Liquid Catalytic Hydrogenation Of Three Aromatic Nitro Compounds Over Rapidly Quenched Skeletal Nickel

Aromatic amines are very important organic intermediates. They are widely used in dyestuffs, pharmaceuticals, agricultural chemicals, additives and surfactants. Most of the aromatic amines come from corresponding nitro compounds. Reducing the nitroarene to aromatic amines is an important reaction. Catalytic hydrogenation, especially liquid catalytic hydrogenation, greatly decreases environmental pollution and promotes the quality of products. With the increasing attention to environment problems, popularizing catalytic hydrogenation technology in the chemical industry will undoubtedly bring prominent economic and social benefits. So it is in urgent need of developing more efficient catalyst and replacing traditional methods with catalytic hydrogenation.In this thesis, we develop the rapidly quenched skeletal Ni catalyst and addition of molybdenum. Its characterizations are carried out with XRD and SEM. Rapidly quenched skeletal Ni is a new kind of skeletal nickel prepared by rapid quenching technique. Their activity, selectivity and thermal stability are tested in the preparation of two dye intermediates of aromatic amines by liquid catalytic hydrogenation.This thesis studied the appliance of the rapidly quenched skeletal Ni catalyst in the liquid catalytic hydrogenation of p-nitroacetanilide (p-NAT) to p-aminoacetanilide (p-AAT). Under the optimized conditions (60℃, 1.0 MPa, w(cat.)/m(p-NAT)=1/10 and methanol as solvent), 99.5% selectivity of p-AAT with 100% p-NAT conversion was obtained in 24 minutes. The apparent activation energy of the reaction is about 34 kJ/mol. It can be concluded that the rapidly quenched skeletal Ni catalyst shows higher activity and selectivity in the hydrogenation of p-NAT.In order to expand the use area of the rapidly quenched skeletal Ni catalyst and to test its catalytic performance further, it was also used in the preparation of 3-amino-4-methoxyacetanilide (AMA) from 3-nitro-4-methoxyacetanilide (NMA). The effects of reaction conditions such as different solvents, the amount of catalyst, reaction temperature and pressure were studied and all of them were optimized to serve for industrial application. Under optimized conditions (60℃, 1.0 MPa, m(cat.)/m(NMA)=1/10 and methanol as solvent), the conversion of NMA was 100% and the selectivity of AMA was as high as 99.9% in 40 minutes. The apparent activation energy of the reaction is about 52 kJ/mol. The catalyst was repeatedly used for 44 times and exhibited excellent catalytic activity and stability.Moreover, the reaction mechanism of liquid hydrogenation of 3-mononitrophenyl -β-hydroxyethyl sulfone to 3-aminophenyl-β-hydroxyethyl sulfone was studied. Based on the experimental observations by HPLC, a possible mechanism about the reaction catalyzed by the skeletal nickel catalyst was proposed.