Effect of high surface area CeO2 and Ce-ZrO2 supports over Ni catalyst on CH4 reforming with H2O in the presence of O2, H2, and CO2
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Author list: Laosiripojana N., Chadwick D., Assabumrungrat S.
Publisher: Elsevier
Publication year: 2008
Journal: Chemical Engineering Journal (1385-8947)
Volume number: 138
Issue number: #
Start page: 264
End page: 273
Number of pages: 10
ISSN: 1385-8947
Languages: English-Great Britain (EN-GB)
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Abstract
Methane steam reforming over Ni on high surface area (HSA) CeO2 and Ce-ZrO2 supports, synthesized by surfactant-assisted method, was studied and compared to conventional Ni/CeO2, Ni/Ce-ZrO2, and Ni/Al2O3. It was firstly observed that Ni/Ce-ZrO2 (HSA) with the Ce/Zr ratio of 3/1 showed the best performance in terms of activity and stability. This catalyst presented considerably better resistance toward carbon formation than conventional Ni/CeO2, Ni/Ce-ZrO2, and Ni/Al2O3; and the minimum inlet H2O/CH4 ratio requirement to operate without the detectable of carbon are significantly lower. These benefits are related to the high oxygen storage capacity (OSC) of high surface area Ce-ZrO2 support. During the reforming process, in addition to the reactions on Ni surface, the redox reactions between the absorbed CH4 and the lattice oxygen (Ox) on CeO2 and Ce-ZrO2 surface also take place, which effectively prevent the formation of carbon on the surface of Ni. The effects of possible inlet co-reactant, i.e. H2O, H2, CO2, and O2 on the conversion of CH4 were also studied. It was found that H2 presented positive effect on the CH4 conversion when small amount of H2 was introduced; nevertheless, this positive effect became less pronounced and eventually inhibited the conversion of CH4 at high inlet H2 concentration particularly for Ni/CeO2 (HSA) and Ni/Ce-ZrO2 (HSA). The dependence of H2O on the rate was non-monotonic due to the competition of the active sites, as have also been presented by Xu [1], Xu and Froment [2,3], Elnashaie et al. [4] and Elnashaie and Elshishini [5]. Addition of CO2 inhibited the reforming rate, whereas addition of O2 promoted the CH4 conversion but reduced both CO and H2 productions. ฉ 2007 Elsevier B.V. All rights reserved.
Keywords
Carbon formation, Ce-ZrO2, Methane steam reforming
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