Load Type Nano Au Catalytic Reduction Two Nitrobenzene Compounds

For a long time, gold was regarded as an "inert" noble metal without any catalytic activity. Since the discovery of gold catalysts can show excellent catalytic behavior for low temperature CO oxidation in the late1980’s by Haruta, the conception that gold has no catalytic activity was totally reversed. During the last decades, small gold particles showed excellent catalytic activity in various chemical reactions. Besides the use in oxidation reactions, gold catalysts can also be applied in hydrogenation reductions, such as hydrogenation of α,β-unsaturated aldehydes/ketones, unsaturated hydrocarbons and nitro compounds etc.Amines are one of the most important chemical raw materials and intermediates, wildly used in dyes, pigments, reagents, rubber, pharmaceuticals, pesticides, fine chemicals and many other areas. Amines are usually prepared by reducing the corresponding nitro compounds or nitroso compounds. The traditional production technology used in the nitro compounds reduction is stoichiometric reduction. This method is a simple and mature process, and it has been widely used in industry, which however does not meet the standard requirements for current green fine chemical synthesis because of the high energy consumption, low yield, the toxic iron sludge byproduct and some other environmental problems. Recently the catalytic hydrogenation method becoming popular, such as Raney Ni etc., it is friendly techno-logy for environment because the high quality, less wastes and easily post-processing, etc. But it is quite difficult to achieve selective reduction when the raw material contents more than one unsaturated groups, and it will cause the low yield and high separating costs. Therefore, the selective catalytic reduction of a nitro group among several reducible groups in the same molecule remains highly challenging, especially when there are two NO2groups in the same molecule.In the first part, the preparation methods of TiO2supported Au catalyst have been studied. Using the deposition-precipitation (DP) method, the influence by many parameters has been studied, such as the surface area, preparation conditions, real gold loading, calcination temperature and so on. Then the catalytic activity of the catalysts was studied in the reduction reaction of dinitro-compounds. In order to reduce the catalyst cost, we have tried to use Cu instead of Au to prepare bimetallic catalyst. The result showed that both TiO2-P25supported catalyst and TiO2-P90supported catalyst have high selectivity, but the catalytic activity of TiO2-P90supported Au catalyst is higher than the TiO2-P25supported catalyst. Further optimizing the calcination temperature of the catalyst at200℃,250℃,300℃,400℃,500℃, showed that the catalysts calcinated at200℃and250℃have high catalytic activity but low catalytic selectivity, when calcinated at400℃and500℃, catalyst showed high catalytic selectivity but low catalytic activity, only the catalysts calcinated at300℃have both highest catalytic selectivity and activity.Furthermore, the study of the reduction application was tested in selective hydrogenation of dinitro-compounds. In this paper, the hydrogenation of m-dinitro-benzene over Au/TiO2catalysts have been studied, the effects of the reaction conditions including H2pressure, reaction time and temperature were tested, the results showed that the H2pressure and the reaction temperature are both propor-tional to reaction rate, the reaction time is proportional to the conversion rate, but the reaction selectivity were lowered if the temperature is too high. Finally, under room temperature,3MPa H2pressure, m-nitroaniline converted completely, the selectivity to m-nitroaniline reached98%. In order to extend the applicability of the present catalytic system, selective hydrogenations of substituted dinitrobenzenes were studied, such as2,6-dinitrotoluene,1,4-dinitrobenzene,1,2-dinitrobenzene,3,4-dinitrotolu-ene. All of them over the Au/TiO2catalysts show high selectivity.Finally, in order to explore the industry application of the supported gold catalysts, in this paper the recycling and reusability of Au/TiO2catalyst have been preliminary studied and discussed.