Parametric study of reforming of glycerol to hydrogen over precious metal catalysts in a microchannel reactor

Abstract

The purpose of this study is to construct a system to conduct glycerol steam reforming experiments in a microchannel reactor and to investigate how different parameters (temperature, steam-to-carbon ratio, total flow rate and reactant composition) affect the glycerol conversion and selectivities of gaseous products. Three precious metal catalysts (2 wt.% Rh/Al2O3, 2 wt.% Pt/Al2O3 and 2 wt.% Ru/Al2O3) are prepared using incipient-to-wetness impregnation technique. Glycerol and water mixture is sprayed into the furnace with the help of inert gas, N2. The condensables are collected in cold traps and the gaseous products are analyzed by two gas chromatographs. It is observed that glycerol conversion increases with temperature over all three catalysts. Rh turns out to be the best catalyst in terms of glycerol conversion. Temperature is determined as the key parameter to glycerol steam reforming. Pt/Al2O3 at 475 °C and Rh/Al2O3 at 500 °C give maximum H2 selectivities. At high temperatures, H2 selectivities decrease; CH4, C2H4 and C2H6 selectivities increase. Temperature is determined as the key parameter to glycerol steam reforming. Steam-to-carbon ratio affects the products distribution via water gas shift. Higher steam-to-carbon ratios lead to higher H2 selectivities. Increasing total flow rate negatively affects glycerol conversion, but no significant changes are observed on gaseous product selectivities. Increasing the reactant composition in the system leads to a decrease in both glycerol conversion and H2 selectivity. Coke formation is inevitable in glycerol steam reforming. Over all three precious metal catalysts, even in blank tests, coke formation is observed. Amount of coke deposited is less on Rh-based catalysts. According to EDX results, targeted metal loading (2 wt.% Rh) is achieved in Rh catalyst. Spent Rh catalysts exhibit carbon formation, more carbon is deposited on entry region than exit region.