尖晶石型AFe2O4催化剂的制备及其催化燃烧甲苯的研究

通过溶胶-凝胶-自蔓延燃烧法制备尖晶石型AFe₂O₄(A=Cu, Co, Ni, Mg, Zn)催化剂, 以甲苯为VOCs模拟气, 考察AFe₂O₄催化剂对VOCs的催化燃烧活性, 并采用XRD、N₂吸附-脱附、SEM、TEM、H₂-TPR、XPS对催化剂进行表征分析。结果表明: AFe₂O₄表现出较好的催化燃烧活性, 其中CuFe₂O₄的催化燃烧活性最佳, 起燃温度(T50)和完全燃烧温度(T90)分别为188℃、239℃。AFe₂O₄具有明显的片状尖晶石晶体, 并形成以介孔为主的多级孔结构, 该特点为催化剂提供了大量表面活性位。A位元素种类对其催化燃烧活性影响较大, 当A位元素为Cu时, Cu的H₂还原峰面积远大于其他元素, H₂还原温度仅为289℃, 表面亲电子氧和氧空位浓度占氧元素总量(O_ele/O_1S)的36%。CuFe₂O₄为片状反尖晶石晶型, 晶格体积仅为0.294 nm³, 并伴有CuO和α-Fe₂O₃物种。以介孔为主的多级孔结构、特有的片状反尖晶石晶型以及该晶型与CuO和α-Fe₂O₃的协同作用是CuFe₂O₄催化燃烧活性提高的主要原因。

Spinel AFe2O4 Catalysts: Preparation and Catalytic Combustion of Toluene

Nanocrystalline AFe₂O₄(A=Cu, Co, Ni, Mg, Zn) ferrite spinel catalysts were prepared by Sol-Gel auto-combustion method. In order to investigate the influence of A sites in AFe₂O₄ spinel catalysts, the catalytic combustion of toluene was investigated, and the catalysts were characterized by XRD, N₂ adsorption-desorption, SEM, TEM, H₂-TPR, and XPS. It was found that AFe₂O₄ catalysts have excellent catalytic activity. Among the catalysts, the CuFe₂O₄ catalyst obtains the highest catalytic activity, and its light-off temperature (T₅₀) and the complete combustion temperature (T₉₀) of toluene were 188℃ and 239℃, respectively. And AFe₂O₄ catalysts have obviously lamellar spinel crystal structure and the multilevel pore structures with prevalence to mesoporous, which will improve the catalytic activity of the catalysts. It is concluded that the elements of A site on AFe₂O₄ have great influence on catalytic combustion activity. The H₂ reduction temperature is only 289℃, when A site was occupied by Cu. CuFe₂O₄ has crystal lattice volume of 0.294 nm³ with CuO and α-Fe₂O₃ formed in the crystal. The concentration of electrophilic oxygen and oxygen vacancy in all oxygens (O_ele/O_1S) is 36%. Lamellar trans spinel crystal lattice, the synergies of trans spinel CuFe₂O₄ with CuO and α-Fe₂O₃, and the multilevel pore structures with prevalence to mesoporous are the main reasons for the catalytic activity improvement of CuFe₂O₄.