Hydrogen production from chemical looping steam reforming of glycerol by Ni-based oxygen carrier in a fixed-bed reactor

Abstract

Hydrogen production from chemical looping steam reforming (CLSR) of glycerol was studied by Ni-based oxygen carrier in a fixed-bed reactor. For the fixed-bed reactor configuration, solid Ni-based oxygen carrier is stationary and alternatively exposed to reducing and oxidizing conditions by periodically switching the feed gases. The Ni-based oxygen carrier was prepared by a liquid-state co-precipitation method with rising pH technique and the characterization was performed by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and N2 adsorption–desorption. Gaseous products and temperature variety during CLSR process by Ni-based oxygen carrier in a fixed-bed reactor were measured, and the thermodynamic equilibrium calculation was also carried out. The results showed that the Ni-based oxygen carrier synthesized has a dual function and can efficiently convert glycerol and steam to H2 by redox reactions. The coexisting reactions of glycerol oxidization (or NiO reduction) and steam reforming occurred before the steady stage of hydrogen production in the fuel feed step, and the conversion of NiO to Ni was obtained. Alternating reduction and oxidation reactions enabled Ni-based oxygen carrier to produce H2 with a concentration of 85% of the equilibrium value at 600°C, and glycerol conversion was up to 99%. The increase of temperature related to the exothermic reactions by Ni-based oxygen carrier in CLSR process was observed in redox cycles.