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Fabrication Of Novel Mesoporous Co Based Catalysts And Their Catalytic Performance In CO Preferential Oxidation

Posted on:2013-03-15Degree:MasterType:Thesis
Country:ChinaCandidate:R H JinFull Text:PDF
GTID:2231330371996925Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
To investigate cheap metal-based catalysts to replace the noble-metal catalysts for CO PROX reaction is of great significance. Co-Ce based catalysts have recently been found to show high catalytic activity for CO PROX reaction. This paper aims at investigating new type mesoporous Co-based catalysts for catalyzing CO PROX reaction in excess H2.In this paper, a series of supported cobalt oxide catalysts on doped mesoporous cerium oxides, as well as the Co-Ce-Zr-Mn-O composite oxide were prepared to catalyze CO PROX reaction to eliminate the trace CO from H2-rich gases. The effects of structure-directing agent (SDA) type, dopant M type in Ce-M-O support, the content of various components in the catalysts and the presence of H2O and CO2in feed on the catalytic properties of catalysts. Moreover, the stability of the catalyst in simulated syngas was investigated. The main obtained results are as follows:1. Catalysts prepared by using cationic surfactant cetyltrimethylammonium bromide (CTAB) as SDA possess an ordered mesoporous architecture and exhibit much better catalytic activity compared with those prepared by using anionic surfactant ammonium dodecylbenzenesulfonate (ADBS) as SDA. So the ADBS doesn’t seem to be a suitable SDA for preparing catalysts for CO PROX reaction.2. The appropriate amount of zirconia into the ceria benefits the improvement in oxygen mobility of ceria and the dispersion of cobalt oxide on support. Over20wt%Co3O4/meso-Ce0.85Zr0.15O2catalyst,100%CO conversion can be observed at165-200℃. But with H2O and CO2addition into the feed, the catalytic activity decreased sharply.3. Among the studied Co/Ce-M-O (M=Zr, Mn, Fe, Sn and Ti) catalysts, the CO oxidation activity follows the order:Co/Ce-Mn> Co/Ce-Zr> Co/Ce-Fe> Co/Ce-Sn> Co/Ce-Ti.4.25wt%Co3O4/Ce0.9Mn0.1O2exhibits excellent catalytic properties and the100%CO conversion can be achieved at125-200℃. Even under simulated syngas, the complete CO transformation can still be maintained at a wide temperature range of190-225℃.5.100%CO removal could be observed at the temperature window of140-200℃over the Co0.4Ce0.85Zr0.15Mn0.10Oε catalyst, which is a little narrower than that on25wt%Co3O4/Ce0.9Mn0.1O2; But the former shows better catalytic performance for CO PROX reaction under simulated syngas, the almost complete CO removal could be achieved at175-225℃.6. The developed Co0.4Ce0.85Zr0.15Mn0.10Oε catalyst manifests good stability for CO PROX reaction:Both the CO conversion and the CO2selectivity over the catalyst have no obvious change during the CO PROX process under simulated syngas.7. The addition of MnOx with right content would definitely promote the catalytic activity for CO PROX through the improved redox behaviour of the catalyst. Moreover, the addition of MnOx into the composite also increased the specific surface area of the catalyst and enhanced the stability of the Co-based catalyst in the simulated syngas.
Keywords/Search Tags:Cobalt oxide, Mesoporous structure, Doping ceria, CO preferential oxidation, H2O and CO2tolerance, Simulated syngas
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