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Selective Oxidation of Toluene Over Nanostructured Oxides

Author: YeShuang
Tutor: DingWeiPing
School: Nanjing University
Course: Physical and chemical
Keywords: toluene selective oxidation n-hexadecylphosphonic acid perovskiteoxide NHPI
CLC: O643.36
Type: Master's thesis
Year: 2013
Downloads: 51
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Abstract


The selective oxidation of hydrocarbons to corresponding oxygen-containing compounds like alcohols, aldehydes and carboxylic acids is a very important organic transformations, which is of great interest not only to fundamental research but also to fine chemical industry. Toluene, as a typical alkyl aromatic molecule, can be oxidized to benzyl alcohol, benzaldehyde, benzoic acid, and benzyl benzoate, which are all commercially important intermediates in chemistry. Presently, the principal industrial oxidation of toluene suffered from equipment corrosion and low selectivity as well as generation of environmentally hazardous waste. For economic and environmental reasons, the oxidation reaction should be performed under mild condition using molecular oxygen as oxidant and be free of any solvent or additives. In this thesis, we explore the catalytic performance of different oxides in the selective oxidation of toluene. The morphology and physicochemistry properties of catalysts before and after toluene oxidation are investigated by means of XRD, TEM, SEM, H2-TPR and FTIR. The main contents and results are summarized as following:Firstly, we prepared MnO2nanowires through a facile hydrothermal method. To improve their selectivity, we coated MnO2with n-hexadecylphosphonic acid (HDPA). When the HDPA-MnO2were used to catalyze the oxidation of toluene in liquid phase, the conversion of toluene reached3.7%, and the selectivity to benzaldehyde reached 59.3%, at reaction temperature453K and total pressure of1MPa using pure O2as oxidant.Secondly, a series of perovskite oxides were obtained by a sol-gel route followed by a heat treatment at973K5h in air. Through partial substitution of A and B ions by other metal ions, we regulated the state of manganese or iron in the perovskite. Catalytic activity tests showed that the conversion of toluene reached2.9%, and the selectivity to benzaldehyde reached38.7%when used LaMno.5Tio.5O3as catalyst.Thirdly, oxides/NHPI catalysts were introduced to the aerobic oxidation of toluene and investigated in details under different conditions. By comparison, LaMnO3/NHQI revealed a good catalytic activity giving3.8%conversion of toluene and selectivity for benzaldehyde rose to78.1%at reaction temperature393K.In conclusion, oxides/NHPI catalysts were found to be able to improve the activity of the oxide catalysts. Further studies of the reaction mechanism and extensive application of this catalytic system for the other hydrocarbon oxidation are underway.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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