The Study Of Solid Sulfonic Acid-Catalyzed Oxidation Of Aldehydes To Carboxylic Acids Using H₂O₂ As Oxidant

The transformation of aldehydes to carboxylic acids is an important reaction in organic synthesis and fine chemical industry. This thesis studied the oxidation of aldehydes to carboxylic acids using H2O2 as oxidant catalyzed by solid sulfonic acid. This catalytic oxidation system could efficiently transform aldehydes to carboxylic under mild conditions, and the catalyst is recyclable.Firstly the oxidation of benzaldehyde to the benzoic acid catalyzed by sulfonic acid resin Amberlyst 15 using 30% H2O2 as the oxidant was investigated. The conversion of benzaldehyde reached 85% under 90℃for 7 h using 5 wt% Amberlyst 15 and 1.5 equiv H2O2. And the yield of benzoic acid was improved to 95% when acetic acid was used as the solvent. The catalytic system also showed good catalytic activity in the oxidation of other aldehydes. Benzaldehyde derivatives with electron-withdrawing group and aliphatic aldehydes were almost quantitatively converted into their corresponding acids. Amberlyst 15 was an efficient, recyclable heterogeneous catalyst for the oxidation of benzaldehyde to benzoic acid by H2O2, which can be recycled for two times and the activity of the catalyst only decreased a little in the third run. But the mechanical strength of Amberlyst 15 was not high and easy to break into small particles.The more stable solid catalyst-sulphonated carbon materials were prepared. The influence of raw material for carbon and the sulphonated temperature were investigated. It was found that when starch was used as the raw material and the sulphonated temperature was 150℃, the sulphonated carbon materials showed the best catalytic activity and the amount of -SO3H was 1.0 mmol/g. The sulphonated carbon materials can be recycled. The catalytic activity slightly decreased when the catalyst was used for once, then the activity almost unchanged in the following two runs. The catalytic system can also catalyze oxidation of various aldehydes. However, the activity was lower than Amberlyst 15 which maybe result from the amount of-SO3H of sulphonated carbon materials was lower than that of Amberlyst 15.