Preparation Of Highly Reducible Ce O₂,Ce_0.5Zr_0.5O₂and Their Catalytic Performance For Co Oxidation

CO catalytic oxidation is an effective pollutant elimination technology.It has extensive applications in exhaust gas purification,fuel cell raw gas purification,etc.CeO2 is a widely-reviewed CO low temperature oxidation catalyst,and its morphology,size and surface oxygen have significant effects on the catalytic CO oxidation performance.In this paper,Ceria in nanoscale(tubu,rod and cube)with different morphologies were prepared by hydrothermal method.Through the characterization,CeO2-T is a long and straight tubular structure with a length of 1?5 ?m and a diameter of 30?70 nm.The wall of the tube is composed of CeO2 small particles(<20nm);the rod-like CeO2-R is the structure with a length of 300 nm to 1 ?m and a diameter of less than 40 nm,which has a regular appearance.The cubic CeO2-C is a mixture of regular cubic CeO2 and nanoparticles with a side length of 40-280 nm.The activity of CeO2 with different morphologies for CO catalytic oxidation were investigated.The activity of CeO2-R was much better than that of the other two catalysts.When the space velocity was 12000 mL·gcat-1·h-1,T90%was 225?.According to the characterization results,it was considered that this was due to the presence of a large number of easily-reduced oxygen species on the surface of CeO2-R,and its specific surface area was large,thus it exhibited excellent catalytic activity.The effect of space velocity on the catalytic performance of CeO2-R was investigated.When the space velocity was 18000 and 24000 mL?gcat-1?h-1,T90%was 242? and 253?,respectively.Ce0.5Zr0.5O2 solid solution were prepared by citrate sol-gel method.The influence of calcination temperature were investigated.It is found that the specific surface area of Ce0.5Zr0.5O2 gradually decreased and the reduction of oxygen species was becoming easier with increasing the calcination temperature.Used to catalyze the oxidation of CO,its activity increased gradually with the increase of calcination temperature.When the calcination temperature was 1000?,Ce0.5Zr0.5O2 had the highest activity.When the space velocity was 12000 mL·gcat-1·h-1,T90%was 235?.Ce0.5Zr0.5O2-T and Ce0.5Zr0.5O2-NT with different morphologies were prepared by respecting hydrothermal method and liquid deposition-hydrothermal,respectively.Through the characterization,Ce0.5Zr0.5O2-NT is a spherical particle with large gaps between the particles and the distribution of particles is loose;Ce0.5Zr0.5O2-T is a tubular structure with a length of 200 nm to 1 ?m and a diameter of less than 50 nm.The morphology is regular.The CO oxidation reaction catalyzed by different morphologies of Ce0.5Zr0.5O2 was investigated.The activity of Ce0.5Zr0.5O2-NT was much better than that of the other two catalysts.T90%was 215? at a space velocity of 12000 mL·gcat-1·h-1.The higher activity of Ce0.5Zr0.5O2-NT can be attributed to the presence of a large number of readily reducible oxygen species on its surface.