Facile synthesis silver nanoparticles on different xerogel supports as highly efficient catalysts for the reduction of p-nitrophenol

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The paper addresses the effect of support on the structure and catalytic activity of Ag catalysts supported on SiO2, Fe2O3 and Al2O3 xerogel for catalytic reduction of p-nitrophenol. In order to study support effect of Ag catalysts, Ag-based xerogel catalysts (2 wt.%, 5 wt.%) were prepared by a facile two-step approach involving sol-gel method followed by calcination, and several techniques were employed to study the influence of different supports on the catalytic structure and reaction performances. The results showed the selected support is the main factor to determine the porous characteristic, porosities and the catalytic properties of the corresponding catalyst. Moreover, Ag-based xerogel catalysts on different supports were used for the conversion of p-nitrophenol (PNP) to p-aminophenol (PAP). The presence of different oxides as supports played a crucial role in the activity of Ag nanoparticles as reduction catalysts. The results revealed that 5 wt.% Ag based catalysts exhibited better catalytic activity for the reduction of PNP to PAP with sodium borohydride at room temperature. The reduction reaction followed the pseudo first-order kinetics. The order of rate constants of the 5 wt.% catalysts was Ag-Al2O3 < Ag-SiO2 < Ag-Fe2O3. It was found that these types of Ag-based xerogel catalysts can be used repetitively up to five times with no significant activity loss in the initial reduction rate.