Explorative catalyst screening studies on reforming of glycerol in supercritical water

An explorative screening study with Pt/CeZrO2, Ni/ZrO2, Ni/CaO–6Al2O3, NiCu/CeZrO2, and a CuZn alloy was carried out to investigate the influence of different catalysts on the carbon-to-gas efficiency and gas composition in the reforming of glycerol in supercritical water. Experiments were conducted at 255–270 bar in a continuous set-up, with temperatures ranging from 375 to 700 °C, a feed concentration of 10 wt%, and a residence time of 8–87 s. The catalysts promoted the decomposition of glycerol significantly. At 674 °C the conversion of glycerol without catalyst was approximately 40%, while in the presence of catalysts (almost) complete conversion was obtained. All catalysts promoted the water-gas shift reaction, while the ones based on Ni also promoted methanation. Visual coke formation was significant for Ni/ZrO2 and Pt/CeZrO2, which might be responsible for the observed reduction in activity at longer runtimes for these two catalysts. The specific surface area of all catalysts, apart from CuZn, decreased after contact with water at supercritical conditions. Except for NiCu/CeZrO2, XRD analysis indicated only minor changes in crystal structure of the supports, confirming the stability and suitability of these supports in supercritical water.