Catalytic Decomposition Of N₂O By Composite Metal Oxide

A series of MgxCeyCo1-x-yCo2O4 composite metal oxide catalysts were prepared by precipitation method and high temperature calcination method using nitrate as raw material and carbonate as precipitating agent.The catalytic activity of N20 was investigated.The results show that the Ce-Mg-Co composite metal oxide catalyst has the best catalytic decomposition of N20 activity in the study of a series of catalysts.Meanwhile,the effect of temperature,calcination time,and molar ratio on the catalytic performance was investigated,the results indicated that the composite metal oxide Mg0.025Ce0.05Co0.925Co2O4 calcined at 400?/3h has the highest catalyst activity at 250? which can completely decompose 35%N2O/He.According to the characterizations of the catalyst of BET,XRD,H2-TPR and XPS,the doping of Magnesium can change the spinel structure regularity and grain size.The Ce02 dispersion is good,which has a sort of interaction with magnesium oxide and cobalt oxide,thus decreasing the crystallinity and crystallite size and increasing the ratio surface area.As a result,this increased the redox ability of M90.025Ce0.05Co0.925Co2O4.Magnesium and Cerium addition changed the chemical environment of the catalyst of cobalt ions,thus significantly improved the Co2+ electron donating ability.Cerium addition also reduced the reduction temperature of Co3+ to Co2+,which thereby improved the concentration and mobility of oxygen on the surface of catalyst.Due to the improved surface oxygen compensation ability was improved,and further promoted the activity of the composite metal oxides was observed.In this paper,the composite metal oxide with the best performance was used to prepare the monolithic catalyst by using cordierite support.The in situ synthesis and conventional coating approach were employed for the monolith catalysts preparation.The activities of the prepared samples were further compared with each other.Additionally,the synthesis time and cordierite size were also taken into account during the catalytic performance evaluations.It is found that the in situ synthesized monolith catalysts exhibited much higher activity.Meanwhile,along with the increase of the synthesis time,the crystallinity of the prepared oxide is better.It is also much easier to form a dense oxide film on the cordierite surface.The activity of the monolithic catalyst prepared using a carrier cordierite size of 100 cpsi is much lower,which is due to less amount of metal oxide.However,as the cordierite size increased to 400 cpsi,the loaded metal oxide can cause channel blockage and resulted in a large pressure drop.Therefore,,it is recommended to use 200cpsi and 300cpsi under the cordierite as a carrier.We investigated the stability of the composite metal oxide and the monolithic catalyst.It was found that the prepared composite metal oxide had strong resistance to the CO,SO2.Similar high resistance to CO was also found for the monolithic catalyst which however exhibited the poor SO2 resistance.The long-term activity measurement suggests that both the composite metal oxide and the monolithic catalyst exhibited well stability,maintaining deN2O activity at nearly 99.9%.No significant decrease or even deactivation of the catalyst activity is found.This finding proves high stability and reliability of the prepared composite metal oxide catalyst monolith catalysts.