Study On Catalytic Hydrogenation Of 2,4-Dinitrotoluene With Isopropanol As Hydrogen Source

Catalytic hydrogenation plays an important role in the transformation of fossil and biomass resources.Hydrogen is a flammable and explosive gas,which has serious safety risks in production,storage,transportation and use.How to use hydrogen source safely is a challenge to realize intrinsically safe chemical production.Liquid organic hydrogen is expected to replace conventional hydrogen in catalytic hydrogenation process at room temperature and low pressure.In particular,isopropanol,as a liquid organic hydrogen source,not only meets the requirements of high hydrogen content,low cost,but also can be recycled.2,4-Diaminotoluene（2,4-TDA）is an important raw material in the polyurethane industry.The current industrial production method is the gas-liquid-solid three-phase catalytic reaction process using hydrogen directly,which has problems such as high safety risks and uneven mixing of reactants.The catalytic hydrogenation of2,4-dinitrotoluene（2,4-DNT）is used for the green production of polyurethane.Herein,a liquid-solid reaction of 2,4-DNT hydrogenation with isopropanol as hydrogen source was proposed.（1）Isopropanol dehydrogenation catalyst and its reaction performance were studied in batch reactor.Using Ru,Rh,Pt,Pd as active components and AC,γ-Al₂O₃,Zr O₂,Mg O,Si O₂ as supports,a series of supported monometallic and bimetallic catalysts were prepared.It was found that Ru5-Pt0.8/AC catalyst had the highest dehydrogenation activity of isopropanol.The dehydrogenation conditions were optimized and the yield of acetone was11.3%at 140℃for 3 h.XRD,TEM,BET,XPS characterizations of the catalyst showed that the active metals Ru and Pt were highly dispersed on the surface of the activated carbon carrier,and the metal particle size was about 2 nm.（2）The catalytic hydrogenation of 2,4-dinitrotoluene using isopropanol as hydrogen source and its performance were studied.Using Ru5-Pt0.8/AC bimetallic catalyst with which has good dehydrogenation effect of isopropanol in this reaction to investigated the hydrogenation reaction conditions.Under the conditions of 0.6 mass ratio of catalyst to2,4-dinitrotoluene,60 m L isopropanol/g_2,4-DNT and 35 m L water/g_2,4-DNT,the highest yield of 2,4-diaminotoluene was 99.2%at 135℃for 3 h.（3）The hydrogenation process of 2,4-dinitrotoluene with isopropanol as hydrogen source was studied.The nitro hydrogenation of benzene ring is carried out step by step to produce monoamino and diaminotoluene sequentially.Because of steric hindrance,the nitro group in the opposite position of methyl group hydrogenate more easily.Water plays an important role in the reaction process,which can activate nitro group through hydrogen bond,and then promote the hydrogenation of nitro group.（4）The intrinsic reaction kinetics of the hydrogenation of 2,4-dinitrotoluene over Ru5-Pt0.8/AC catalyst with isopropanol as hydrogen source and solvent were studied.The hydrogenation reaction rate models were established,and the calculated results were in good agreement with the predicted results.