Study On Catalyst For Synthesis Of Diphenylamine By Condensation Of Aniline

Diphenylamine and its downstream products have good prospects for development in rubber,dyes,medicine and other industries.At present,the most common method of producting diphenylamine in industry is to use aniline as a single raw material to synthesize diphenylamine through condensation.The one-way conversion of aniline is low,and the active center of condensation is not clear.This article intends to investigate the catalyst for the preparation of diphenylamine by the condensation of aniline.At the same time,the active center and reaction mechanism of the catalytic reaction are discussed.H? was selected as the catalyst.The optimal silicon-aluminum ratio and calcined temperature was investigated.The results show that H? with silicon-aluminum ratio of 25 has better catalytic activity.The optimal calcined temperature is 550?.When calcined temperature was increased from 550?to 750?,the pore size of H? increased from 118.68 A to 283.19 A.However,due to the decrease in the amount of acid and B/L,the catalytic activity decreased.It shows that the amount of Br(?)nsted acid and strong acid in H? is closely related to the reactivity.H? was treated with HNO3 and HCl to remove non-framework aluminum and transitional aluminum to obtain better pore property.The study found that the pore volume and specific surface area of H? increased after treatment with inorganic acid of 0.5 mol/L.However,the amount of strong acid decreased from 0.242 mmol/g to 0.079 mmol/g(HNO3)and 0.100 mmol/g(HCl),and the amount of Bronsted acid decreased from 0.413 mmol/g to 0.090 mmol/g(HNO3)and 0.225 mmol/g(HCl).In the end,the yield of diphenylamine decreased.It is also confirmed that there is a correlation between the content of Br(?)nsted acid and strong acid and the catalytic activity.Comparing the modified effect of HNO3 and HCl,it is believed that the presence of halogen in HCl can promote the reaction.The modified effect of F,Cl and Br were investigated,and the two fluoric salts of NH4F and(NH4)2SiF6 were compared.The best modified condition is to treat the catalyst with NH4F of 0.125 mol/L.The amount of Br(?)nsted acid increased from 0.413 mmol/g to 0.493 mmol/g,but the amount of strong acid decreased.At this time,the yield of diphenylamine can be increased to 34.68%.According to the results of characterization,Br(?)nsted acid is the active center of the reaction.The experimental conditions were explored and the reaction mechanism was speculated.The best reaction temperature is 340?.Adding water to the raw materials can inhibit the reaction.After deactivation and regeneration,the activity of catalyst can be recovered basically.Aniline and phenol may react with the action of H?,which provides a new research direction for industrial synthesis.