Hydrogen production by glycerol steam reforming catalyzed by Ni-promoted Fe/Mg-bearing metallurgical wastes

Abstract

The present work investigates the catalytic potential of a Ni-promoted Fe/Mg containing metallurgical waste for sustainable hydrogen production by glycerol steam reforming (GSR). The catalyst (Ni-UGS) was prepared through solid-state impregnation of Ni into the structure of metallurgical residue. Ni incorporation led to the formation of (Ni,Mg)O solid solution, (NiFe2O4) and/or a nickel iron mixed oxide (NixFe1-xO). GSR performed in a fixed bed reactor at T=580°C, P=1atm, steam to carbon ratio (S/C) of 3, and gas hourly space velocity (GHSV) of 20,600cm3 (STP) gcat−1h−1 led to a glycerol conversion to gaseous (Xg) of 87%, H2 yield (YH2) of 79%, and H2/CO molar ratio of 5.5. The catalytic performance of Ni-UGS containing 11.7wt.% Ni was found to be superior to that of an alumina supported Ni-based commercial steam reforming catalyst with higher Ni content (29.8wt.%): Xg=86%, YH2=71%, and H2/CO molar ratio of 4.1. A stable performance during 48h on stream was also obtained by using the Ni-UGS catalyst. Characterization of the used catalyst confirmed the low formation rate (∼2.7mgcokegcat−1h−1) of filamentous type carbon. The promising obtained results were mainly attributed to (i) superior dispersion of Ni particles due to the formation of (Ni,Mg)O solid solution and (ii) the presence of active magnesium and iron oxide species (e.g., MgO, Fe3O4, MgFe2O4 and (MgO)(FeO) solid solution) in the Ni-UGS catalyst which stimulate the water gas shift reaction and coke gasification. Regeneration by an oxidative treatment of the used catalyst in air was examined and analysis of the regenerated catalyst revealed complete coke removal together with recovery of initial crystalline phases.