Kinetics and mechanism of reduction of nitrobenzene catalyzed by silver-poly(N-isopropylacryl amide-co-allylacetic acid) hybrid microgels

The aim of this study is to investigate the kinetics and mechanism of reduction of nitrobenzene using novel silver-poly(N-isopropylacrylamide-co-allylacetic acid) hybrid microgels as catalyst. For this purpose effect of catalyst dosage, concentration of nitrobenzene, concentration of sodium borohydride (NaBH4) and temperature on value of apparent rate constant (k(app)) was studied. The value of k(app) linearly increases from 0.083 to 0.313min(-1) by increasing catalyst dosage from 66.66 to 102.56 mu g/L at 305 K. Initially value of k(app) increases with increase in concentration of NaBH4. After reaching maxima the value of k(app) decreases with increase in concentration of NaBH4. Similar trend in the value of k(app) was observed in case of nitrobenzene. Retardation in value of k(app) at very high concentrations of reagents indicates that catalytic reduction obeys Langmuir-Hinshelwood mechanism. k(app) shows non-linear dependence on temperature. Initially the value of k(app) increases by increasing temperature upto 308 K due to Arrhenius behavior of reaction. On further increase in temperature upto 312 K the value of k(app) decreases due to deswelling of hybrid microgels. While the value of k(app) increases again with increase in temperature above 312 K. Hybrid microgels were characterized by FTIR, DLS, TEM, XRD and UV-Visible spectroscopy. (C) 2016 Elsevier B.V. All rights reserved.