A comparative study of zirconia supported nickel and/or ruthenium catalysts for glycerol steam reforming

Abstract

The physico-chemical properties of Ni, Ru, Ru–Ni monoclinic ZrO2 catalysts were studied and their catalytic activities in the glycerol steam reforming reaction (GSR) were compared. The catalysts were prepared by the wet impregnation method, calcined at 600 °C and characterized using XRD, BET, H2-TPR and CO2-TPD techniques. The XRD analyses revealed varying crystallite sizes depending on the active phase nature and composition. The H2-TPR analyses demonstrated that the reducibility of the active metal oxide species and its dispersion were affected by the active phase composition. The CO2-TPD analyses revealed that surface modification following impregnation modified the basic properties of the catalysts. The catalytic activity tests (T = 400–700 °C, WGFR 9:1, flow rate of 0.025 mL/min) showed that the nickel based catalysts were active while the ruthenium based catalyst was inactive. Combining ruthenium and nickel over zirconia led to smaller Ni particle sizes and a better metal dispersion both of which contributed to higher H2 yields and an increased coke resistance. During 24 h on stream, the combined Ru–Ni/ZrO2 catalyst maintained a higher total glycerol conversion compared to the Ni/ZrO2 catalyst. Only filamentous coke was identified on the spent catalysts after the stability tests. For a higher water to glycerol feed ratio (WGFR 46:1), encapsulating coke was formed over Ru–Ni/ZrO2 leading to the blockage of active sites and a more rapid catalyst deactivation.