Preparation Of Cerium-based Catalysts And Their Performance In Catalytic Oxidation Of Ethyl Acetate

VOCs play an important role in air pollution and threat to ambient air quality and human health.Catalytic oxidation technology is considered to be one of the most promising VOCs treatment technologies due to its high efficiency,low energy consumption and no secondary pollution,and its core lies in the development of highly active catalysts.The rare earth metal oxide CeO2 is widely used in the field of VOCs catalysis because of its excellent oxygen storage and release capacity and high oxygen vacancy concentration.The morphological modulation of CeO2 catalysts has a significant effect on their catalytic activity.When CeO2 was used as the "active support",it can provide more active sites and surface oxygen vacancies in combination with noble metals,and exhibits excellent low-temperature catalytic activity.Therefore,in this paper,the catalytic oxidation of ethyl acetate by cerium-based catalysts was selected as the research system,CeO2 catalysts with different morphologies were controllably synthesized and noble metal-loaded cerium-based catalysts were constructed to investigate the structure-effect relationship between CeO2 morphology and catalytic activity,metal-support interactions and the effect of bimetallic loading on the catalytic activity of ethyl acetate.(1)Targeted preparation of CeO2 catalysts with different morphologies and their structure-effect relationships for the catalytic oxidation of ethyl acetate.The construction of CeO2 morphology was controlled by adjusting the conditions of precipitant,alkali solution concentration,hydrothermal reaction temperature and time in the hydrothermal method,and CeO2 catalysts in the shape of nanocubes(NC),spindle(SP)and nanomicrospheres(NS)were prepared in a targeted manner,the performance of CeO2 catalysts with different morphological structures for the catalytic oxidation of ethyl acetate was tested,and the structure-effect relationships between CeO2 catalysts and the catalytic activity of ethyl acetate were analyzed.The results showed that the activity order of CeO2 with different morphologies for catalytic oxidation of ethyl acetate was as follows:CeO2-NS>CeO2-SP>CeO2-NC,corresponding to T90 of 187,196 and 229℃,respectively,and the microspherical CeO2-NS had better morphological effect in catalytic oxidation of ethyl acetate.(2)Preparation of Pd/CeO2 catalysts and their metal-support interactions for the catalytic oxidation of ethyl acetate.The Pd/CeO2 catalyst with CeO2 as the active support was constructed by introducing the noble metal Pd.The performance of catalytic oxidation of ethyl acetate was tested,and the interaction between the noble metal Pd and CeO2 supports with different morphologies was analyzed.The results indicated that the introduction of Pd improved the surface microenvironment of the Pd/CeO2 catalyst,and the metal-support interactions promoted the low-temperature catalytic oxidation activity of ethyl acetate.The order of activity of Pd/CeO2 catalyst as followed:Pd/CeO2-SP>Pd/CeO2-NS>Pd/CeO2NC,corresponding to the T90 of 180,186 and 209℃,respectively.Pd exhibited stronger metal-support interaction with spindle-like CeO2-SP and better low-temperature catalytic activity.(3)Preparation of bimetallic Pd-Au/CeO2-SP catalysts and their effects on the catalytic oxidation of ethyl acetate.Attempt to introduce Au and construct spindle-like bimetallic PdAu/CeO2-SP catalysts with different Pd:Au ratios together with Pd,the catalytic oxidation performance of ethyl acetate was tested and the bimetallic-carrier interactions were analyzed.The results showed that the Pd-Au/CeO2-SP catalysts constructed by bimetallic Pd and Au with CeO2-SP had better catalytic activity on ethyl acetate than CeO2-SP,but did not compare favorably with the monometallic Pd/CeO2-SP catalysts,only the the sample with a Pd:Au molar ratio of 3:7 exhibited a slightly improvement in low-temperature catalytic activity.