Hydrogen production from methane dry reforming on coke-resistant Pr-doped Co/mesoporous alumina catalysts

Abstract

Dry reforming of methane, DRM is largely recognized as a promising route for generating H₂ energy to substitute fossil fuels. In this work, the promotional effect of praseodymium dopant (0-7 wt %) on the performance and coking resistance of mesoporous alumina (MA)-dispersed Co catalysts was investigated at a stoichiometric DRM feed composition and 650–750 °C. Pr promotion considerably reduced Co₃O₄ crystal dimension from 16.8 to 7.8 nm and 5Pr10Co/MA possessed the smallest Co₃O₄ crystallite size. The total basic site concentration was boosted with Pr addition from 66.8 to 169.7 μmol CO₂ $g_{cat}^{-1}$. Stable CH₄ conversion with time-on-stream was evidenced on Pr-promoted catalysts (1 %-5 %Pr) because of enhancing basic site concentration and CO₂ adsorption. Notably, 5Pr10Co/MA achieved the greatest CH₄ (90.91 %) and CO₂ (82.13 %) conversions at 700 °C and exhibited the highest coke resistance with the least carbon deposition percentage (0.87 %) and carbon formation rate (2.42 × 10⁻⁵ $g_{carbon}{g}_{cat}^{-1}$ min⁻¹) owing to the smallest Co₃O₄ crystallite size, oxygen vacancy and redox attributes. An enhancement in H₂ yield from 52.52 % to 87.94 % was evidenced on 5Pr10Co/MA with rising temperature from 650 to 750 °C. The two-step mechanism for coke suppression triggered by a redox PrO₂/Pr₂O₃ pair was also elaborated in this study.