Upgrading renewable biogas into syngas via bi-reforming over high-entropy spinel-type catalysts derived from layered double hydroxides

Abstract

The bi-reforming of biogas is of great significance for the consumption of greenhouse gases and the generation of valuable syngas. In this study, porous high-entropy spinel-type HE-MgAlO (up to quinary metals: Ni, Co, Zn, Ga, Mn,) catalysts derived from layered double hydroxide were prepared by the one-step co-precipitation method. The catalysts were characterized comprehensively via XRD, XRF, H2-TPR, CO2-TPD, XPS, SEM, HR-TEM, STEM-EDS, CH4-TPSR/CO2-TPO, TG-DSC, Raman, and so on. Compared to the monometallic Ni/MgAlO and binary NiCo/MgAlO catalysts, the HE-MgAlO catalyst exhibits higher initial CH4 (∼98 %) and CO2 (∼55 %) conversion and high stability up to 100 h under certain reaction conditions. The homogeneously-dispersed and electronically-enriched Ni sites, the oxophilic property and medium-strong basic sites of HE-MgAlO catalyst, lead to efficient activation of CH4 and CO2 (H2O), respectively, and high catalytic activity ultimately. The generation of reactive O* from CO2 (H2O) over oxophilic and medium-strong alkaline sites of HE-MgAlO catalyst prompts the rapid removal of coke precursors, leads to satisfying coke-resistant behavior. The spinel structure and strong metal-support interaction in HE-MgAlO catalyst enhances the thermal stability and results in satisfying anti-sintering performance.