Ni-Fe/La2O3 bimetallic catalysts for methane dry reforming: Elucidating the role of Fe for improving coke resistance

Abstract

Dry reforming of methane (DRM) offers an effective approach for converting two cheap undesired greenhouse gases into valuable chemical feedstock of syngas. In this work, with the objective to obtain high efficiency Ni-based catalyst with superior coke resistance, a series of 6Ni-xFe/La2O3 catalysts were prepared by co-impregnation method, and were applied to DRM reaction. Effects of Fe doping, support contents, Ni dispersion on DRM performance of 6Ni-xFe/La2O3 catalysts were investigated. X-ray diffraction analysis and STEM-EDS mapping revealed that Ni-Fe alloy particles were well formed in the fresh reduced 6Ni-xFe/La2O3 catalysts. H2-TPR results showed that the addition of Fe can enhance the interaction between and Ni active sites and La2O3 support. In-situ Raman and TGA-DSC results demonstrated that the amount of La2O2CO3 species increased rapidly during DRM stability test on the spent Ni/La2O3 catalyst, leading to an obvious accumulation of carbon deposits. With the promotion by Fe, the reaction between the La2O2CO3 species and carbonaceous deposits can be accelerated, which results in more active and stable catalysts with significantly improved coking resistance. In addition, more oxygen vacancies could be obtained on Ni/La2O3 catalyst by Fe doping, as evidenced by the XPS results. It was concluded that these were the major reasons accounting for the significantly improved coke resistance for the 6Ni-xFe/La2O3 catalysts.