Preparation Of L-2-Aminobutanol By Catalytic Hydrogenation Of L-2-Aminobutyric Acid With Ru/C Catalyst

L-2-aminobutanol as an important intermediate for anti-tuberculosis drugs ethambutol,has a huge market demand.The traditional synthetic route process is complicated,and causes heavily environmental pollution.In this paper,L-2-aminobutyric acid was used as raw material to synthesize L-2-aminobutanol directly by asymmetric catalytic hydrogenation,which effectively avoided the use of organic solvents and simplified the experimental process.The effects of reaction conditions on the yield,selectivity and optical purity of L-2-aminobutanol were summarized.The related factors influencing the activity of Ru/C catalyst were discussed.The effect of initial phosphoric acid concentration on the conversion of raw materials was investigated during the reaction of L-2-aminobutyric acid for the preparation of L-2-aminobutanol.In the range of 0~0.42 M phosphoric acid concentration,the conversion rate of L-2-aminobutyric acid increases with the increase of initial concentration of phosphoric acid.When the initial concentration of phosphoric acid is less than the concentration of L-2-aminobutyric acid,the raw material can not be completely converted.At this time,the maximum conversion rate of raw material is the ratio of phosphoric acid concentration to raw material concentration.By analyzing the concentration of raw material and product with the change of time in different temperature,it was confirmed that the reaction temperature has an important influence on the selectivity and optical purity of the product.The optimum reaction pressure was determined by the study of hydrogen pressure.The experiment also proved that hydrogen is one of the important reasons for the racemization of L-2-aminobutanol.The supported 5wt% Ru/C catalyst prepared by liquid phase reduction at room temperature under the condition of excess(solution)impregnation method.It was found that the catalyst reduced by formic acid has higher activity.The results of XRD,TEM and EDX showed that Ru particles in the catalyst were highly dispersed,the diameter was about 1nm,and the dispersion was distributed on the activated carbon supporter.After 13 hours of catalytic hydrogenation by 5wt%Ru/C at the raw material concentration of 0.39 M,phosphoric acid concentration of 0.42 M,100? and 1000 psi hydrogen pressure,the conversion of the raw material was 93.73%,the yield of the product was 92.99%,the selectivity was 99.21%.The optical purity of L-2-aminobutanol was more than 99%.The catalyst remains highly active in the above system after 20 times reuse,indicating that its stability is satisfactory.