| Summary: | 碩士 === 國防大學中正理工學院 === 應用化學研究所 === 95 === A high valence cobalt oxide, CoOx has been prepared by the precipitation- oxidation method. Further, the nanosize cobalt was refined by controlling calcination temperature. The modified CoOx with lanthanum, La/CoOx(5, 10, 20 wt %) was prepared by impregnation method. The particle sizes and structures of catalysts were physically characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The technique of temperature programmed reduction (TPR) was used to explore the reductive behavior of the oxidized catalysts and inspected the interaction between lanthanum oxide and cobalt oxide. Evaluation of catalytic activities on steam reforming of ethanol(SRE) over cobalt catalysts were proceeded in a fixed-bed reactor. In order to find the optimal conditions of SRE and understand the mechanism of SRE over CoOx and La/CoOx catalysts.
Based on the XRD and TPR analysis, we found that both the phase compositions and the reduction temperatures(Tred) of species were affected with the calcination temperature(Tc). The higher Tc, increased the particle size and raised the Tred. Lanthanum modified cobalt catalysts could enhance the thermal stability and shift the Tred to high temperature. In SRE test, the CoOx possessed the best performance among the series of CoOx catalysts under TR = 375℃ and H2O/EtOH = 4, the yield of hydrogen(YH2 )approached 5.7 the selectivity of CO(SCO ) approached 1.6 %. The lifetime over CoOx catalyst only maintained 48 hr. Whereas, the lifetime of 10La/CoOx(H) catalyst exceeded 60 hr under TR = 425℃ and H2O/EtOH = 4, the yield of hydrogen(YH2 = 5.9 ) was competed with the theoretical value.
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