Noble Metal Catalysts Design,Preparation And Its Performance For Catalytic Oxidation Of Benzene

Volatile organic compounds?VOCs?are a serious threat to human health and environmental safety;therefore great efforts are devoted to searching effective technologies for the removal of VOCs.Therein,the catalytic oxidation attracts widespread attention for the removal of VOCs for its low consumption,speediness,operation safety and environment friendly characteristics.At present,noble metal and metal oxide catalysts are two major typical catalysts for the degradation of VOCs.In recent decades,with the continuous improvement of preparation strategies,characterization technologies and test means,the research on the synthesis and application of nanostructured materials has been developed significantly,which brings great opportunities and challenges for their application for the efficient purification of VOCs.Herein,in view of the noble metal catalysts,aiming to enhance the catalytic performance of per unit noble metal for the reduction of the metal loading amount,the relationship between structure,morphology and catalytic performance of the catalyst is explored by means of structural control and interface modification.The main research contents and results are as follows:?1?Porous polyhedron Pd/Co₃O₄ catalysts are synthesized by pyrolysis of Co-based ZIF-67.By adjusting calcination temperature,the proper porosity,nanoparticle size and chemical valence state of metal of the catalyst could be controlled,which could affect the distribution of reactants,the properties of surface active oxygen,thus affecting the activity of the catalyst.High specific surface area and rich pore structure is favorable for the exposure of active sites on the surface of catalyst,which is advantageous to the adsorption and reaction of reactants and surface oxygen.And the electron transfer from Pd to O for Pd/Co₃O₄-PP-350,may make the Oads more active.The results of H2-TPR also point out that PdOx on Pd/Co₃O₄-PP-350 has the best reducibility,i.e.the oxygen activity is the highest.Therefore the Pd/Co₃O₄-PP-350 exhibits the highest catalytic performance for the complete oxidation of benzene.?2?The decoration of reduced graphene oxide?rGO?in the Pt/Al₂O₃ catalyst can effectively increase the specific surface area of the catalyst.Moreover,it is of interest to note that the order of catalytic activity is the same as the order of binding energy for Oads,suggesting that the Oads plays a crucial role in the complete oxidation of benzene.Then,the transfer of electrons from rGO to Pt and O in the Pt-rGO/Al₂O₃ catalyst reduces the binding energy for Oads in order to make the surface adsorbed oxygen more active,so as to improve the catalytic efficiency of the catalyst.?3?The morphology of the active components could be finely controlled by the method of solution-based synthesis.By adjusting the reaction temperature and the addition amount of Ag?or Au?,the morphology of Pt could be effectively regulated,and finally the dendritic and spherical Pt nanoparticles can be obtained respectively.Then these nanoparticles are loaded on ?-Al₂O₃ substrates for the catalytic oxidation of benzene and various characterization tests.The results demonstrated that the dendritic Pt/Al₂O₃ catalysts which possess more and higher active adsorption oxygen on the surface have a superior catalytic activity to the spherical Pt/Al₂O₃ catalysts for the complete oxidation of benzene.?4?The bimetallic Pt-Cu particles with different Cu contents are synthesized by a wet-chemistry method in oil amine,and their activities for catalyzing benzene oxidation are evaluated on the ?-Al₂O₃ supports.Because the Cu content,loading,dispersion and morphology of the catalysts are different,it is difficult to find a direct correlation between the properties and the activity of the catalyst.However,it can be found that the TOF of the catalyst is positively correlated with the model calculated size of the Pt particles calculated by CO-pulse chemisorption.Then,there is a positive correlation between the activity of the catalyst and the number of Pt atoms on the surface as well as the calculated size of the Pt particles.Therefore,it is necessary to balance the number of Pt atoms on the catalyst surface and the size of the Pt particles in order to maximize the activity of the catalyst.In addition,the Pt-Cu/Al₂O₃ particles with Pt/Cu molar ratio of 1/1 have the best activity in the catalysts tested.