Ethanol Steam Reforming For Hydrogen Production Over Nickel Based Catalysts

Ethanol steam reforming (ESR) has attracted increasing interest recently, since it could provide hydrogen source for fuel cells. In this study, the catalytic performance of nickel based catalysts derived from hydrotalcite-like compounds was investigated in ESR, and relevant characterizations were employed to discuss the connection between physical-chemical properties and catalytic activity.The Ni content had an obvious effect on the catalytic performance in ESR. The nickel based catalyst with 15 (wt)% Ni content gave the highest ethanol conversion and hydrogen composition. The difference in the Al content not only led to variation in the crystalline structures, reduction properties and acidity/basicity, also had an effect on the distribution of output gas products. The decrease in the Al content resulted in the transformation of Ni species from NiAl2O4 spinel to Ni-Mg-O solid solution, the elimination of strong acid sites, the decrease in the amount of weak and medium acid sites and lower reducibility of Ni2+. Either separate Ni-Mg-O solid solution or NiAl2O4 spinel exhibited inferior catalytic activity and stability, while 15-HT-0.2 and 15-HT-0.4 catalyst showed superior performance,which may have something to do with the special properties of hydrotalcite-like derived catalysts.Hydrotalcite-like derived catalysts exhibited excellent catalytic activity and stability in ESR. The composition of hydrogen increaseed as the reaction temperature, GHSV and steam/ethanol ration enhanced. The catalyst activity and stability tended to be declined, when the Ni/Mg ration decreased. In particular, the NiMg10 catalyst showed an inferior catalytic performance. XRD and TEM investigations indicate that the reduced catalyst containd less Ni0 metal and the used catalyst suffered serious metal sintering and coke. The results suggest that the NiMg10 catalyst was deactivating. The NiMg10 catalyst activity and stability improved a lot at higher reduction temperatures. The optimum reduction temperature was 1073 K, at which the catalyst showed the best coke resistance for ESR. Combining the results of XRD, BET, TPR and TEM with the influence of reduction temperature on the catalytic performance, the inferior activity was ascribed to the low nickel content, less amount of Ni0 species and dispersion of Ni0 particles.