【作者】 左鹏；

【导师】 于少明；

【作者基本信息】 合肥工业大学 ， 化学工艺， 2008， 硕士

【摘要】 水滑石（LDHs）及其焙烧后得到的复合氧化物是一类在催化、吸附等领域有着潜在应用的材料。本文以NaOH／Na₂CO₃为沉淀剂，采用共沉淀法合成了Cu-Ni-Al LDHs、Cu-Mg-Al LDHs、Fe-Ni-Al LDHs和Fe-Mg-Al LDHs，考察了它们在不同温度焙烧下得到的复合氧化物在催化湿式过氧化氢氧化法降解苯酚中的催化性能。结果表明在相同的实验条件下，只含铁的复合氧化物催化活性较差（苯酚转化率<10％），而含铜的复合氧化物，尤其是铜镍铝复合氧化物表现出较好的催化活性。少量Fe的引入有利于表面活性中心Cu的分散，本实验合成了铜镍铁铝复合氧化物；并以苯酚转化率为指标，确定了合成Cu-Ni-Fe-Al LDHs时各元素的适宜比例：∑M²⁺／∑M³⁺=3，Fe³⁺／∑M³⁺=0．25，Cu²⁺/ΣM²⁺=0．25；利用TG-DTA、XRD、FT-IR等表征手段研究了四元水滑石焙烧过程中的结构变化。通过单因素条件实验，确定了Cu-Ni-Fe-Al复合氧化物应用于含酚废水处理时(初始苯酚浓度400mg·L^-1的最佳工艺参数：催化剂浓度400mg·L^-1，M_H2O2／M_phenol（摩尔比）为12，反应温度60℃，不调节体系的初始pH值（=6．5），反应60min后，苯酚转化率达97．5％。Cu-Ni-Fe-Al复合氧化物具有良好的循环使用性，四次循环后，仍保持较高的苯酚转化率（93．5％）。本文还利用高效液相色谱对不同反应时间的苯酚降解产物进行了分析，检测到了对苯二酚、邻苯二酚、顺丁烯二酸等物质。推测其反应历程如下：苯酚在羟基自由基的进攻下，首先生成对苯二酚、邻苯二酚、对苯醌等芳香族物质，然后这些芳香族中间产物再进一步氧化开环，经过一系列步骤，生成顺（反）丁烯二酸；后者经羟基自由基的氧化，生成草酸、甲酸等小分子物质；而这些小分子物质，最终可矿化成为CO₂和H₂O。更多还原

【Abstract】 Layered double hydroxides （LDHs） and their derivatives, mixed oxides by calcining LDHs, are one of important potential materials in the catalysis and adsorption fields.In the thesis, Cu-Ni-Al LDHs, Cu-Mg-Al LDHs, Fe-Ni-Al LDHs and Fe-Mg-Al LDHs were prepared by coprecipitation, from the corresponding nitrate solutions and mixed precipitants （NaOH and Na₂CO₃）. Mixed oxides were obtained by calcining LDHs at different temperatures. The catalytic behaviours of the aforementioned LDHs and their derivatives for the catalytic wet hydrogen peroxide oxidation（CWPO） of phenol aqueous solutions were tested. Under the same experimental conditions, it was observed that iron catalysts showed bad activities （< 10% of phenol conversion）, and the copper catalysts, especially Cu-Ni-Al mixed oxide, showed higher activities. It was said that a few of iron doping into the copper catalyst could improve the dispersal of the active element （Cu）. So the quaternary mixed oxide was prepared, containing copper, nickel, iron and aluminum. According to the conversion of phenol, the ratios of four elements in the catalyst were ascertained:ΣM²⁺/ΣM³⁺=3, Fe³⁺/ΣM³⁺ =0.25, Cu²⁺/ΣM²⁺=0.25.We performed thermogravimetric analysis, X-ray diffraction and FT-IR. spectroscopy to characterize the Cu-Ni-Fe-Al LDHs and the chemical changes which take place during the calcining process. By a series of experiments, the optimum parameters in the CWPO process, using Cu-Ni-Fe-Al mixed oxide as catalyst, were ascertained. When initial phenol concentration was 400mg·L^-1, optimum conditions required for 97.5% phenol conversion were as follows: catalyst concentration was 400 mg·L^-1, M_H2O2/M_phenol （molar ratio） was equal to 12, reaction time was 60 min, reaction temperature was 60℃and the initial pH value was not adjusted （=6.5）. The catalyst also showed good activities after reusing 4 times, and the conversion of phenol was 93.5%.We also performed high performance liquid chromatography （HPLC） to analyze the products of phenol degradation at different reaction time in the paper. The analytical results indicated that hydroquinone, catechol, maleic acid and other compounds were existed. It was concluded that the hydroxylation of phenol to hydroquinone and catechol as a first step with a further oxidation of the dihyoxylbenzenes to benzoquinones. Then hydroxyl radicals sequentially attacked the aromatic rings of these compounds to cause ring opening. At this stage, maleic acid and fumaric acid were the major products. Maleic acid and fumaric acid could be oxidized to a number of other organic acids, including oxalic acid and formic acid, which can be oxidized to CO₂ and H₂O.更多还原