since the industrial revolution.Green houseeffect broke up during this period because of excessive emissions of CO2.CO2 methanation could not only eliminate the effect of CO2 on the climate,but could produce CH4,a kind of clean energy which could transported by existing pipeline.More and more scientists are committed to do the research about CO2 methanation.But there is a difficulty that CO2 methanation is exothermic while activating CO2 needs a large amount of energy.In a word,the most important problem to be solved is how to let the reaction happen at lower temperature.DBD plasma could produce high-energy electrons which could activate gas molecules efficiently and the system could keep at lower temperature.In this paper,a systematic research about combined catalyst and DBD plasma acting on CO2 methanation was conducted.Investigate the synergy effect of the catalyst and plasma.The results showed that introducing Ni/ZSM5 catalyst to the discharge zone of plasma could enhance the reaction activity greatly.Compared with reacting in tube furnace by heating,CO2 methanation reacting in plasma could keep the system at low temperature and avoid the damage of surface properties by heating.In the aspect of catalyst preparation,support filtering,preparing conditions and reduction process of catalyst precursor were studied.Ni/ZSM5 exhibited the highest CO2 methanation activity thus Ni/ZSM5 was the object of study in the following investigation.On the basis of this,Ni loading level and calcination temperature in the process of catalyst preparation.The results showed that the catalyst activity was highest in the condition of Ni loading level 10%and calcination temperature 500?.The reduction effect of DBD plasma on catalyst precusor was inspected.With the DBD plasma and H2,Ni O could be reduced to Ni absolutely.Compared with reducted by thermal method,catalyst reduced by DBD plasma could exhibit higher activities while forming more micropores which benefited the absorption of CO2 and H2.The conditon of reduction process was then studied.The resluts showed that higher input power was conductive to Ni O transforming to Ni which benefited the activity of catalyst.Reduction time was ineffective on activity but could increase the surface specific area.For further improving the catalyst performance,additives were added to Ni/ZSM5.The influence of additives added to catalysts was inspected.The results showed that adding additives could all lower the catalyst activity.The order of catalyst activities added different additives was as follow: no additive>La>Cr>Zr>Ce>Mn>Fe.Based on this result,a series of catalysts added different amount of La were prepared.The results showed when the La loading level was 3%,the catalyst activity was highest.By charateraction,it was found that loading La could decrease the micropores.Though the crystalline grain of the catalyst was smallest when the La loading level was 4%,the activity decreased.It might be because that La covered the active sites on the surface.Investigate the reaction conditions and optimize the parameter.Results showed that in the condition input power 33.3W,feed gas ratio 1:5,space velocity 3600h-1,the CO2 conversion and CH4 selectivity could both get to 99%.