微波辐射下La-Mn-Co金属氧化物的甲苯降解性能

Catalytic performance of La-Mn-Co oxides for toluene oxidation under microwave irradiation

以La-Mn-Co金属氧化物作为催化剂,研究了微波辅助下催化剂的甲苯降解性能,分析了形貌特征、活性基团、加热方式对催化剂性能的影响.活性测试结果表明当金属镧锰钴比为4∶1∶10时所制备的La-Mn-Co金属氧化物(La_(0.8)Mn_(0.2)Co_(2))在微波辐射下表现出最好的甲苯降解性能,其在甲苯降解率为90%(T_(90))所对应的温度为192℃(甲苯浓度为2 800 mg/m^(3),质量空速为90 000 mL/(g·h)),高于常规热场T_(90)所对应的温度239℃.La_(0.8)Mn_(0.2)Co_(2)金属氧化物较好的催化活性得益于其拥有更大的比表面积、更小的粒径、更多的活性基团以及丰富的Mn^(3+)、Mn^(4+)和Co^(3+)物种.同时,反应动力学分析结果表明,相同低温反应条件下(120℃),La_(0.8)Mn_(0.2)Co_(2)氧化物在微波场中的表观活化能(19.22 kJ/mol)明显低于常规热场(26.13 kJ/mol),其反应速率是常规热场的3.36倍.

Microwave-assisted catalytic oxidation of toluene was investigated over La-Mn-Co oxides.The effects of morphological characteristics,active groups,and heating methods on the catalytic oxidation performance of catalysts were analysed.The activity test results show that La-Mn-Co oxide with a La∶Mn∶Co ratio of 4∶1∶10 exhibit best toluene degradation performance under microwave irradiation,and its degradation rate is 90%(T_(90)) at 192 ℃(at toluene concentration is 2 800 mg/m^(3) and weight hourly space velocities is 90 000 mL/(g·h)),which is higher than the conventional thermal field T_(90) corresponding temperature at 239 ℃.The better catalytic performance of La_(0.8)Mn_(0.2)Co_(2) metal oxide attributes to larger specific surface area,smaller particle size,more reactive groups,and an abundance of Mn^(3+),Mn^(4+) and Co^(3+) species.Meanwhile,the results of the reaction kinetic analysis show that the apparent activation energy of La_(0.8)Mn_(0.2)Co_(2) oxide in the microwave field(19.21 kJ/mol) is significantly lower than that of the conventional thermal field(26.13 kJ/mol) under the same low temperature reaction conditions(120 ℃),and its reaction rate was 3.36 times higher than that of the conventional thermal field.