Comparative study of MxOy (M = Cu, Fe and Ni) supported on dolomite for syngas production via chemical looping reforming with toluene

Abstract

Syngas is an indispensable chemical raw material, which also can provide heat and power. Chemical looping reforming (CLR) with biofuels is one prospective method to produce syngas. MxOy of 20 wt% (CuO, NiO and Fe2O3) supported on dolomite were prepared by the wet impregnation method used as the oxygen carriers (OCs) for syngas production in the CLR process with toluene in the lab-scale fixed bed reactor. The effects of the reduced temperature in FR and mass of OCs on the fuel conversion, syngas production and OCs utilization were studied. The study found that CuO/dolomite (CD) tended to generate CO2, while Fe2O3/dolomite (FD) and NiO/dolomite (ND) were appropriate to syngas production. Although CD achieved the highest oxygen effective conversion of 95.90% at 950 °C and the best selectivity for CO2, it was not a suitable OC for syngas production in CLR process since the cold gas efficiency, syngas yield and syngas purity for CD remained lowest under different reaction conditions. FD manifested the best performance at 900 °C with 30.0 g, exhibiting the highest cold gas efficiency and syngas yield of 54.23% and 1.16 Nm3/L, and the corresponding syngas purity was 73.86%. The selection of temperature and mass of FD played a key role in the quality control of syngas. Low syngas purity and rapid deactivation in cyclic tests were main barriers for FD to behave as an excellent OC in the CLR process. Furthermore, ND was the most ideal OC of the three for syngas production with the optimum condition being at 900 °C with 20.0 g, the corresponding cold gas efficiency, syngas yield and syngas purity were 39.30%, 0.93 Nm3/L and 90.59% respectively. ND exhibited the highest syngas purity of the three, and the satisfied H2/CO ratios (around 2.0) were achieved under different reaction conditions.