Study On The Redispersion And Anti-carbon Properties Of Pt/CeO₂ Active Components For Partial Oxidation Of Methane

Coalbed methane is an unconventional natural gas.It is a major source of accidents in coal mine and greenhouse gas,the use of coal-bed methane plays a very important role in the environment,safety and economy.Partial oxidation of methane（POM）to syngas as an exothermic reaction and it has the characteristics of mild reaction conditions and low energy consumption,the ratio of the syngas product is favorable for Fischer-Tropsch synthesis and methanol production reaction.Sintering and carbon deposition are inevitable problems in catalytic reactions for catalysis itself,good dispersion is particularly important for cost control,especially for precious metal catalysts.Therefore,carbon deposition resistance and redispersion are hot topics in catalysts.In this paper,a series of Pt-supported catalysts were prepared with cerium oxide as the support,and they were applied to study in catalytic performance of POM.And through a series of characterization methods such as XRD,CO-DRIFTS,TEM,XPS,H₂-TPR,the dispersion conditions of Pt in cerium oxide and the effect of alkaline ions on the carbon deposition resistance of the catalyst were studied.The main contents are as follows:1.The calcination method was used to prepare CeO₂ as a support,and the impregnation method was used to synthesize Pt/CeO₂.Using Pt/CeO₂ as a model,the redispersion of Pt on CeO₂ in different atmospheres and temperatures was studied.The experimental results show that Pt agglomerates in a reducing atmosphere,and during the reprocessing process,Pt were dispersed in both oxygen and nitrogen atmosphere.The agglomeration of Pt in the hydrogen atmosphere is mainly due to the reduction of Pt,while the dispersion of the oxygen atmosphere is the oxidation of Pt.The dispersion in the nitrogen atmosphere is due to the oxygen-supply ability of cerium oxide to form platinum oxide species on the surface of Pt and disperse at high temperature,but this does not occur in the inert support.It is found through H₂-TPR that the surface lattice oxygen of the catalyst changes after nitrogen atmosphere treatment,which shows that the surface lattice oxygen plays an important role in the redispersion process.However,the treatment of the nitrogen atmosphere causes the oxygen storage capacity of the cerium oxide to decrease,which leads to the decrease of the catalytic performance of the POM reaction.2.The impregnation method was used to prepare PtKx/CeO₂ catalysts with different K concentrations and applied to the partial oxidation of methane.The experimental results show that the addition of K increases the selectivity of hydrogen in the catalytic reaction and reduces the selectivity of carbon monoxide.This is mainly because potassium ions promote the water gas shift reaction.In addition,the presence of potassium ions increases the basic sites of the catalyst and reduces the carbon deposit content after the catalytic reaction...