| This dissertation focuses on partial oxidation of methane (POM) to syngas over Pt-Co/CaO-Al2O3 bimetallic catalysts. A series of techniques such as activity measurement, BET, XRD, H2-TPR, XPS, Raman, TEM and CH4 pulse reaction have been used to examine catalytic performance and the phys-chemical properties of the catalysts, regarding surface area, dispersion of catalytically active phase, redox property and catalyst structure. Combining the results of catalytic reaction and catalyst characterization, the roles of CaO promoter as well as small amount of noble metal, and the interaction between catalytically active compositions (Pt and Co) and its effect on the performance of the catalysts have been investgated. Furthermore, the mechanism of deactivation of Co/CaO-Al2O3, the catalyst without Pt addition has also been discussed. The main results of the study are summarized as follows:1) In the Pt-Co/CaO-Al2O3 catalysts, CaO is an effective promoter to improve activity and stability, while the addition of noble metal Pt can further greatly enhance the catalytic performance for POM reaction. The activity of the catalyst increases with Pt content in the range of 0.1%-0.5wt%, At higher Pt content (> 0.5wt%), however, the activity is decreased due to Pt addition.2) The long-time stability test demonstrates that the Pt-Co/CaO-Al2O3 catalyst with a Pt content of 0.5wt% possesses not only higher activity for POM but also excellent stability and resistance carbon deposition. Under the reaction conditions of T = 750℃, CH4/O2/Ar = 2/1/4 and GHSV = 100000 ml·g-1·h-1 the catalyst performs with the CH4 conversion of -85%, CO selectivity of -92% and undetectable carbon deposition during 100 h.3) As compared with Co/CaO-Al2O3 catalyst, the Pt-Co/CaO-Al2O3 catalyst has lower ignition temperation, better catalytic performance under low temperature and high space velocity conditions. The Pt-containing catalyst shows a good catalytic performance even with no pre-reduced.4) Thereis a catalytic synergy effect between Ptand Co species in the Pt-Co/CaO-Al2O3 catalysts. XPS results reveal that Pt interacts with Co and Pt is enriched on the catalyst surface.5) H2-TPR results show that the addition of 0.1 wt% Pt can remarkably improve the reducibility of the catalyst, and the reducibility increases with the Pt content. CH4 pulse experiments reveal that the addition of Pt can promote activation and decomposability of the CH4.6) XRD and TEM results indicate that the metallic Co particles of the reduced catalysts can be redispersioned due to the addition of Pt. A small amount of noble metal Pt can effectively decrease the Co particle size, however, the Co particle size increased when the amount of Pt increase to more than 0.5wt%.7) TPR, Raman and XPS characterization of the used catalysts indicate that the deactivation of Co/CaO-Al2O3 catalysts is due to the reoxidation of metallic Co and the formation of CoAl2O4 spinel phases under the reaction conditions, which can be suppressed by the addition of small amount of Pt. Maybe these could be related to the excellent catalytic stability of Pt-Co/CaO-Al2O3 catalysts.
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