Study On The Preparation Of Aromatic Amines By Liquid Catalytic Hydrogenation

Aromatic amines are widely used in dyestuffs, pharmaceutical products, agricultural chemicals, surfactants. And most of the aromatic amines come from corresponding nitro compounds. Reducing the nitroarene to aromatic amines is an important reaction in the production of fine chemical. There are many methods of reducing nitro to amine, such as the Bechamp reduction employed iron, electrolysis reduction, catalytic hydrogenation and so on. Bechamp reduction brought out serious pollution to environment, and it should be replaced by other means someday. Electrolysis reduction cannot be brought into practice because of higher cost. Catalytic hydrogenation, especially liquid catalytic hydrogenation, relieves pollution for environment greatly and promotes the production quality. With the increasing attention to environment problems, popularizing the catalytic hydrogenation technology in the industry production must bring prominent economic and social benefits.With the development of science, the study for catalytic hydrogenation has been pushed continuously. This paper summarizes the catalytic hydrogenation development in recent years.This dissertation studied the appliance of liquid catalytic hydrogenation technology to the production of procaine and butyl-4-aminobenzoate. For preparing procaine by liquid catalytic hydrogenation technology, Pd/C catalyst and the Raney-Ni catalysts which are prepared by different sizes Ni-Al alloys with the special methods, were studied. From the view of degrading the cost in the industry production, a special type of Raney Ni catalyst was chosen for the preparation of procaine. By catalytic hydrogenation instead of iron reduction, 4-nitrobenzoic acid -2-(diethylamino)ethyl ester is reduced to 4-aminebenzoic acid-2-(diethylamino)ethyl ester. The influence of the temperature, pressure, catalyst dosage and reaction time to yield were discussed, and the optimized technology was as follows: temperature 130, hydrogen pressure 3.0MPa, time 7 h. The conversion rate was 95%. The yieldof procaine was 83.5%, The purity is up to 98.02%.The catalytic hydrogenation applied to the preparation of procaine simplified the purification step and overcame the drawbacks such as serious pollution, inferior product and heavy work.In this dissertation the preparation of butyl-4-aminobenzoate from butyl-4-nitrobenzoate with catalytic hydrogenation was also studied. The influence of the temperature, pressure, catalyst dosage and reaction time to yield were discussed.The optimized technology was as follows: temperature 90癈, hydrogen pressure 2.5MPa. The conversion rate was 99%. The yield of butyl-4-aminobenzoate was 75.4%, The purity is up to 95.6%.And in the latter of this paper, the production of p-amine benzoic acid from p-nitro benzoic acid was also studied.