Kinetics of 4‑nitrophenol reduction with NaBH<sub>4</sub> over Ag/CuO nanomaterial catalyst

Abstract

In this paper, Ag/CuO nanomaterials were prepared via hydrothermal method combined with chemical reduction and used as catalysts in the reduction of 4-nitrophenol. Kinetic study of 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP) by sodium borohydride revealed a first order reaction. The reaction rate constant k increased with amount of silver crystals introduced into CuO nanosheets, with Ag/CuO catalyst concentrations and with temperature. The thermodynamic activation parameters such as activation energy (Ea), enthalpy of activation (∆H#), entropy (∆S#) and Gibbs energy (∆G#) of activation were determined. The value of Ea, ∆H#, ∆S# and ∆G# were 72,33 kJ/mol, –69,86 kJ/mol, –24,28 J/K.mol and –62,50 kJ/mol (303K), respectivement. Ethanol and isopropanol were able to inhibit the 4-NP reduction with NaBH4 in the presence of Ag/CuO catalyst.