Electrolytic reduction of CCl4 -: effects of cathode Material and potential on kinetics, selectivity, and product stoichiometry
Electrolytic reduction of CCl4 -: effects of cathode Material and potential on kinetics, selectivity, and product stoichiometry
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DOI：
10.1089/ees.1999.16.1
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发表时间：
1999-01-01
影响因子：
1.8
通讯作者：
Festa, KD
中科院分区：
文献类型：
--
作者：
Liu, ZH;Arnold, RG;Festa, KD
四氯化碳（CCl 4）在由纯Ag、Al、Au、Cu、Fe、Ni、Pd和Zn组成的金属阴极上通过电解还原转化。主要产物为CHCl 3、CH 2Cl 2和CH 4。在顶空样品中还观察到痕量CH 3Cl、C2 H4、C2 H6、C3 H8和其他未鉴别产物。在相同的实验条件下，CHCl 3被还原为CH 2Cl 2和CH 4，尽管速率较慢。CH 2Cl 2在这些实验过程中基本稳定（k（s）< 0.05 L/m（2））。min）。CCl 4还原是本体液相浓度的第一顺序。伪一级速率常数是阴极材料、pH和施加的阴极电势（E-c）的函数，其范围为小于或等于E-c的-1.4V至小于或等于-0.4V vs. SHE。在所有的电极，反应速率符合Butler-Volmer动力学，修改为考虑传质限制。在可比条件下，在Ni和Cu电极上的CCl 4电解动力学上级使用任何其他金属测试的转化动力学。在E-c = -0.6和-0.8 V下，CCl 4在Cu电极上的还原速率常数随着pH的增加而降低，范围为2 < pH < 6。在E-c小于或等于-1.2V时，还原受向电极表面的传质限制，与阴极材料和pH无关。（脱卤速率与总电解电流的比率）与用于产生氢气的材料依赖性交换电流密度成反比，表明H-2（g）的产生是实验条件下最显著的竞争反应。基于效率考虑，电极材料的顺序为Zn > Cu > Fe > Ni。
Carbon tetrachloride (CCl4) was reductively transformed via electrolysis at metal cathodes consisting of pure Ag, Al, Au, Cu, Fe, Ni, Pd, and Zn. Primary products included CHCl3, CH2Cl2 and CH4. Traces of CH3Cl, C2H4, C2H6, C3H8, and other unidentified products were also observed in headspace samples. CHCl3 was reduced to CH2Cl2 and CH4 under the same experimental conditions, although at a slower rate. CH2Cl2 was essentially stable during the course of these experiments (k(s) < 0.05 L/m(2) . min). CCl4 reduction was first order in the bulk liquid phase concentration. Pseudo-first-order rate constants were a function of cathode material, pH, and applied cathode potential (E-c) in the range -1.4 V less than or equal to E-c less than or equal to -0.4 V vs. SHE. At all electrodes, reaction rates conformed to Butler-Volmer kinetics, modified to account for mass transfer limitations. Under comparable conditions, the kinetics of CCl4 electrolysis at Ni and Cu electrodes were superior to those of transformation using any other metal tested. At E-c = -0.6 and -0.8 V, rate constants for CCl4 reduction at a Cu electrode decreased with increasing pH in the range 2 < pH < 6. At E-c less than or equal to -1.2 V, reduction was limited by mass transfer to the electrode surface and was independent of cathode material and pH, Electrode efficiency (ratio of dehalogenation rate to total electrolytic current) for CCl4 reduction was inversely related to the material-dependent exchange current density for hydrogen gas generation, suggesting that production of H-2 (g) is the most significant competitive reaction under the conditions of the experiments. Based on efficiency considerations, the electrode materials were ordered Zn > Cu > Fe > Ni.