Study On Photo Thermal Catalytic Degradation Of Characteristic VOCs

With the continuous improvement of environmental awareness and the continuous strengthening of ecological civilization construction,how to efficiently manage VOCs has become a new research hotspot.According to the objectives and requirements of ecological environmental protection planning,combined with the advantages of high degradation efficiency of thermal catalysis and low energy consumption of photocatalysis,the research direction is determined to be the study of photothermal catalytic degradation of characteristic VOCs.The light field and flow field of the reaction cavity were simulated by CFD simulation,and the parameters of the reactor were determined.An experimental system was established to investigate the effects of different experimental conditions on the photothermal catalytic toluene.Through the specific heat catalytic experiment,it was proved that infrared photothermal catalysis had the characteristics of lower catalytic reaction temperature and lower energy consumption,which reduced the economic cost for the later industrial application.The physical and chemical properties of the catalysts were studied by XRD,BET,SEM,XPS,DRS and H2-TPR,and the experimental results were verified.It was inferred that the essence of infrared photothermal catalysis was MVK mechanism.The infrared photothermal catalytic reaction cavity and the full spectrum catalytic reaction cavity were simulated and optimized by CFD technology.The light field simulation of the infrared photothermal catalytic reaction cavity was carried out to verify the rationality of the cavity design.The simulation results show that there is infrared radiation in the cavity,and the infrared radiation intensity in the center of the cavity is relatively high,stable and uniform,which provides a theoretical basis for the installation of quartz tube and the placement of catalyst.The fluid simulation of full spectrum catalytic reaction chamber is carried out.Compared with the traditional reaction chamber,the improved reaction chamber adopts lower end intake,which can simplify the movement trajectory of exhaust gas in the chamber.Owing to the air inlet is prone to produce gas vortex,the volume utilization of the cavity is reduced.Therefore,the variable diameter taper method is used to reduce the generation of vortex.At the inlet speed of 0.029 m/s,the vortex phenomenon can be avoided by using 20°taper,which increases the utilization rate of cavity volume,provides a theoretical basis for industrial application and reduces the initial investment cost.The results show that the catalytic degradation efficiency of 1:3 Co₃O₄/LaMnO₃composite can be maintained above98%when the initial concentration of toluene is 100ppm,the residence time is 0.4s and the relative humidity is less than 20%.Through 30 cycles of 1:3 Co₃O₄/LaMnO₃composite,it is found that the catalytic degradation efficiency of p-toluene fluctuates in a certain range,and there is no downward trend,so 1:3 Co₃O₄/LaMnO₃has good stability.XRD characterization showed that there was strong interaction between Co₃O₄and LaMnO₃in different Co₃O₄/LaMnO₃composites;the specific surface area of 1:3Co₃O₄/LaMnO₃composite was 16.166 m²/g,and the average pore size was 27.243 mm,which proved that 1:3 Co₃O₄/LaMnO₃composite was mesoporous structure;SEM and EDS were used to study the morphology of the catalyst,and the surface morphology of the catalyst was analyzed The surface of the agent is evenly distributed.The UV Vis NIR diffuse reflectance spectroscopy（DRS）was used to measure and compare the optical response of different catalyst samples.The characterization results show that the 1:3 Co₃O₄/LaMnO₃sample has good optical response in the range of 200-2000 nm.X-ray photoelectron spectroscopy（XPS）was used to study the surface element composition,chemical state and properties of adsorbed oxygen species.Among them,O_latt/O_ads=1.41 in Co₃O₄/LaMnO₃,O_latt/O_ads=1.09 in LaMnO₃,and Co₃O₄/LaMnO₃has a higher lattice oxygen concentration.During the temperature-programmed reduction of the catalyst,it was found that due to the appropriate introduction of Co₃O₄,the area of the reduction peak increased and the hydrogen consumption increased from 2.98 cm³/g to 4.21 cm³/g in the low-temperature reduction interval.In the high temperature reduction zone,the reduction peak area increases and the hydrogen consumption increases from 12.12 cm³/g of LaMnO₃to 15.61 cm³/g.In addition,the introduction of Co reduces the temperature of the LaMnO₃high-temperature reduction peak and improves the catalytic activity of the catalyst.Through experiments and characterization results,it is inferred that the mechanism of infrared photothermal catalytic degradation of toluene is essentially the MVK mechanism of metal oxides.1:3 Co₃O₄/LaMnO₃,has a higher concentration of lattice oxygen and higher lattice oxygen activity,which are the main factors for the reaction.