Sm6WO12 tungstate supported nickel-based catalysts with enhanced resistance to coking and oxidation in auto-thermal reforming of acetic acid†

Abstract

Hydrogen is an eco-friendly and renewable energy source with high energy density per mass and is expected to be an alternative to fossil fuels. As a main component derived from biomass, acetic acid (HAc) shows potential in green hydrogen production via auto-thermal reforming (ATR) of HAc. In the ATR process, although Ni-based catalysts exhibited high activity for the conversion of HAc, issues of oxidation, sintering and coking remain to be addressed. Therefore, nickel-based catalysts loaded on the Sm₆WO₁₂ tungstate structure were fabricated by the co-precipitation method, and the structure–reactivity relationship was explored. The characterization results showed that a stable Sm₆WO₁₂ tungstate structure was formed after the introduction of W species in Sm oxides, promoting reduction and dispersion of Ni on the catalyst surface with a high Ni⁰/(Ni⁰ + Ni²⁺) ratio of NSW20 at 40.8%. Meanwhile, abundant oxygen vacancies were formed in the tungstate structure, which accelerated the conversion of reactants H₂O and O₂ into active oxygen species (O*), and enhanced the oxidation of coking precursors (C*), thereby efficiently inhibiting coking of the catalyst. As a result, the NSW20 catalyst with a Sm₆WO₁₂ support exhibited high catalytic activity in the ATR process: the conversion of HAc was stable at 100.0%, and the yield of hydrogen was maintained near 2.42 mol-H₂ per mol-HAc, while the apparent activation energy (E_a) and turnover frequency (TOF-H₂) were recorded to be 43.5 kJ mol⁻¹ and 2.38 × 10⁻² s⁻¹, respectively.