Study On Synthetic Technology Of Rubber Antioxidant 7PPD By Sulfureted Pt/C

Using 4-aminodiphenylamine and methyl isoamyl ketone as raw materials,Pt/C as catalyst,N-?1,4-dimethylpentyl?-N-phenyl-p-phenylenediamine?antioxidant 7PPD?was prepared by reductive alkylation.The synthesis process was studied.Firstly,commercial activated carbons were characterized by SEM,N₂ physical adsorption,Boehm titration,laser particle size analysis,respectively.Suitable carrier?AC1?was selected as the carrier.The AC1 was modified by an oxidation treatment,a high temperature treatment and a hydrothermal treatment.The results show that with the increasing of oxidant concentration,the oxygen-containing groups on the surface of activated carbon increased significantly.But if the oxidation is too strong,the activated carbon structure would be destroyed.Under the protection of N₂,as the heat treatment temperature increased,the total amount of oxygen-containing groups on the surface decreased.Under hydrothermal conditions,as the temperature increased,the amount of carboxyl and lactone groups decreased,however the amount of phenolic hydroxyl increased.Pt/C catalysts were prepared by impregnation-reduction.The catalysts were characterized by TEM and ICP.The effects of preparation methods on the catalysts were investigated.The results showed that with the increasing of the theoretical loading,the loading ratio decreased,the particle size of the active metal nanoparticles increased and a slight agglomeration occurred.The liquid phase reduction method showed obvious agglomeration,and the gas phase reduction was more favorable.Different catalysts were used to the synthetic reaction of antioxidant 7PPD.The conversion of p-ADPA and selectivity of antioxidant 7PPD were obtained.The Pt-S/C catalyst had excellent catalytic performence which was prepared by the follow process.The AC1 was pretreated with 5%nitric acid and then loaded with 3%Pt.It was reduced by H₂ and sulphurated by diphenyl sulfide.The optimal reaction conditions using Pt-S/C were obtained as follows.The mole ratio n?methyl isoamyl ketone?:n?4-aminodiphenylamine?=6.0,the quantity of catalyst 2%for 4-Amino diphenylamine,the reaction temperature 130?,the reaction pressure 3.0 MPa,the stirring speed 600r/min.Under aforementioned conditions,the catalyst could be reused 26 times.The conversion rate of 4-Amino diphenylamine reached 99.5%and the yield of antioxidant7PPD reached 98.5%.Antioxidant 7PPD was prepared with recovered methyl isoamyl ketone.The results showed that repeated using of methyl isoamyl ketone had no effect on the catalyst and the synthesis of antioxidant 7PPD.The deactivated catalysts were characterized by CO chemisorption,laser particle size analysis,XRD,TEM,N₂ physical adsorption,respectively.Compared with the fresh catalyst,it could be concluded that the catalyst pore blockage was the main reason for deactivation.Regeneration was carried out by washing catalyst with solvent,such as 5%acetic acid,1%sulfuric acid,isopropanol,methyl isoamyl ketone and N,N-dimethylformamide.The results showed that N,N-dimethylformamide had the best regeneration effect,and the catalyst could be reused 19 times after regeneration.