An excellent Pd-based nanocomposite catalyst for the selective hydrogenation of para-chloronitrobenzene

A partially reduced Pd/γ-Fe2O3 nanocomposite catalyst (Pd/γ-Fe2O3-PR) was prepared using PdO and ferric hydroxide colloidal particles as starting materials. This catalyst exhibited excellent catalytic properties for the selective hydrogenation of para-chloronitrobenzene (p-CNB) to para-chloroaniline (p-CAN). The selectivity to p-CAN reached 99.2% at complete conversion of the substrate and intermediates, and the hydrodechlorination of p-CAN was fully suppressed over Pd/γ-Fe2O3-PR. The byproduct aniline was derived from the hydrodechlorination of p-CNB and 4,4′-dichloroazobenzene intermediate, a new hydrodechlorination route. X-ray photoelectron spectroscopy characterization indicated an electron transfer from the partially reduced γ-Fe2O3 nanoparticles to the Pd particles in Pd/γ-Fe2O3-PR. IR-CO probe and CO chemisorption experimental results revealed that CO could hardly be chemisorbed on the Pd particles in Pd/γ-Fe2O3-PR under our experimental conditions, implying an electronic interaction between the Pd particles and γ-Fe2O3-PR nanoparticles, which may be a cause of the observed superior selectivity to p-CAN over Pd/γ-Fe2O3-PR.

Graphical abstractPd/γ-Fe2O3-PR exhibited superior selectivity to p-chloroaniline in the hydrogenation of p-chloronitrobenzene, and the catalytic hydrodechlorination of p-chloroaniline was fully suppressed.Figure optionsDownload full-size imageDownload as PowerPoint slide