Wet Oxidation of Phenol on Ce1−xCuxO2−δCatalyst☆
Wet Oxidation of Phenol on Ce1−xCuxO2−δCatalyst☆
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DOI：
10.1006/jcat.1999.2422
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发表时间：
1999-05
影响因子：
7.3
通讯作者：
S. Hocevar;J. Batista;J. Levec
中科院分区：
文献类型：
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作者：
S. Hocevar;J. Batista;J. Levec
采用共沉淀法合成了Ce 1 − xCuxO 2 −δ（0.05<x<0.20）催化剂，用于水溶液中苯酚的湿式催化氧化。三个最重要的合成参数，混合金属盐溶液的浓度，共沉淀剂的添加速率和共沉淀过程中的搅拌器速度，进行了优化与中心复合设计使用的催化活性作为响应函数。催化活性强烈依赖于共沉淀过程中的搅拌速度。氧化铜和二氧化铈的高度相互分散（具有约9 nm的平均微晶尺寸）增强了固溶体的形成。当催化剂中铜的总浓度增加时，二氧化铈的晶胞参数减小，最可能遵守Vegard定律。该催化剂被证明在低pH值的水热反应条件下非常稳定。在半间歇式CST反应器中反应5小时后，从在高于1033 K的空气流中煅烧2小时的催化剂样品中浸出小于100 ppm的Cu，并且在催化剂表面上仅形成非常少量的碳质沉积物（0.6重量%）。苯酚降解的动力学可以解释由一个方程有效的均相自催化反应，其中的速率常数线性依赖于非均相催化剂（铜）的浓度。这表明该反应通过非均相-均相自由基-支链机理进行。
Ce1−xCuxO2−δcatalysts with 0.05<x<0.20 for catalytic wet oxidation of phenol in aqueous solutions have been synthesised using the coprecipitation method. The three most important synthesis parameters, the concentration of the mixed metal salt solution, the rate of coprecipitant addition and the stirrer speed during coprecipitation, were optimised with central composite design using the catalytic activity as a response function. The catalytic activity strongly depends on stirrer speed during coprecipitation. A high mutual dispersion of copper oxide and ceria, having the average crystallite size of about 9 nm, enhances solid solution formation. The unit cell parameter of ceria decreases when the overall concentration of copper in the catalyst increases, most probably obeying Vegard's law. The catalysts proved to be very stable in hydrothermal reaction conditions at low pH values. After 5 h of reaction in the semibatch CST reactor less than 100 ppm of Cu was leached out of catalyst samples that were calcined in a flow of air for 2 h above 1033 K, and only a very low quantity of carbonaceous deposits were formed on the surface of the catalysts (0.6 wt%). The kinetics of phenol degradation could be interpreted by an equation valid for homogeneous autocatalytic reactions, in which the rate constant depends linearly on the heterogeneous catalyst (Cu) concentration. This demonstrates that the reaction proceeds through a heterogeneous–homogeneous radical-branched chain mechanism.