Modification Of So <sub> 4 </ Sub> <sup> 2 - </ Sup> / Fe <sub> 2 </ Sub> O <sub> 3 </ Sub> Solid Acid Preparation And Catalytic Properties Of

Solid acid of SO₄^2-7M_xO_y type, widely used as a good green catalyst because of its advantages in good catalytic activity, wide useage, easy to be separated from reaction mixture, little corrosive to reactor, friendly to environment, reutilization and meeting the demand of green catalyst, has become one of the hot spots in the catalyst area.At present, many researches about solid super acid have been made. Solid super acid of SO₄^2-/ZrO₂ and SO₄^2-/SnO₂ type have attracted much attention for its strong acidity and good performance in catalyzing organic synthesis reaction, while fewer reports on modification and application of SO₄^2-/Fe₂O₃ have been made. Solid super acid catalyst composed of iron oxide as active component has obvious advantages in its simple preparation procedure, good catalytic activity, especialilly much cheaper in comparison with catalysts prepared by other metal oxides such as titanic oxide and zirconia, it's worthy of industrialized investigation for these reasons. A series of modified S₄^2-/Fe₂O₃ solid acid catalysts were prepared and were applied in the study of alkoxylation of phenol and nitration of toluene. It could provide the further exploration and application of this type of solid acid catalyst with some referrence value. Research presented in this paper consists of following aspects:1. Research on methoxylation of phenol over the modified catalystA batch of SO₄^2-/Fe₂O₃-MoO₃ catalysts was prepared through processes such as aging, filtration, washing, desiccation, immerging, and calcination. Their acid site structure, crystalline structure, morphology, element valence were characterized by IR, XRD, SEM, XPS, respectively, and their activity had been evaluated by methoxylation result. Effect of Reaction time and different modified catalyst on the reaction had been recorded by UV-Vis, the analysis result turned out to be in line with result detected by GC-MS. Experiment result showed the feasibility of applying the SO₄^2-/Fe₂O₃-MoO₃ catalyst in the methoxylation of phenol at room temperature. Catalytic capacity of modified SO₄^2-/Fe₂O₃ catalyst increased with the addition amout of MoO₃ in this study. To some extent, modification of catalyst was effective from the point of its catalytic result, especially when MoO₃ account for 16 mol% in catalyst, conversion of phenol and selectivity of methoxyphenols achieved up to 70.5% and 80%, especially. However, the catalysis efficiency is still low, so it is necessary to further improve catalyst and experiment condition. In addition, a possible mechanism of product formation has been proposed on basis of literature. 2. Research on nitration of toluene over the modified catalystA series of different metal oxides modified SO₄^2-/Fe)2O₃ catalysts were prepared according to the method mentioned above and also coprecipitation method. FT-IR was used to analyze three main factors which affected catalyst acidity during preparation: sulfur acid concentration, calcination temperature and modifier. It was also available to study the catalyst after absorption of pyridine. An investigation about the effect of reaction condition such as reaction time, molar ratio of reactants, different modifier and amount of catalyst on nitration was carried on by UV-Vis and GC-MS in this part, resulted in concluding an appropriate reaction condition. Experiment result tured out that sulfur acid concentration should be 0.5 mol/L and calcination temperature should be 823 K. Product yield was found to associate with catalyst acid strength, which increased with the increase acidity sites of catalyst. Modified catalysts improved the product yield and selectivity to p-nitrotoluene differently. SO₄^2-/Fe₂O₃-PbO prepared by coprecipitation method gained relatively more acidity sites than other catalysts, but displayed low selectivity to p-nitrotoluene. Meanwhile, SO₄^2-/Fe₂O₃-MoO₃ upgraded the nitrotoluenes yield to 83.2% and reduced mass ratio of o-nitrotoluene and p-nitrotoluene to 1.24.