Synthesis And Properties Of Composite Mesoporous Cerium Oxide And Metal Loading

With the attention of environmental protection, it has been an important issue to remove Carbon monoxide (CO), which was produced by industrial production and exhaust emission of motor vehicle. Therefore, it is very important to study and exploit highly active catalyst for CO oxidation reaction.Cerium oxide (CeO2) was a rare earth metal oxide that has a unique atomic structure. It has been wildly applied in CO oxidation fileds due to its typical crystal structure, strong oxygen storage capacity, fast transfer of electronic (Ce4++e=Ce3+) and high redox capacity. However, the catalytic activity and thermal stability of CeO2was limited. Researches indicated that catalytic performance of CeO2was significantly improved by doped other metal in the CeO2.Inaddition, mesoporous CeO2has recently attracted great intresting since its large surface area, uniform pore size distribution, and high level of porosity favors diffusion of reactant as well as enhancement of catalytic activity.In this article, mesoporous CeO2was synthesized by hydrothermal and sol-gel method, respectively, and then got a series of metal doped CeO2by impregnation method. Those catalysts were characterized by X-ray diffraction (XRD), N2adsorption and desorption, H2temperature programmed reduction (H2-TPR), Fourier Transform Ifrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and O2temperature programmed desorption (O2-TPD). The activity of catalysts for CO oxidation was evaluated on the fixed bed flow reactor used the temperature programmed oxidation (TPO). The obtained results and conclusions as following:(1) Mesoporous CeO2synthesized by hydrothermal method with CTAB has larger surface area, more uniform pore size and higher catalytic activity, compared with that prepared by sol-gel method. CO could be oxided to CO2under a low temperature (210℃, blank sample temperature>600℃) by the catalyst used.(2)The composite catalysts M/CeO2was prepared by M (M=Co、Cu、Fe、Mn、 Na、Ni and Zn) doped in the mesoporous CeO2.The composite catalysts have better redox properties and adsorption oxygen ability, because of strong interaction between M and Ce. The catalytic activity for CO oxidation of the catalysts was extremely improved by these properties.(3) A series of composite catalysts with different content Cu was synthesized by Cu doped in the mesoporous CeO2. The results indicated that the compound (CuO)10%/Ce02has larger surface area, more uniform pore size, better redox properties and higher oxygen adsorption ability(CO was completely oxidized in the100℃). The catalytic activity for CO oxidation was significant enhanced due to the fast transformation of Ce4++Cu+�'Cu2++Ce3+and oxygen transfer rate.(4) The composite catalysts with different content Co shown higher activity due to the strong interaction between Co and Ce. The composite catalyst (Co304)50%/Ce02has more oxygen vacancies, which favored the fast transferring between surface adsorption oxygen and lattice oxygen. As a result, catalytic activity for CO oxidation was obviously increased(CO was completely oxidized in the102℃).