Green Hydrogenation Synthesis Of L-2-aminobutanol Catalyzed By Ruthenium Carbon

L-2-aminobutanol is an important pharmaceutical intermediate,which is mainly used in the synthesis of ethambutol for treating tuberculosis.At present,the synthesis methods of L-2-aminobutanol are mainly divided into two categories:chemical resolution method and reduction method.The direct catalytic hydrogenation has the advantages of simple technology process,green and low production cost,good prospects for industrial application.In this paper,L-2-aminobutyric acid was used as the raw material,and Ru/C as the catalyst,sulfuric acid as an acidic additive,L-2-aminobutanol was synthesized by directly catalyzing hydrogenation from L-2-aminobutyric acid under certain temperature and pressure.The effect of various catalyst preparation methods and reaction conditions was explored.First the effect of sulfuric acid additive amount,reaction temperature,hydrogenation pressure and reaction time on the hydrogenation of L-2-aminobutyric acid was investigated.The optimal conditions are 4.0 g raw material,1.0 g Ru/C catalyst,200 mL deionized water,2.05 g sulfuric acid,100?,7 MPa pressure,12 h.The conversion rate was increased with the increase of sulfuric acid additive amount,but the product selectivity decreased slightly.Temperature had a great influence on the reaction rate and the selectivity of the product.When the temperature was higher than 100?,the reaction rate was obviously accelerated,but the selectivity and ee value decreased obviously.Under the pressure of 3-8MPa,the reaction rate was increased with the increase of pressure.In the preparation methods of Ru/C catalyst,the catalytic effect of the catalyst prepared by the gas phase hydrogen reduction method was better than that of the liquid phase reduction method.Under the above conditions,the conversion of 98.51%and 94.34%respectively was achieved.However,the addition of metal additives W,V,Ti,Rh and Pt did not significantly improve the activity of the catalyst.Finally,the stability evaluation of Ru/C catalyst prepared by gas phase reduction method and liquid phase reduction method was carried out.In the gas phase reduction method,the activity of Ru/C catalyst was decreased gradually after recycling 10 times,the conversion of raw material was decreased from 98.51%to about 80%.Through the analysis of the characterization of N₂ physical adsorption,SEM,XRD,TEM and XRF,it was revealed that the adsorption of organic salt on the surface of activated carbon which covered the activity center of surface Ru and the loss of active component resulted in the decreased activity of Ru/C catalyst.After the improvement of the washing and drying methods of liquid phase reduction,the activity stability of the catalyst was improved,and the conversion of raw material remained above 95%after recycling 8 times.