C3H8O3 + 3H2O ⇔ 7H2 + 3CO2 ; ΔHo = 128 kJ/mol
This overall reaction involves glycerol decomposition and water-gas-shift reactions.
C3H8O3 → 3CO + 4H2 ; ΔHo = 250 kJ/mol
CO + H2O ⇔ CO2 + H2 ; ΔHo = -41 kJ/mol
Methanation reactions may also take place during this process. In the present work, metal-incorporated silica-aerogel (SA) based catalysts were synthesized following co-precipitation and impregnation routes and used in steam-reforming of glycerol for the first time. Performances of Ni, Co, Mo, Ag, and Cr incorporated mono-metallic, as well as Ni-Ru, Ni-Mg, Ni-Mo, and Ni-Fe incorporated bi-metallic catalytic materials with different metal ratios were investigated in a fixed-bed reactor in a temperature range of 470-1035oC. Effects of H2O/Glycerol ratio (W/G) in the feed stream (between 1-9) on the product distribution was investigated. Synthesized catalysts were characterized by N2-adsorption, XRD, SEM, TGA, and pyridine-adsorbed DRIFTS techniques. The highest hydrogen yields with minimum coke formation were obtained with the Ni and Ni-Ru-based materials. Results showed that methane formation was negligibly small. CO2/CO ratio in the product stream showed a maximum in the temperature range of 540-850oC. The highest hydrogen yield of 84.5% was achieved with a very low coke deposition (0.06 g/gcath) with the 10Ni-2Ru/SA catalyst at 550oC, with a W/G ratio of 9. Hydrogen yield was about 82.1% with the Ni/SA catalyst at the same conditions. A decrease in the W/G ratio to 3 caused a decrease in hydrogen yield to a value of about 68%. Results proved that silica aerogel was an excellent catalyst support, and Ni, as well as Ni-Ru-incorporated SA catalysts showed highly stable catalytic performances in glycerol reforming, with high hydrogen yields and low coke formation.