Study On The Catalytic Combustion Of Toluene By Foam Metal-based Monolithic Catalysts

Volatile organic compounds（VOCs）are common pollutants in industrial production,and not only pollute the environment,but also cause great harm to the human body.Benzene,formaldehyde,vinyl chloride,trichloroethylene,and 1,3-butadiene in VOC have been listed as a class of carcinogens.Long-term exposure to environments containing VOCs can lead to chronic poisoning,damage to the liver and nervous system,and even cancer.Therefore,the governance of VOCs is of great significance.Currently,catalytic combustion is considered one of the most effective methods for handling VOCs because of its unique advantages.VOCs emitted in industrial production are characterized by high space-velocity.Therefore,the advantages of monolithic catalysts such as low pressure drop and high mechanical stability make them stand out among many catalysts.It is generally believed that the active components of monolithic catalysts and the anchoring force between the carrier and the active material are key factors affecting the performance of the catalyst.In this paper,first,a series of catalysts were prepared using foam copper as a carrier and the impregnation method by successively loading transition-metal oxides and coatings onto the carrier.Starting with the types and proportions of active substances,the optimal proportion of active substances of the catalyst was explored.At the same time,with foam nickel as the carrier,active substances were deposited directly in situ on the surface of the foam nickel carrier by an electrochemical deposition method,and catalysts with strong anchoring force with the carrier were prepared.The specific research content and results are as follows.（1）The copper foam based monolithic catalysts and nickel foam based monolithic catalysts were prepared by the impregnation method using nickel foam and copper foam as carriers and Co,Ni,and Ce elements as active substances using the same preparation method and conditions,and the catalysts were tested and investigated by varying the type and ratio of the loaded active substances.The results showed that the catalytic activity(T₉₀)of the catalyst prepared on a copper foam carrier was better than that of the nickel foam carrier(T₉₀).（2）The effects of different molar ratios of two metal elements（Co/Ce and Ni/Ce）loaded on the catalytic activity of the copper foam-based catalysts were further investigated,and the effects of air velocity,stability,and ratio were examined.The results showed that the Co₁Ce₂@Cu-F catalyst achieved 90%conversion of toluene at 237°C at a weight hourly space velocity of 15000 m L·g^-1·h^-1.The catalyst showed no significant decrease in catalytic activity toward toluene after three cycles and still achieved more than 90%conversion of toluene at250°C with good cycling stability.Comprehensive characterisation of the XRD,XPS,and H₂-TPR analysis results showed that the high activity of the catalyst was attributed to the interaction between Co and Ce,which not only improved the low-temperature reduction performance of the catalyst,but also provided oxygen vacancies due to the abundant Co²⁺and Ce⁴⁺content as well as adsorbed oxygen species on the surface,facilitating the catalytic reaction.（3）Electrochemical deposition method was used to deposit metal ions directly on the surface of nickel foam as the active substance using nitrate solution as the deposition solution.By examining and optimizing the deposition voltage,active substance species,deposition time,and deposition solution concentration,it was concluded that the Co/Cu composite metal oxide catalyst was more effective at-2 V and 600 s under the same preparation conditions as the experimental conditions.The catalytic performance of the catalysts was investigated for different ratios of Co/Cu composite metals as active components.The results showed that the Co₂Cu₁/NF catalyst achieved 90%conversion of toluene at 225°C at a weight hourly space velocity of 20,000 m L·g^-1·h^-1.Characterization by SEM,XPS,Raman,and H₂-TPR showed that the high activity of the Co₂Cu₁/NF catalyst was attributed to the higher specific surface area in a lamellar and linear form brought to the catalyst by electrodeposition,the strong interaction between Co and Cu and the fact that this interaction caused lattice defects to occur in Co₃O₄,providing more active oxygen vacancies and facilitating the oxidation reaction.The higher O_latt/O_ads（lattice oxygen/adsorbed oxygen）ratio of Co₂Cu₁/NF is also one of the reasons for the better catalytic activity of the catalyst.