| Aminophenol is a widely used organic chemicals as medical,dyes intermediates.Methods for preparing p-Nitrophenol are many,such as iron powder reduction of PNP,catalytic hydrogenation,and NB electrolytic reduction method or the like.However,a variety of methods has its own drawbacks,such as iron reduction produced iron mud and more serious pollution impacting on the environment;the liquid phase hydrogena tion equipment investment and the high cost of raw materials;electrolytic reduction of NB method is demanding more stringent production control,high power consumption,and is not suitable for the power shortage to use.In the recent literature,it had a preliminary analysis of the reduction of aromatic nitro compounds by iron oxides/Fe(II)system in the anaerobic condition.The strength of reductive ability not only affected the rate of removal of contaminants,but affected the yield of the aromatic amine on the type of aromatic nitro compounds in the system of iron oxides/Fe(II).But because of anaerobic state requirements more stringent and the reaction of low concentration,it was not suitable for industrial production and the regulation of pH during the whole reaction processes.Therefore,the thesis established catalytic reduction of PNP as model by iron oxides/Fe(II)in the open system,and laid the foundation for the development aromatic amine low-cost preparation,self-catalytic synthesis of iron oxides and the degradation and restore of organic.The main research work and results are summarized as follows:(1)In the open system it studied catalytic reduction of PNP by Fe3O4/Fe(?),and at room temperature(T=293K),reaction factors such as pH,the concentration of PNP,adding speed,Fe3O4 dosage effected two sides of PNP reduction,there was a optimal usage,and pH was great on the reaction,research showed the neutral of pH reduction effect was best under the same conditions.Using FT-IR,UV-vis,HPLC etc instrument tracked reduction process of PNP by Fe3O4/Fe(?),and analysed of the changes and the rules of the matter.The results showed that:it was intermediate hydroxybenzotriazole hydroxylamine generating in the reaction process,and the total mass before and after the reaction was substantially conserved.(2)Three kinds of catalyst(called Fe3O4,?-FeOOH,?-Fe2O3)and Fe(?)system were catalytic reduction of PNP,it was compared and analyzed three kinds of iron oxides under the same conditions.The results showed Fe3O4/Fe(?))?-FeOOH/Fe(?)>?-Fe2O3/Fe(?),so the best was Fe3O4/Fe(?)system and it was reduction rate of 96%at room temperature.And the means of FT-IR,XRD,BET and SEM were used to characterize and compare the before and after reaction of iron oxides.The results showed that:it was the reaction process with ?-FeOOH generation.It compared the three specific surface area,and revealed the three there was a significant difference in microstructure.(3)It studied the influence of reaction temperature by the coexisting Fe3O4/Fe(?)of catalytic reduction PNP.The results showed that:the temperature elevated was conducive to the reaction,and was conducive to improve the conversion rate of PNP and the yield of PAP,PNP reaction rate was correspond to the Arrhenius equation with temperature,the activation energy for the reaction was 55.714kJ·mol-1.Catalytic Kinetic studies found that this photocatalytic comply with first-order reaction kinetics.(4)Iron oxides might be circular,the results showed that after four cycles of PNP conversion and PAP yield was still reached 100%,or used as a dye for sale.It was not only saving raw materials,but also reduced the cost.PAP was processed such as acidification,decolorization,refining and drying.And after crystallization of PAP characterization determination of FT-IR,1HNMR spectra,melting point determination and HPLC the purity of the obtained product was very high.(5)The mechanism of reduction of PNP by iron oxides/Fe2+ system was further study. |
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