Combustion Suppression in Low-Temperature Electro-Catalytic Tri-Reforming of Methane over Ni-Mg Supported Catalysts

For reduction of automobile fuel consumption, a novel method for fuel reforming uses waste heat and exhaust gas components to regenerate the exhaust loss energy. We have investigated tri-reforming of CH₄ (TRM) using H₂O, CO₂, O₂, and CH₄ as model gas. TRM comprises three reactions: CH₄ steam reforming (SRM), CH₄ dry reforming (DRM), and CH₄ combustion (MC). To be suppressed to recover the enthalpy, SRM and DRM are expected to proceed preferentially to CH₄ combustion (exothermic).

Recently, our group reported that Co-impregnated catalysts of Ni and Mg on La-ZrO₂ (LZO) showed high reforming activity, suppressed CH₄ combustion, and achieved enthalpy recovery at 473 K by applying an electric field.

In this study, to elucidate the causes of high reforming activity and CH₄ combustion suppression over NiO-MgO co-supported catalysts in the TRM reaction in an electric field at 473 K, the reactivity and structure of NiO-MgO/LZO catalysts with or without an electric field was investigated using various experiments such as SRM activity and MC activity, and various characterization such as H₂-TPR, XRD, XPS, XAFS. As a result, we found that Mg addition to 10wt%Ni/LZO catalyst suppresses methane combustion, while SRM proceeds well by virtue of surface protonics in the electric field. NiO-MgO solid solution formed on the support played an important role in combustion suppression. Ni²⁺ on 10wt%Ni/10wt%Mg/LZO catalyst was more cationic than that on 10wt%Ni/LZO catalyst.