Electrodeposition Preparation And Application Of Co/Mn-based Monolithic Catalysts

Monolithic catalyst is widely applied in various fields,and exploration on preparation methods for monolithic catalyst is critical for their industrial applications.The electrodeposition is a facile strategy to deposit active components on monolithic substrates,due to the operation simplicity and in-situ growth of active components on supports.Aiming at the defects of the current integrated catalyst preparation method:complex preparation,uneven loading,weak adherence,the electrodeposition preparation method,a new way to prepare the monolith catalyst,was explored in this work.According to the electrochemical properties and catalytic properties of the materials,cobalt and manganese oxides were selected as the active components of monolithic catalysts.A series of Co/Mn-based catalysts were prepared by electrodeposition method and evaluated in C3H8 or NO oxidation reactions.Further,the effect of deposition conditions on morphology,crystalline phase and catalytic properties of the obtained samples were systematically studied.It can be concluded that:(1)A series of Co3O4 monolithic catalysts were prepared by electrodeposition method.The effects of different deposition time on their physicochemical properties and catalytic oxidation performance of propane were investigated.It is found that the catalytic performance of Co3O4 prepared by electrodeposition method is better than that of powdered Co3O4 prepared by thermal decomposition method.Further studies show that the catalyst with shorter deposition time has higher Co2+content and weaker Co-O bond,and thus showed superior catalytic performance for C3H8 oxidation reaction.The catalytic rate of Co-NF-300s with the shortest deposition time is 6.7×10-4 mol/gCo3O4/s at 220?,and the activation energy is as low as 46 kJ/mol.Co-NF-300s also also possesses excellent stability of over 80%propane conversion for 40 h without notable decrease at 300?.(2)The MnOx monolithic catalysts with different valence states were prepared by electrodeposition method.The effect of deposition voltage on phase,morphology and the performance of catalytic oxidation of low concentration NO were investigated.It is found that Mn ions get electrons under negative voltage and MnOx become lower-valence manganese-based oxides,while under positive voltage,Mn ions lose electrons and MnOx turns into high-valence manganese-based oxides.Mn2+is electronized at a negative voltage,but it is calcined to form Mn304.Compared with the deposited products Mn3O4 and MnO2 under negative voltage,the MnO2 obtained under positive voltage had smaller particle size of about 20nm,showing better catalytic oxidation of NO performance at NO concentration=l Oppm and space velocity of 50000ml/(gh).The catalytic conversion rate of NO at 50? is 70%.(3)A series of cobalt-manganese monolithic catalysts were prepared by electrodeposition method.The effect on phase structure,particle size and catalytic oxidation of NO of different Mn/Co ratios(5:1,2:1,1:1,1:2)were investigated.It is found that with the increase of Mn content,the phase structure changes from Co3O4 to Mn3O4.When Mn:Co=2,cobalt-manganese composite oxide(CoMn)(CoMn)2O4 formed.The particle size decreases with the increase of Mn content:the sample with Mn:Co=5 has the the smallest particle size of 3-4 nm.Mn:Co=2 exhibited the best NO oxidation performance,and NO with concentration=10 ppm was completely converted at 50? and its good properties were related to the(CoMn)(CoMn)2O4 structure and the smaller particle size.