Ultra-low amount of Ag substantially improves the stability for dry reforming of methane on Ni/Ag/MgAlO bimetallic catalyst

Abstract

Ni, Ag bimetallic catalysts with different impregnation sequence were applied to dry reforming of methane (DRM) reaction. When the molar ratio of Ag/Ni was only 1/19, ultra-low amount of Ag not only greatly improved the stability of Ni catalyst, but also did not reduce the methane and CO₂ conversions. The impregnation sequence of Ag had an important effect on the activity and stability of DRM reaction as well as the physical and chemical properties of Ni, Ag bimetallic catalysts. Ni/Ag/MgAlO synthesized by first impregnating Ag and then Ni had the highest activity and stability in DRM reaction. CH₄ conversion only decreased slightly from 94.5 % to 90.2 % and CO₂ conversion from 96.3 % to 92.7 % after reacting for 26 h at 800 ℃. Ag effectively mitigated the amount of carbon deposition by inhibiting the nucleation and growth of whisker carbon. Ag also enhanced the interaction between Ni and MgAlO, preventing the aggregation of Ni species. Ni/Ag/MgAlO first impregnated Ag and then Ni had the strongest interaction among Ni, Ag and MgAlO, the smallest Ni0 particle size, and produced the least amount of carbon deposition, finally immensely improved the stability of DRM reaction without decreasing the DRM reaction activity.