Selective Catalytic Hydrogenation Of Functionalized Nitroarenes

Functionalized anilines are important substrates for pharmaceuticals, herbicides, pigments, and other fine chemicals.The catalytic hydrogenation of aromatic nitro compounds is a well-known and establishd method for the large-scale industrial manufacture of aromatic amines, key intermediates in the synthesis of a wide of variety fine chemicals. The hydrogenation of simple nitro compounds is unchallenged and commercially available catalysts can be used. But when other reducible groups are present in the same molecule, it is difficult to reduce the nitro group selectivity in a catalytic process.In this thesis, the Pt-Sb/TiO2 bimetallic catalyst was prepared by successive impregnation method, which is used for 3-nitrostyrene (NS) selective hydrogenation of 3-aminostyrene (AS). The catalytic performance of Pt-Sb/TiO2 in different reaction medium such as water, alcohol, heptane and scCO2 has been discussed. It was found that Pt-Sb/TiO2 catalyst show the best catalytic performance in the water. Hydrogenation of NS to AS over 0.5% Pt-2.24% Sb/TiO2 catalyst, when NS conversion rate is close to 100%, the selectivity of AS is 98.2%, continue to extend the reaction time of 3 h, and the selectivity of AS is still 98%, indicating that the bimetallic catalyst can inhibit vinyl hydrogenation. Moreover, the hydrogenation rate of NS could be elevated by 10 times by increasing reaction temperature from 50 ℃ to 120 ℃, the selectivity of AS is 96%, indicating that the catalyst at high temperature reaction also exhibited excellent catalytic performance. In addition, we show their scope and limitations for the preparation of aromatic amino compounds substituted with functional groups such as C-X、C=N and CHO, Pt-Sb/TiO2 catalyst showed satisfied catalytic activity and selectivity to the target product.The Pt-Sb/TiO2 catalyst was investigated in detail by means of XPS, XRD, TEM, H2-TPR. The Pt particles with size in a range 1.8-2.9 nm are observed, the bimetallic catalyst surface in the presence of hydrogen spillover effect, the catalyst surface may exist electron transfer between Pt and Sb or Sb2O3, the Ar+ ion sputtering experiment shows that surface enrichment withTi species and bulk enrichment with Pt species.The Pt/ATO catalyst was prepared by modified impregnation method (ATO:antimony doped tin oxide) used in hydrogenation of 4-nitrophenyacetylene (NPA). Found that the selectivity to 4-aminoacetophenone(AAP) above 88.9% at 100% conversion in water.