Phosphorus-Modified NiMo/γ-Al₂O₃ Catalysts for Highly Efficient Hydrogenation of Methyl Acrylate

Development of an effective and low-loading Ni-based catalyst is of great significance for methyl acrylate (MA) hydrogenation to methyl propionate (MP), which is a crucial step in coal-based methyl methacrylate production. In this study, we prepared a series of phosphorus-modified NiMo/γ-Al2O3 catalysts with low loadings using the incipient-wetness impregnation method for efficient hydrogenation of MA. Multiple characterization techniques, including XRD, BET, XPS, TEM, H2-TPR, and in situ DRIFT, were employed to reveal the promotional effect of the phosphorus component on the physicochemical properties of the as-prepared catalyst. It was revealed that the introduced phosphorus species facilitated the dispersion of Ni and Mo elements, the prevention of NiAl2O4 formation, and the increase in catalytic surface area and reducibility. As a result, the yield and selectivity of MP could reach nearly 100% on the catalyst composition of 3 wt % Ni, 3 wt % Mo, and 4 wt % P (3Ni–3Mo–4P/γ-Al2O3) prepared using H3PO4 as the phosphorus source at 80 °C and 0.8 MPa, and the catalytic stability could be maintained for over 100 h. In addition, the loading amounts of Ni and Mo species could be reduced by 2/3 compared with our previously reported results. In situ DRIFT studies indicate that phosphorus modification enhances MA hydrogenation by aiding its strong adsorption and hydrogen activation on Ni–Mo active sites, leading to a faster surface reaction and MP formation.