Influence of CeO2 and La2O3 on properties of palladium catalysts used for emission control of natural gas vehicles |
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Authors: | Yile Li Xiaoyu Zhang Enyan Long Hongmei Li Dongdong Wu Li Cai Maochu Gong Yaoqiang Chen |
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Institution: | Key Laboratory of Green Chemistry & Technology of the Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, Sichuan, China |
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Abstract: | Pd/YZ-Al2O3 (Y and Zr modified Al2O3, and hereafter, labelled as Al) catalysts with 4 wt% additive CeO2 and/or La2O3 were prepared
and characterized by X-ray photoelectron spectroscopy (XPS), NO-temperature programmed desorption (NO-TPD), N2-adsorption/desorption
(Brunauer-Emmet-Teller BET method), X-ray diffraction (XRD) and CO-chemisorption. Catalytic activities for CH4, CO and NO conversion
were tested in a gas mixture simulated the emissions from natural gas vehicles (NGVs) operated under stoichiometric conditions. The results
indicated that all catalysts exhibited excellent catalytic performances for CH4 and CO oxidation and the promoting effect of CeO2 or La2O3 was
significant for NO conversion. XPS results showed that the electron density around Pd was increased by CeO2 and/or La2O3, the binding energy
of Pd 3d decreased as the order: Pd/Al>Pd/Ce/Al>Pd/La/Al>Pd/CeLa/Al. The electron-rich Pd showed Rh-like catalytic properties which
exhibited good activity for the reduction of NO. NO-TPD results showed that the addition of CeO2 and/or La2O3 increased NO adsorption on
surface, and promoted the conversion of NO. |
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Keywords: | NGVs under stoichiometric condition palladium catalyst XPS NO-TPD NO conversion methane conversion |
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