Composite Oxide Catalysts Used For PVOCs Catalytic Elimination

Phenyl volatile organic compounds（PVOCs）have been endangering both the environments and the human beings,such destroying ozone layer in atmosphere,producing photochemical smog,and leading to health problems of cancer,deformity,mutation,and so on.In present,among many PVOCs abatement methods the catalytic combustion is one of the most preferred approachs,with advanteges of low-energy consumption,high efficiency,and no secondary pollution,thus having attracted wide attentions arround the world.The core issue of the PVOCs catalytic combustion is the design and development of catalytic materials.In this dissertation,CeCu and NiMn oxide catalysts prepared by complexation and co-precipitation methods were characterized by XRD,H₂-TPR,O₂-TPD and XPS,in order to study the effect of preparation conditions on the physical and chemical properties of catalysts,including crystal structure,surface composition,reducibility,the desorption performance of O₂,and catalytic combustion performance of PVOCs.The main conclusions are listed as following:1.For CeCu oxide catalysts prepared by complexation method,high calcination temperature facilitates CuO species dissolve into CeO₂ lattices to form CeCu oxide solid solution.The formation of CeCu oxide solid solution can promote the interaction between different metal-oxygen species and effectively weak the bonding energy of “Ce-O” and “Cu-O” bonds.This process can activate “metal-oxygen” bonds,so that it increases the amount of active oxygen species in CeCu oxide catalysts,which improves PVOCs catalytic combustion activity of the corresponding catalysts.2.When Ce/Cu molar ratio is 3.0 and CA/M（Ce+Cu）molar ratio is 1.8,the CeCu oxide catalysts（CeCu350,calcined at 350 °C for 3.0 h）possess superior reducibility and oxygen delivery capacity.At the reaction temperature of 225 °C,CeCu350 shows good catalytic combustion activity for methylbenzene（94.3%）,with preferable thermal stability in reaction process.Meanwhile,the same catalyst also shows good catalytic combustion activity for PVOCs,the order of whicvh follows: ethylbenzene > xylene > toluene > benzene.3.For the NiMn oxide catalysts prepared by co-precipitation method,high calcination temperature can promote the interaction between NiO and MnOx to form NiMn₂O₄ spinels.The formation of NiMn₂O₄ spinels improves the reducibility and oxygen storage capacity of the corresponding catalysts with the capacity of active oxygen species delivering at low reaction temperature for catalytic combustion reaction,as a result,the NiMn oxide catalysts exhibit good catalytic combustion activity in reaction process.With the Ni/Mn molar ratio dosage of 1.0,the prepared NiMn oxide catalysts NM-CP1 display better reducibility at low temperature than other catalysts with different metal dosage,meaning the corresponding catalyst can provide aboundant active oxygen species for the toluene catalytic combustion reaction under gentle conditions,so that the toluene catalytic conversion over the catalyst reaches up to 90.2% at 230 °C.4.The addition of oxidant oxidizes low-valence Mn species（+2）to high-valence（+4）,which improves the reducibility and the active oxygen delivery capacity of NiMn oxide catalysts at low reaction temperature.Especially,when the NM-HP oxide catalyst was oxided by H₂O₂,it shows the better reducibility and stronger active oxygen delivery capacity,and it also exhibits the best catalytic combustion activity with toluene catalytic conversion of 92.3% and favourable thermal stability at 200 °C.Meanwhile,this catalyst shows good catalytic combustion activity for PVOCs,the catalytic combustion activity can be described as following sequence: toluene > xylene > ethylbenzene > benzene.