Synthesis Of 4,6-Diaminoresorcinol Dihydrochloride

As the "super fiber" of the 21st century,Poly-p-phenylene benzobisoxazole?PBO?not only had high strength and high modulus performance,but also had extraordinary high temperature resistance and flame retardancy.It could be used in aerospace and military defense.The synthesis process of 4,6-diaminoresorcinol?DAR?,the key intermediate of PBO fiber,was important.Based on a large number of literatures,the high purity 4,6-dinitroresorcinol was synthesized by one-pot reaction via sulfonation,nitration and hydrolysis.Then,4,6-dinitroresorcinol was hydrogenated to 4,6-diaminoresorcinol.Low-cost Raney nickel was used as the catalyst and could be reused,which was cheaper than Pd/C.The microreactor was applied to the nitration reaction,which greatly reduced the risk of the experiment and was beneficial to industrial production.The dissertation was mainly divided into three parts:Part ?:4,6-Dinitroresorcinol was synthesized by a one-pot reaction of sulfonation,nitration and hydrolysis in a batch reactor.Then it was refined to 99%HPLC content.After optimizing of the type and amount of sulfonating agent,sulfonation temperature,amount of nitration agent,nitration temperature,nitration time,hydrolysis temperature and water dosage,the optimal reaction conditions were as follows.Sulfonation reaction:amount of resorcinol 11.0 g,amount of 105 fuming sulfuric acid 110 g,sulfonation temperature 60?,sulfonation time 2 h.Nitration reaction:amount of 65%nitric acid 19.0 g?molar ratio with resorcinol=2:1?,nitration temperature 20³0?,and nitration time 1 h.Hydrolysis reaction:amount of water 154.0 g,hydrolysis temperature 100?,and hydrolysis time 12 h.In the refining step,the raw product was stirred with 200 mL of hot water for 30 min,and then filtered.Thus,a high purity of bright yellow product 4,6-dinitroresorcinol was obtained,The total yield was 71.9%.Part ?:Microreactor was used in the nitration reaction to synthesize4,6-dinitroresorcinol.Due to the requirements of the use of the microreactor,we first used a batch reactor to perform the sulfonation reaction,then used the microreactor to perform the nitration reaction,and finally performed the hydrolysis reaction in a batch reactor.In order to meet the requirements of the microreactor,the reaction conditions of the sulfonation reaction were changed.After optimizing the flow rate,residence time and reactant ratio,an optimal condition?microreactor?was obtained.Sulfonation reaction?batch reactor?:55.0 g of resorcinol in 200 mL of acetic acid,amount of 105fuming sulfuric acid 650 g,sulfonation temperature 60?,sulfonation time 2 h.Nitration reaction?microreactor?:total flow rate 5.6 mL/min,residence time 1.5 min,HNO₃:RS?molar ratio?2.2:1.Hydrolysis reaction?batch reactor?:amount of water154.0 g,hydrolysis temperature 100?,hydrolysis time 12 h.In the refining step,the raw product was stirred with 200 mL of hot water for 30 min,and then filtered.Thus,a high purity of bright yellow product 4,6-dinitroresorcinol was obtained,and the total isolated yield was 70.1%.Part ?:Low-cost Raney nickel was used as the catalyst to synthesize4,6-diaminoresorcinol from 4,6-dinitroresorcinol.The optimal conditions were:N,N-dimethylformamide as solvent,0.13 mol/L of the DNR concentration,the mass ratio of Raney nickel catalyst to DNR 0.4:1,hydrogen pressure 1.0 MPa,reaction temperature 120?,and stirring speed 400 rpm.After catalytic hydrogenation and work-up,78.1%yield of DAR.2HCl was obtained.The catalyst Raney nickel could be reused eight times,and the HPLC content of the product was higher then 90.1%.