Mechanism Of The Influence Of The Dispersion Of Copper-Cerium Oxide On The Surface Of Titanium-Zirconium Framework On The Denitrification Performance Of Low Temperature NH₃-SCR

Selective catalytic reduction(SCR)technology has been widely used to remove NOx from flue gas of coal-fired power plants.However,the development of low-temperature NH3-SCR denitrification catalyst remains a challenge.According to the current research progress at home and abroad,the low activity of denitrification catalyst at low temperature is the main problem affecting the application of catalyst in coal-fired power plants.The surface dispersion of the active material is a major factor affecting the activity of the catalyst.At present,there are few studies on the dispersion of active substances on catalyst surface,and few reports on the quantitative characterization and analysis of the dispersion of active substances.This paper mainly focuses on the above problems,using TiO2-ZrO2 as the carrier and copper-cerium oxide as the active component.Ultrasonic-assisted preparation of CuCe/TiO2-ZrO2 catalyst for low-temperature SCR denitrification.Qualitative analysis of dispersion was carried out by means of characterization,and the dispersion of catalyst surface active substances was quantitatively analyzed by means of multi-fractal theory.In this paper,TiO2-ZrO2 carrier was prepared by sol-gel method.CuCe/TiO2-ZrO2 catalysts were prepared by gradually impregnating active components copper and cerium on the catalyst support.When the copper-cerium oxide is loaded on the binary support at the same time,the catalyst has the best denitrification performance and the dispersibility of the active material is better.The denitrification efficiency of CuCe/TiO2-ZrO2(without ultrasound)was 89.7%at 350?.Ultrasonic-assisted preparation of CuCe/TiO2-ZrO2 catalyst,the denitrification performance of the catalyst under different ultrasonic conditions was compared by changing the ultrasonic operating temperature,ultrasonic control time and ultrasonic operation with the order of magnetic stirring.The results show that ultrasonic dispersion can significantly improve the denitrification performance of the catalyst.At the same time,the denitrification performance of catalysts with different cerium contents was analyzed.In order to qualitatively analyze the dispersibility of the catalyst surface active material,the surface morphology and surface roughness of the catalyst were analyzed by SEM and AFM electron microscopy.The results show that the average roughness of catalyst elevation distribution can be significantly reduced by ultrasonic treatment.The average roughness of the CuCe/TiO2-ZrO2(with ultrasonic)catalyst was 2.62 nm.The singularity of catalyst surface was quantitatively analyzed by multifractal theory combined with the results of electron microscopy characterization.The results show that the singularity Aa of the sonicated catalyst is 0.543,which is less than 0.578 of the catalyst untreated by ultrasound.It shows that the surface roughness condition is better and the dispersion effect is better.The BET and XPS characterization showed that the specific surface area and pore volume of the catalyst prepared by ultrasound-assisted method were increased.The content of Ce3+ on the surface of the catalyst increased,and the redox reaction on the surface of the catalyst increased,which improved the denitrification performance of the catalyst.The group changes of NH3 and NO+O2 on the surface of the catalyst were discussed and analyzed.The reaction process of reaction gas on the catalyst surface was preliminarily studied,in which NH3 was adsorbed mainly by coordination NH3 on the catalyst surface.Nitrate is the main adsorbent of NO on the surface of catalyst.Reactions on catalysts mainly occur between coordination NH3 and NO.The fractal dimension Do and the singularity Aa were used as evaluation indexes of the catalyst dispersion,and the two standards were compared with the denitrification performance of the catalyst.The results show that the surface morphology of catalysts with different chemical components has little effect on the performance of catalysts.For catalysts with the same chemical composition,the greater the fractal dimension of the catalyst,the stronger the denitrification effect;the smaller the singularity of multifractal spectrum,the stronger the denitrification effect.At the same time,the definition of catalyst dispersion,microcrystalline fineness and evaluation criteria was proposed.The effect of dispersion on the activity of the catalyst under ultrasonic strengthening conditions was obtained.