Syngas production in chemical looping reforming process over ZrO2 promoted Mn-based catalyst

Abstract

Chemical looping reforming (CLR) of methane is a familiar process for the production syngas or hydrogen, which could be applied as one of the most important energy sources. In this process, reforming of methane takes place in the fuel reactor in contact with lattice oxygen of oxygen carriers (OCs), while the reduced OCs are re-oxidized in the air reactor. In this study, two different alumina supports are promoted using zirconium oxide to improve Mn-based oxygen carriers. Different synthesized oxygen carriers were evaluated in CO2-modified chemical looping reforming process at different conditions such as reaction temperature (500–750°C), CH4/CO2 ratio (0.5–3), alumina support base, ZrO2 position and manganese loading weight percentage (10–30). The presence of ZrO2 in the support structure significantly inhibited the deposition of coke on the surface of oxygen carrier. The characterization and process results revealed the noteworthy effect of Zr incorporation to the structure of alumina support. The redox results revealed that 20Mn/20Zr-Al oxygen carrier exhibited the highest activity even at low reduction temperatures. This oxygen carrier exposed the highest activity and stability with lowest coke deposition during 16 redox cycles at 650°C. The methane and CO2 conversion, H2 yield and H2/CO molar ratio of about 99.0%, 96.6%, 65.2% and 2.55 were achieved at 650°C using the optimized oxygen carrier. The synthesized samples were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and N2 adsorption–desorption (BET) techniques.