Effect of impregnation protocol in the metallic sites of Pt-Ag/activated carbon catalysts for water denitration

The influence of the Pt precursor and the impregnation protocol in the catalytic behavior of 3%Pt-1.5%Ag supported on activated carbon for water denitration in a continuous reactor was studied. Pt(NH3)4(NO3)2 and H2PtCl6 were selected as Pt precursors. Five protocols were investigated: sequential impregnations (both sequences), co-impregnation, physical mixture of monometallic catalysts, and physical mixture of a bimetallic catalyst with a Pt monometallic catalyst. The samples were characterized by XRD, XPS, TPR, HRTEM and physisorption. It was found that the catalytic activity strongly depends on the synthesis protocol and the Pt precursor, which modify the particle size. Higher nitrate rates are achieved using H2PtCl6 than Pt(NH3)4(NO3)2; this is mainly related to the smaller metal particle size of the former, evidenced by HRTEM. Nitrate consumption rate is directly related with the mean particle size. The physical mixture of monometallic catalysts resulted in the highest nitrogen rate.