制备方法对CeO2及CoOx/CeO2催化燃烧甲苯的影响

Effect of Preparation Methods of CeO2 and CoOx/CeO2 on Catalytic Combustion Toluene

挥发性有机物(VOCs)是形成雾霾和臭氧的主要前驱物,而且多数具有毒性,对人体有较大的危害,因此控制其污染排放十分必要。催化燃烧是一种有效处理VOCs的方法。本文研究了制备方法对CeO2及CeOx/CeO2催化燃烧甲苯的影响,并对性能差异的原因进行分析。采用热分解法、化学沉淀法和水热法分别制备CeO2,并通过浸渍—焙烧将15%的CoOx负载在不同方法制备的CeO2上,以甲苯为目标污染物,对CeO2及CoOx/CeO2催化性能进行评价,并通过XRD、BET、SEM、H2-TPR和Raman对催化剂进行物理化学性能表征。结果表明:在甲苯浓度为1000μL/L,空速为20000 h-1测试条件下,化学沉淀法制备的CeO2-P具有最好的催化活性,在375℃达到80%的甲苯去除率;将其与Co物种复合后,Co/CeO2-P能在255℃达到90%的去除率。300℃下,经过78 h的长周期实验,Co/CeO2-P依然保持100%甲苯去除率。化学沉淀法制备的CeO2-P,具有更小的晶粒尺寸、较大的比表面积和更好表面氧化还原性能,因此其具有更好的催化活性。CeO2与Co物种复合后,得益于CeO2的大比表面积和优异氧化还原性能,形成更多Co3+,并且氧化铈能提供丰富的表面活性氧物种,使得CoOx/CeO2-P具有最佳的催化活性和稳定性。不同方法制备的CeO2拥有不同的比表面积和表面氧化还原性能,这是影响其催化活性的主要因素。

Volatile organic compounds(VOCs)are the main precursors for the formation of haze and ozone,and most of them are toxic and cause great harm to the human body,so it is necessary to control their pollution emissions.Catalytic combustion is an effective way to deal with VOCs.The effects of preparation methods on the catalytic combustion of toluene by CeO2 and CeOx/CeO2 were studied,and the reasons for the differences in performance were analyzed.CeO2 was prepared by thermal decomposition method,chemical precipitation method and hydrothermal method,then 15%CoOx was supported on CeO2 by dipping-roasting.Toluene was used as the target pollutant to catalyze CeO2 and CoOx/CeO2.The performance of catalytic oxidation was evaluated,and the physical and chemical properties of the catalyst were characterized by XRD,BET,SEM,H2-TPR and Raman.The results showed that:under the test conditions of toluene concentration of 1000μL/L and space velocity of 20000 h-1,CeO2-P prepared by chemical precipitation method had the best catalytic activity,reaching a toluene removal rate of 80%at 375℃.After the Co species were recombined,Co/CeO2-P could reach 90%removal rate at 255℃.At 300℃,Co/CeO2-P still maintained 100%toluene removal rate after a long period of experiment for 78 h.CeO2-P prepared by the chemical precipitation method had a smaller grain size,a larger specific surface area,and better surface redox properties,so it Showed better catalytic activity.After the combination of CeO2 and Co species,due to the large specific surface area and excellent redox performance of CeO2,more Co3+was formed,and cerium oxide could provide rich surface active oxygen species,making CoOx/CeO2-P the best catalytic activity and stability.CeO2 prepared by different methods had different specific surface areas and surface redox properties,which were the main factors affecting its catalytic activity.