Study On Catalytic Performance Of Magnetic Transition Metal Supported Catalyst Based On γ-Fe₂O₃ Support In NO+CO Reaction

Transition metal oxides have been widely studied because of their price,excellent catalytic activity,and low environmental pollution,so they have been widely studied as popular materials that can replace precious metals in the field of catalysis;while magnetic materials are regarded as good catalyst carriers after loading other transition metal oxides with excellent activity on it,they can not only guarantee the catalytic activity,but also improve the catalytic performance Through the magnetic properties of the catalyst used for convenient and quick recovery.In this paper,the most common magnetic material（M_xO_y/γ-Fe₂O₃）is selected as the carrier,and other transition metal oxides are introduced on this basis.The scanning electron microscope（SEM）,high power transmission electron microscope（HRTEM）,X-ray diffraction（XRD）,H₂ Temperature programmed reduction（H₂-TPR）,X-ray photoelectron spectroscopy（XPS）,in situ diffuse reflectance infrared fourier transform spectra（in situ DRIFTS）and other methods have been used to characterize the composite transition metal oxide/γ-Fe₂O₃catalyst,in order to explore the relationship between different catalytic performance and their morphology,electron transfer and redox ability,and based on the above characterization results,attempts to explore the mechanism of the catalyst catalyzing the NO+CO reaction.The ferromagneticγ-Fe₂O₃ solid powder was prepared by hydrothermal method at low temperature,and a series of transition metal oxide catalysts supported byγ-Fe₂O₃ were synthesized by co-precipitation method,including Ce O₂,Co₃O₄,Cu O and Ni O.Through the above characterization,it can be seen that when Ce O₂ andγ-Fe₂O₃ are loaded,they have higher auto and catalytic performance.This is mainly because the interaction between the two occurs after the loading,which makes the electron transfer the most,which affects the overall catalyst activity;and the composite catalyst sample of Cu O andγ-Fe₂O₃ has better catalytic performance below 150°C.This is mainly because the composite of Cu O andγ-Fe₂O₃significantly improves the overall oxidizability,enabling it to be participated in the catalytic reaction process at a lower temperature.In addition,all the above samples as catalysts participate in the NO+CO reaction,the overall performance of the L-H mechanism.A series of different ratios of Co₃O₄/γ-Fe₂O₃ were prepared using the same method.It was found that the composite catalyst supported by the active component of Co₃O₄ and theγ-Fe₂O₃ carrier had better activity than before.When the ratio of the two metal oxides is at 4:9,the catalytic activity is the most excellent.The reasons are:1)The two metal oxides have a part that grows along the（330）crystal plane together,forming more defects;2)The electron transfer of the two metal oxides makes the surface have many oxygen vacancies and improves the oxidation-reduction capacity of the catalyst;in addition,after magnetizing the catalyst,the activity in the low temperature section becomes better than before,because the magnetic field of the catalyst can be adsorbed the additional paramagnetic gas which in the reaction atmosphere to improve the performance of the catalyst.The composite catalyst supported by the active components of Ni O and Co₃O₄ and theγ-Fe₂O₃ carrier has good activity.When the mass ratio of the three metal oxides is 4:33:49,the catalytic effect on the NO+CO reaction is the best.After magnetization,the catalytic performance of the catalyst is further enhanced.This is mainly because:1)The electron transfer interaction of the two metal oxides makes the surface have many oxygen vacancies and improves the oxygen storage capacity of the catalyst;2)After magnetization,the magnetic field of the catalyst in the low temperature section can adsorb additional paramagnetic gas NO in the reaction atmosphere.