赵梦戈,李济吾.三维有序介孔铈钴铜催化剂的制备及其降解邻二甲苯的机制[J].环境科学学报,2019,39(6):1959-1969
三维有序介孔铈钴铜催化剂的制备及其降解邻二甲苯的机制
- Preparation of three-dimensional ordered mesoporous ceric cobalt copper catalyst and its degradation mechanism for o-xylene
- 基金项目：浙江省自然科学基金项目（No.LY16E080001）
- 赵梦戈
- 浙江工商大学环境科学与工程学院, 杭州 310012
- 李济吾
- 浙江工商大学环境科学与工程学院, 杭州 310012
- 摘要：以PMMA为模板，通过聚乙二醇（PEG400）和柠檬酸辅助的溶胶凝胶法制备三维有序介孔铈钴铜（3DOM 3C）催化剂，应用BET、SEM、XRD和XPS等对不同煅烧温度的3DOM 3C催化剂进行表征分析，研究了催化剂活性及其影响因素，并利用FT-IR和GC-MS对降解产物进行分析，推测出催化降解邻二甲苯的机理.结果表明，煅烧温度500℃时制备的3DOM 3C催化剂表面具有三维介孔结构，且分散均匀，表面的晶体氧化物最少，存在大量的Cu2+、Ce3+和表面氧，催化剂表面存在更多的固溶体、表面活性位点和氧空位，有利于提高催化活性.在邻二甲苯初始浓度600 ppm、空速16000 h-1、50% O2条件下，煅烧温度500℃时制备的3DOM 3C催化效果最佳，在260℃时，3DOM 3C催化剂对邻二甲苯的转化率达98%，T90为250℃.3DOM 3C对邻二甲苯的转化率随着初始浓度、空速和相对湿度的升高而呈下降趋势，随着O2含量的增加而增加.气流中混入150 ppm的乙酸乙酯能够提高邻二甲苯的转化率，提高其低温催化性能.邻二甲苯催化反应后催化剂表面的O-H、C=O、C-H和金属-氧键都相应的减少，降解中间产物主要有邻甲基苯甲醛和邻甲基苯甲酸.邻二甲苯降解反应涉及Mars Van Krevelen机理（MVK），先被氧化成邻甲基苯甲醛，再进一步氧化成邻甲基苯甲酸，最终生成CO2和H2O.
- Abstract：Three-dimensional ordered mesoporous cerium cobalt copper catalyst was prepared by using PMMA as template and polyethylene glycol (PEG400) and citric acid-assisted sol-gel method. 3DOM 3C catalysts at the different calcination temperature were characterized by using BET, SEM, XRD and XPS. The catalyst activity of 3DOM 3C and influencing factors on o-xylene conversions were investigated by GC on-line detection. The degradation products were analyzed by FT-IR and GC-MS to deduct the degradation mechanism of o-xylene. The results showed that the surface of 3DOM 3C catalyst at 500℃ has a three-dimensional mesoporous, uniform structure dispersion, minimal crystal oxide on the surface, and a large amount of Cu2+, Ce3+ and surface oxygen. There are more solid solutions, surface active sites and oxygen vacancies on the catalyst surface, which improves the catalytic activity. Under the initial concentration of 600 ppm, the space velocity of 16000 h-1 and 50% O2, the 3DOM 3C prepared at the calcination temperature of 500℃ has the best catalytic effect, and its conversion of o-xylene reached 98% at 260℃, T90 was 250℃. The conversion of o-xylene decreased with the increasing of the initial concentration and space velocity, but increased with the increasing O2 content. The addition of 150 ppm of ethyl acetate to the gas stream can increase the conversion of o-xylene and low temperature catalytic performance. It showed that the O-H, C=O, C-H and metal-oxygen bond were correspondingly reduced on the surface of the catalyst after the reaction and the degradation intermediates of o-xylene were o-methylbenzaldehyde and o-methylbenzoic acid. The catalytic degradation of o-xylene involves Mars Van Krevelen mechanism(MVK), which is oxidized to o-methylbenzaldehyde and further oxidized to o-methylbenzoic acid to produce CO2 and H2O.
