Effect of alloy composition on catalytic performance and coke-resistance property of Ni-Cu/Mg(Al)O catalysts for dry reforming of methane

In CH4-CO2 reforming, the activity and coke resistance of hydrotalcite-derived Ni-Cu/Mg(Al)O alloy catalysts show strong dependence on Ni-Cu composition. At reaction conditions of T = 873 K, CH4/CO2/N-2 = 1/1/2, SV = 60 000 mL h(-1) g(-1), and TOS = 25 h, the alloy catalysts with bulk Cu/Ni ratio of 0.25-0.5 exhibit good activity, stability, and coke resistance, while those with lower and higher Cu/Ni ratios deactivate due to severe coking. The optimized Ni-Cu/Mg(Al)O catalysts show graphitic carbon which is only 1/85-1/136 that of Ni/Mg (Al)O, highlighting the efficacy of Ni-Cu alloying for coke suppression. Moreover, the Ni-Cu/Mg(Al)O catalyst of highest activity performs well at temperature as low as 723 K, appearing as an effective non-precious catalysts for low-temperature CH4-CO2 reforming. It is disclosed that a Cu composition of 25-45% is appropriate for the alloy catalyst to perform well. The results of activation energy measurement, CH4-TPSR/O-2-TPO, and CO2-TPSR/H-2-TER indicate that alloying Ni with Cu inhibits CH4 decomposition, and Cu provides sites for CO2 dissociation to yield more active oxygen species suitable for carbon gasification, consequently lowering coke deposition and enhancing catalytic stability.