Effect Of Carbon Modification Of Support On The Catalytic Performance Of Pd-Cu/attapulgite Catalyst For Room-temperature CO Oxidation

CO is a toxic and harmful air pollutants,which not only endangers human health,but also is a precursor of ground-level ozone that can cause serious environmental problems.All of these environmental issues make the elimination of CO has become an important subject for the scientific researchers,the research of theory and application have been paid more and more attention.CO catalytic oxidation has been widely applied in the fields of industry,military,environmental protection and so on,such as vehicle exhaust treatment,CO2 laser,CO gas sensor,CO elimination in submarine and CO-PROX(CO preferential oxidation reaction)for proton exchange membrane fuel cell(PEMFC),which mainly results from its high efficiency,low energy consumption and non-polluting.In addition,the reaction of CO oxidation is often used as a model reaction in the theoretical research to reveal the relationship between catalyst properties,phase composition,grain size,morphology and the performance of catalyst.Therefore,the research of CO catalytic oxidation is of great significance for practical application and theoretical exploration.There are three main types of CO catalysts for low temperature oxidation: noble metal catalyst,non noble metal oxide catalyst and supported Wacker catalyst.The supported Wacker catalyst(Pd Cl2-CuCl2/support)is rich in Cl-and water molecules participate in the reaction cycle.The catalyst can exhibit high CO catalytic oxidation activity and excellent water resistance and anti-halide poisoning even in the presence of water vapor and halide in the feed gas.There are a lot of studies have shown that the catalytic performance of catalyst is related to the nature of support,and the supports of Wacker catalysts are mainly activated carbon,alumina,attapulgite etc.The influence of calcination treatment,ultrasonic treatment of support and preparation method on the catalytic performance of Pd-Cu/APT were studied in our previous work,and we found that the calcination treatment can greatly promote thecatalytic oxidation performance of the catalyst;The ultrasonic treatment of support can improve the hydrophobicity of the catalyst and improve the stability of the catalyst;Compared with the catalyst prepared by the impregnation method,the catalyst prepared by the ammonia evaporation method exhibits higher catalytic activity.However,the catalyst shows poor stability under the condition of high moisture content or long time reaction.In this paper,the attapulgite was modified by glucose and sucrose,the effects of water vapor content,carbon temperature and carbon source content on catalytic performance of Pd-Cu/APT catalyst for CO oxidation were studied.TG?XRD?N2-physisorption?Raman?FT-IR?H2-TPR?CA were used to characterize the texture,morphology,active species,redox properties and hydrophobicity of the catalyst,thus the relationship between structure and the catalytic performance of the catalyst was understood.The main results and conclusions of this paper are as follows:1.Effects of water vapor content,carbon temperature and carbon source content on catalytic performance of Pd-Cu/APT for CO catalytic oxidationThe unmodified catalyst and carbon modified catalyst exhibit high stability under the conditions of CO 0.5%,GHSV 6000 h-1 and water vapor content 1.8%.However,under the condition of water vapor content of 3.3%,the carbon modified catalyst exhibits better stability.PC/APT-G-0.1 and PC/APT-S-0.1 catalysts show the excellent catalytic performance under the reaction conditions of CO 0.5%,GHSV 8000 h-1,water vapor content 3.3%.Both of the CO conversion rate can reach100%,and CO can be converted completely in 150 min.Therefore,the carbon modification of attapulgite can effectively improve the catalytic performance of the catalyst.2.Effect of carbon modification of attapulgite on the structure and properties of Pd-Cu/APT catalystThe results show that the carbon species can be successfullyintroduced into the attapulgite by pyrolysis of sucrose,the carbon species has a certain influence on the specific surface area,average pore size and pore volume of the support and catalyst,which promotes the dispersion of Cu2Cl(OH)3 in the catalyst and enhances the content of active Cu species.Especially,the catalyst surface hydrophobicity is properly improved after carbon modification.Thus,the carbon modified catalyst exhibits an excellent catalytic performance at high concentration of water vapor or high GHSV.