| Based on the redox reaction between KMnO<sub>4 and ascorbic acid, a facile hydrothermal method has been developed to synthesize single-crystalα-MnO<sub>2,β-MnO2,γ-MnOOH nanorods, and Mn3O4 nanoparticles, respectively. It is found that this versatile synthesis route is novel and practical. XRD and TEM techniques are used to characterize the as-prepared products. Experiments indicate that the molar ratio of KMnO4 to ascorbic acid, pH value, reaction temperature and reaction time are the key factors to determine the crystallographic forms of as-prepared products.The catalytic activities of the as-prepared nanostructured manganese oxides includingα-MnO2,β-MnO2,γ-MnOOH nanorods and Mn3O4 nanoparticles, as well as commercial MnO<sub>2 are evaluated by monitoring the degradation of fuchsin acid in the presence of H2O2. The experimental results show thatβ-MnO2 nanorods has the highest activity among them and allows the decoloration degree of the fuchsin acid solution to reach 97.6% within 60 minutes. The kinetic study shows that the degradation process of fuchsin acid obeys rA = 333.3×cA1.76.Based on the reactive distillation technology, the as-prepared nanostructured manganese oxides are also used to catalyze the esterification reaction between acetic acid and isoamyl alcohol to synthesize isoamyl acetate. IR and GC tests are used to characterize the obtained products. The experiment results show thatβ-MnO2 nanorods has the best catalytic performce among the manganese oxides. The effects of various reaction parameters including the dosage of the catalyst, the molar ratio of acetic acid to isoamyl alcohol and the reaction temperature are investigated. The esterification ratio reaches 88.78% under the optimum conditions: molar ratio of acid/alcohol of 1.5, catalyst loading 0.2%(w/w) (i.e., weight of catalyst/total weight of reactants), reaction time of 210 minute. The kinetics of the esterification process and the mechanism of the catalytic process are also discussed.
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