Preparation Of CuO-CeO₂-ZrO₂/Cordierite Monolithic Catalyst And Study Of Catalytic Performance

In this paper,the CuO-CeO2-ZrO2/cordierite monolith catalysts have been prepared by impregnation reduction method and hydrothermal method,using porous cordierite ceramics as carrier,and the active component supported directly on the porous cordierite ceramics.The effects of processing parameters on the structural properties of monolith catalysts prepared by impregnation reduction method and hydrothermal method were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),BET surface area measurements and ultrasonic vibration.The catalytic performance of the as-prepared catalysts for CO oxidation were measured.Through the characterization and analysis of the porous cordierite ceramics prepared by gel-casting method,the comprehensive performance such as the porosity,thermal expansivity,compressive strength can satisfy the requirements of supporting the active component directly.Thus,the porous cordierite ceramics was used as the carrier of monolithic catalysts.It was found that impregnation way had a great influence on the distribution uniformity and adhesion of active substance on the substrate.The monolith catalysts prepared by ultrasonic impregnation method had better uniformity and adhesion strength.The dipping procedure also affects the morphology of catalyst particles.The coralloid granules reunited by wormlike granules were obtained by thermostat water bath heating impregnation.The flat spherical catalyst particles of 300-400nm with good dispersion were formed via ultrasonic impregnation method.According to the results,it was found that the catalysts prepared by impregnation reduction method had smaller grain size and better adhesion strength,which were spherical particles and fragmental shape particles assembled with ultrafine needle.The monolithic catalysts prepared by hydrothermal method had good uniformity,but the adhesion strength was poor.The shape of catalyst particles was irregular.The processing parameters influence greatly the structural properties and catalytic performance of the catalysts prepared by impregnation reduction method.The results indicate that reduction condition has an important influence on the shape of catalysts.Fragmental shape catalysts were formed when the impregnated samples were reduced in the thermostat water bath.However,spherical-like particles were obtained by ultrasonic-assisted in the reduction process.The introduction of ultrasonic resulted in smaller grains,larger specific surface area and better catalytic performance.Disc-shaped,bean-shaped and spherical-shaped catalyst particles were obtained under different calcination temperature.The grain size of catalysts has reduced and the catalytic activity for CO oxidation has been improved with the calcination temperature decreasing.The highest conversion rate can reach 99.07%when the catalysts are calcined at 300?.The catalysts prepared by adding different surfactants had different morphologies.The samples had best dispersion when the mixture of CTAB and PEG-1500 were used as surfactant.The addition of surfactant resulted in larger specific surface area and better catalytic activity for CO oxidation.The highest CO conversion can reach 96.26%.Hydrothermal conditions affect the properties of the monolithic catalysts prepared by hydrothermal method.The results show that,the grain size of catalysts has reduced and the specific surface area has increased with the hydrothermal temperature decreasing.The catalysts had smaller grain size and larger specific surface area when the crystallization time was 24h.The addition of precipitant can improve the uniformity and stability of the catalysts,and increase the specific surface area.The results of catalytic activity test show that the catalysts prepared by hydrothermal method has inferior catalytic activity.The highest CO conversion can reach 96.26%.The highest CO conversion rate is only 75%,which is far less than the catalysts prepared by impregnation reduction method.