对甲基苯酚在不同催化剂电极上的电氧化

在无隔膜电解槽中, 利用线性伏安法和恒电流电解法研究了Ti/PbO2、石墨和Pt电极对于对甲基苯酚电氧化的催化活性, 通过电解前后溶液中对甲基苯酚及其氧化中间产物的液相色谱测定, 比较了对甲基苯酚在3种电极上的转化和降解速度, 并讨论了对甲基苯酚电氧化降解的历程和速控步骤. 研究结果表明, Ti/PbO2电极能有效地催化氧化水溶液中的对甲基苯酚, 并将其彻底去除, 电极活性较高; 石墨电极也能够催化氧化水溶液中的对甲基苯酚, 但效果较差; Pt电极在3.0 h的电解时间内, 只能将对甲基苯酚转化成对苯二酚, 而不能将其完全矿化. 对甲基苯酚电氧化降解需要经过对羟基苯甲醇→对羟基苯甲醛→对羟基苯甲酸→对苯二酚→对苯醌→顺丁烯二酸→草酸, 最终生成二氧化碳和水的历程. 当以Ti/PbO2作阳极时, 对苯二酚转化为对苯醌和顺丁烯二酸转化为草酸两步反应为较慢的速控步骤; 当以石墨作为阳极时, 对苯二酚转化为对苯醌的反应为速控步骤.

Electrooxidation of p-Methylphenol at Different Catalyst Electrodes

The electrocatalytic activity of Ti/PbO2, graphite and platinum electrodes for the electrooxidation of p-methylphenol was studied by linear sweeping voltammetry and galvanostatic electrolysis in an electrolytic cell without diaphragm. The conversion, degradation rate, reaction mechanism and rate determining steps of p-methylphenol at the three kinds of electrodes were explored by determinations of p-methylphenol and intermediates in the electrolyte before and after electrolysis. The experimental results indicate that Ti/PbO2 electrode with a high activity can effectively oxidize and remove p-methylphenol; graphite electrode can also oxidize p-methylphenol, but its removal ability was poor; platinum electrode can only oxidize p-methylphenol to hydroquinone in the electrolytic time of 3 h; p-methylphenol can not be oxidized completely. The mechanism of the electrooxidation degradation of p-methylphenol may be p-methylphenol→p-hydroxy-benmethanol→p-hydroxybenzaldehyde→p-hydroxybenzoic acid→hydroquinone→benzoquinone→maleic acid→oxalic acid, and the final product is CO2. The electrooxidation reactions of hydroquinone and maleic acid are the rate determining steps for Ti/PbO2 electrode, while the electrooxidation reaction of hydroquinone is a rate determining step for graphite electrode.