Solvent-Controlled Reactivity of Au/CeO₂ Towards Hydrogenation of p-Chloronitrobenzene

Abstract: The solvent effect on catalyst activity and selectivity for the hydrogenation of para-Chloronitrobenzene (p-CNB) over Au/CeO₂ catalyst was investigated. Reaction over Au/CeO₂ generated p-chloroaniline as the sole product, whereas the p-CNB hydrogenation rate extremely hinged on solvent via modification of apparent activation energy (E_a) and pre-exponential factor (A). The apparent activation energy and the pre-exponential factor in different solvents followed the order: ethanol > i-butanol > s-butanol > t-butanol > t-pentanol, which linearly correlated with the hydrogen bond donation ability of solvents. Moreover, the constable plot was firstly found in the solvent effect on supported gold catalyst. From the ATR-FTIR analysis, N–O bond in p-CNB was strongly affected by the solvents via hydrogen bond compared with the benzene ring and C–Cl bond, thereby weaken the adsorption of the p-CNB on Au catalyst, inducing the increment of activity of p-CNB hydrogenation. These findings could provide a criterion to compare the performance of various catalysts in different solvents and a guideline to designate an appropriate solvent. Graphical Abstract: [Figure not available: see fulltext.].