Cu@SiO2 catalyst with high copper dispersion for chemoselective hydrogenation of p-chloronitrobenzene

Selective hydrogenation of p-chloronitrobenzene (p-CNB) is not only of significant industrial importance, but also an important model reaction for selectivity investigation. Despite non-precious metal Cu has been proven to be an effective promoter in bimetallic catalysts, Cu as a single active metal achieving both high conversion and high selectivity are rare reported. In this work, Cu@SiO2 catalysts with high specific surface area (509.8–694.3 m2/g), high Cu dispersion (58.4–69.6 %), and small particle size (2.0–3.0 nm) has been prepared by a simple sol–gel method. The catalysts completely suppress the dechlorination reaction, achieving complete conversion of p-CNB with 99.9 % selectivity for p-chloroaniline (p-CAN). Its microstructure, composition, chemical state, adsorption and reaction behavior have been identified by various conventional ex-situ characterizations of catalysts and in-situ DRIFTs of hydrogenation of p-CNB. Interestingly, even at high loadings, Cu in the catalyst could be highly dispersed, thus exhibiting good catalytic activity. In addition, the Cu catalyst exhibits unique adsorption performance towards p-CNB, which perhaps one of the factors for its good performance. This work not only provides a selective hydrogenation catalyst with high Cu dispersion even at high loading amount by a simple method and but also reveals the importance of the adsorption mode of p-CNB, providing guidance for the development of more efficient catalysts in the future.