Study On Continuous Hydrogenation Of Nitroarene Sulfonic Acid

Sodium m-aminobenzenesulfonate is an important chemical intermediate,mainly used as a synthetic dye.At present,the metal reduction method and catalytic hydrogenation method are mostly used in the industry,and the metal reduction method has been gradually eliminated.The catalytic hydrogenation method has become a current research hotspot because of its clean process.The precious metal catalysts on the market are expensive,have a low lifespan,and have poor activity..And the method is easy to cause the deactivation of noble metal catalysts,and there is no clear solution for the deactivated catalysts.In this project,different commercial catalysts were screened,and two catalysts,5% Pd/C and 0.5% Pt/C,were synthesized for the hydrogenation of nitroaromatic sulfonic acid,and they were applied to batch reactors,continuous reactors,in a microchannel continuous reactor.But the catalyst still has obvious deactivation phenomenon,the substance poisoning the catalyst was finally determined through the experiment,and the catalyst regeneration was carried out.The research contents are as follows:(1)First,the reaction process was screened by batch method,and different catalyst types,temperature,pressure,reactant concentration,stirring rate,and catalyst proportion were screened.The optimal reaction conditions were finally determined as follows: the temperature is 90 ℃,the pressure is 1.5 MPa,the stirring rate is 1000 r/min,and the catalyst ratio is 2.5%.Secondly,the 0.5%Pt/C catalyst was scaled up twice and showed good stability.And 0.5%Pt/C is more suitable for scale-up due to its high activity and low cost.;(2)The stability verification experiment of different reactors was carried out using the self-made catalyst.The catalyst could be applied 6 times for the reaction using the batch tank reactor,and the yield could reach 96%;the continuous tank reactor was used for 25 hours of continuous operation.The yield is stable above 99%;the experimental continuous flow microchannel reactor runs continuously for 9 hours,the yield is stable above 98%,and the problem of catalyst deactivation still exists;(3)The deactivated catalyst was characterized and analyzed.The reason for the deactivation was: organic matter blocked the catalyst pores,resulting in the inability of the active sites to contact the reactants.It was analyzed that the organic substance blocking the catalyst pores was 3,3’-dinitrodiphenyl sulfone,but this substance did not cause catalyst deactivation,and its hydrogenation product was the main cause of catalyst deactivation.By washing with ethanol,the catalyst can be regenerated to restore its activity to about 80%.(4)Activated carbon adsorption on the raw material can remove some toxins and slow down the deactivation rate of the catalyst.The characterization results show that the specific surface area of the activated carbon after adsorption is greatly reduced,which verifies the inference.