Catalytic hydrogenation of nitrobenzene to p-aminophenol over Ni/SiO₂and SO₃H-C/SBA-15 solid acid mixed catalyst

Mechanical mixed catalysts comprised of 20% Ni/SiO₂ and carbon-silica mesoporous composite functionalized with sulfonic acid groups (SO₃H-C/SBA-15) were used for hydrogenation of nitrobenzene to p-aminophenol. The effects of the mass ratio of Ni/SiO₂ to SO₃H-C/SBA-15, reaction pressure, temperature, stirring speed, and reaction time were examined. The catalysts were characterized by X-ray diffraction, H₂ temperature-programmed desorption, transmission electron microscopy, infrared spectroscopy, and thermal gravity analysis. The results indicated that Ni is uniformly dispersed on the support, forming a single active center. The SO₃H-C/SBA-15 solid acid with 40% carbon content exhibits the highest acid density. The mixed catalyst with a Ni/SiO₂ to SO₃H-C/SBA-15 mass ratio of 1:6 shows the highest activity. Under optimized reaction conditions of a reaction temperature of 120 °C, reaction pressure of 0.6 MPa, stirring speed of 1200 r/min, and reaction time of 3 h, the nitrobenzene conversion of 85.1% and p-aminophenol selectivity of 23.8% were obtained. The reaction result is comparable with those on most mixed catalysts containing Pt and solid acid reported in the literature.