Promotion of Rh-based La2Zr2O7 type catalysts with the transition metals to improve sulfur-tolerance in diesel reforming

Abstract

Several Rh-based La2Zr2O7 type catalysts promoted by the transition metals (Mn, Fe, and Co respectively) were synthesized and used to reform n-hexadecane (a diesel surrogate) that contains 50 ppm dibenzothiophene for hydrogen production. Compared to Co-LaZrRh and Mn-LaZrRh, the Fe-LaZrRh catalyst exhibited the best hydrogen extraction capability and sulfur tolerance. This is probably due to the introduction of Fe, which not only enhances the Rh dispersion, but also facilitates the formation of electron-deficient Rh sites and the generation of oxygen vacancies. Additionally, electron-deficient Rh sites can hinder the formation of an irreversible sulfur-metal bond, thus resulting in better sulfur tolerance and thermal stability. Finally, the generated oxygen vacancies may also activate steam to form surface active oxygen species, which help remove the deposited carbon on the catalyst surface. In summary, the developed Fe-LaZrRh catalyst performed the best in the steam reforming of n-hexadecane containing 50 ppm sulfur, which deserves further exploration for future applications.