Syngas Production via Steam–CO2 Dual Reforming of Methane over LA-Ni/ZrO2 Catalyst Prepared by l-Arginine Ligand-Assisted Strategy: Enhanced Activity and Stability

A highly dispersed supported nickel catalyst (LA-Ni/ZrO2), synthesized by a facile l-arginine ligand-assisted incipient wetness impregnation (LA-IWI) approach, demonstrates much superior catalytic activity and exceptional stability for steam–CO2 dual reforming of methane in comparison with the classical Ni/ZrO2 catalyst by the IWI method. The origin of the enhanced activity and stability of the developed LA-Ni/ZrO2 catalyst as well as the role of the Ni– (l-Arg) complex as the Ni precursor is revealed by employing diverse characterization techniques including X-ray diffraction (XRD), N2 adsorption (BET), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), CO chemisorption, temperature-programmed hydrogenation (TPH), and thermogravimetric analysis (TGA). The superior catalytic activity of the developed LA-Ni/ZrO2 catalyst to the classical Ni/ZrO2 can be ascribed to the higher Ni dispersion, intensified Ni–support interaction, the enlarged oxygen vacancies, as well as the increased t-ZrO2 content and enhanced reducibility of NiO led by oxygen vacancies. More interestingly, although a larger amount of coke depositing on the spent LA-Ni/ZrO2 catalyst in comparison with that on the spent Ni/ZrO2 can be observed by TGA and TPH measurement, the developed LA-Ni/ZrO2 illustrates much higher catalytic stability to Ni/ZrO2, ascribed to the superior thermal sintering resistance of Ni nanoparticles and the different coke morphologies confirmed by TEM images led by intensified interaction of Ni and the ZrO2 support. The much superior catalytic activity and stability of the developed LA-Ni/ZrO2 catalyst endows it to be a promising candidate for syngas production with diverse H2/CO ratios via steam–CO2 dual reforming of methane.