Study On Synthesis Of P-phenvlenediamine

p-Phenylenediamine has been used in the manufacture of azo dyes,sulfur dyes,fur stains,rubber antioxidants,photo developers,fuels,synthetic resins and epoxy resin curing agent and other fields.However,there are some disadvantages such as harsh reaction condition,large discharge of waste and high cost in the industrial synthesis processes of p-phenylenediamine.It is of great practical significance to explore a new synthesis route with mild conditions,less waste discharge and low cost.Herein,a new synthetic route was put forward based on the application areas,market conditions and synthesis methods in this paper.With choosing nitric oxide gas as raw materials,some advantages have been achieved,such as mild conditions,less waste and low-cost.In this method,aniline was chosen as starting reactant,after diazotization,rearrangement,synthesis intermediates which called amino azobenzene,then p-phenylenediamine was obtained through hydrogenation of amino azobenzene.In this paper,we investigated the multi-step reaction process conditions and the results are as follows:firstly,optimal reaction conditions for 1,3-diphenyltriazene:introducing the mixture of nitric oxide which volume ratio is 1:1 into the aniline for 4h,the reaction was kept at 40?,the mass fraction of 1,3-diphenyltriazene will reach to 20%-25%;secondly,optimal reaction conditions for amino azobenzene:reaction temperature was 80 ?,reaction time was 0.5h,1,3-diphenyltriazene aniline solution,the conversion rate of 1,3-diphenyltriazene was 97.29%,the mass ratio of p-amino azobenzene to o-amino azobenzene was 6:1;finally,optimal reaction conditions for the hydrogenation of azobenzene:add 10%of the total mass of the raney nickel catalyst for the first time,then 1%of the total mass of the raney nickel catalyst was added for the subsequent reactions.The reaction temperature was 80 ?,the reaction pressure was 3 MPa,the conversion rate of azobenzene was 100%,and producing 1kg p-phenylenediamine was only cost 23 g raney nickel catalyst.And the total yield of p-phenylenediamine could reach 75%,the purity of the target afforded 95%.In addition,in order to figure out the diazo reaction of nitrification theory and acid free conditions in coupling reaction,the nitric oxide absorption mechanism was discussed in this paper.Depending on the Aspen plus,the flow of material and energy was simulated as well.The results of the study had significance guiding meaning for further optimization of the process.Finally,the enlarge tests also conducted in this paper,the results were satisfied,it had provided a useful basis for the industrial production ofp-phenylenediamine.