Hydrophobic Ni foam catalyst for nitrobenzene hydrogenation enhancement in micropacked bed reactors

Non-modified Pd/PDA/Ni foam, hydrophobic modified F₉-Pd/PDA/Ni foam, and F₁₇-Pd/PDA/Ni foam catalysts are successfully prepared and used for NB hydrogenation in micropacked bed reactors (μPBRs). The catalytic performance increases with the addition of water in the water–methanol mixed solvent. In the mixed solvent with 50 v/v% water, F₁₇-Pd/PDA/Ni foam can almost completely convert nitrobenzene (NB) with a yield of 95.9% at a mild 45°C. As the solvent contact angle of catalysts increases (87.5–141.5°), the enhancement ratios of NB conversion and AN yield are 28.9%–92.4% and 31.4%–106.5%, respectively. The space–time yield of AN in μPBRs reaches 1.873 kg·L⁻¹·h⁻¹·g⁻¹, which is 1–2 orders of magnitude higher than that of conventional reactors. The kinetic model of NB hydrogenation is established at the water–methanol system in μPBRs. The hydrophobicity of catalysts significantly improves the reaction rate of NB hydrogenation, and the reaction rate constant is increased by 69.9%.