Preparation Of Metal (Ag?Ni?Cu)/ Oxides Xerogel Catalysts And Their Catalytic Performance Of P-nitrophenol To P-aminophenol

With the rapid development of the chemical industry,the demand of p-aminophenol?PAP?is increasingly growing.The direct catalytic hydrogenation of p-nitrophenol?PNP?is employed widely because this method may be an efficient,eco-friendly and sustainable method for the preparation of PAP.In previous works,noble metal catalysts have already been used as catalysts for this reaction.Non-noble metal catalysts which have been used for the hydrogenation of PNP are drawing increasingly attention since it is cheap,chemically stable and highly active.The aim of the paper was to study the synthesis of the metal supported on oxides xerogel composites nanomaterials and the application for catalytic hydrogenation of PNP to p-aminophenol PAP.A facile two-step approach involving sol-gel method followed by calcination or chemical reduction method was used.This study also provided an important insight into choosing the high activity,high selectivity,chemically stable composites nanomaterials.The main results experimental are as follows:1.A facile two-step approach involving sol-gel method followed by calcination was utilized.The amount of AgNO₃ and TEOS?C9H₂1AlO₃?was regulated to obtain Ag-SiO₂?Ag-Al2O₃?xerogel catalysts?2 wt.%,5 wt.%?.Several techniques were utilized to characterize the catalysts.The results showed that Ag NPs were successfully decorated on to the surface of SiO₂ and Al2O₃ samples.The minimum specific surface area was obtained for the 5 wt.% Ag-Si O₂ catalyst?288.417 m2/g?.The catalytic reduction of PNP to PAP was chosen as the model reaction to evaluate the catalytic activity of the Ag-based xerogel catalysts.The catalytic mechanism was proposed according to the Langmuir-Hinshelwood?LH?model.The pseudo first-order kinetics which was respect to the concentration of PNP can be applied to evaluate the Ag-based xerogel catalysts catalytic rates.The order of catalytic activity of the Ag-based xerogel catalysts is 5 wt.% Ag-SiO₂>5 wt.% Ag-Al2O₃>2 wt.%Ag-SiO₂>2 wt.% Ag-Al2O₃.After 5th cycles,the catalytic hydrogenation conversion of PNP to PAP catalyzed through the prepared 5 wt.% Ag-SiO₂,and 5 wt.% Ag-Al2O₃ xerogel catalysts remained 84 %,81 %,respectively.2.Based on NiCl₂·6H₂O?Ca?NO₃?₂·4H₂O and Al?NO₃?₃·9H₂O as raw materials,Ni?Ni-Al2O₃ and Ni-Ca-Al2O₃ xerogel catalysts were prepared were successfully synthesized viathe fast sol-gel process and chemical reduction method.The prepared samples were measured for further analysis through a variety of characterization methods.The catalytic reduction of PNP to PAP was chosen as the model reaction to evaluate the catalytic activity of the Ni-based xerogel catalysts.The results indicated that Al2O₃ can mitigate the agglomeration of the nickel and the addition of Ca can improve nickel dispersion,decrease nickel particle size.Langmuir-Hinshelwood?LH?model was proposed to evaluate the catalytic rates of the Ni-based xerogel catalysts using the pseudo first-order kinetics.The catalytic activity order of the three kind xerogel catalysts is Ni< Ni-Al2O₃ < Ni-Ca-Al2O₃.The nickel-based xerogel catalysts can be recycled advantageously since they possess soft magnetic in order to investigate the reutilization.After 5 cycles,the conversion of PNP to PAP catalyzed by Ni,Ni-Al2O₃,Ni-Ca-Al2O₃ remained 85%,82%,80%,respectively.The study shows that Ni-Ca-Al2O₃ have the best catalytic properties in the reduction of p-nitrophenol.3.The amount of Cu?NO₃?₂·3H₂O and TEOS?C9H₂1AlO₃?was regulated proportionally.the X wt.% Cu-SiO₂?X = 0,1,5,10,15 and 20?xerogel catalysts have been successfully synthesized via a facile two-step approach involving sol-gel method followed by chemical reduction.The prepared samples were furtherly analyzed through a variety of characterization methods.The catalytic reduction of PNP to PAP was chosen as the model reaction to evaluate the catalytic activity of the Cu-based xerogel catalysts.The results indicated that Cu2+ has been converted to metal Cu loaded on the surface of SiO₂.Among them,the 10 % Cu-SiO₂ xerogel possessed the smallest Cu NPs size and highest dispersion.Even after five recycle experiment,the conversion of PNP to PAP catalyzed by the 10 % Cu-SiO₂ xerogel catalyst remained 83%.