Study On Catalytic Oxidation Performance And Mechanism Of VOCs By Ru Supported Molecular Sieves

At present,with the continuous development of industry,the problem of environmental pollution has become more and more serious.Among them,volatile organic compounds（VOCs）have attracted wide attention from all walks of life because of their high pollution and high toxicity.In the control technology of VOCs,Decomposition of VOCs into non-toxic small molecules such as H₂O and CO₂ by catalytic oxidation reaction can completely eliminate VOCs,and the effect is excellent and widely used.Therefore,it is increasingly important to develop catalyst systems that are highly efficient,stable,and insensitive to a wide range of VOCs.Among them,noble metal catalysts have attracted extensive attention due to their excellent and stable catalytic properties,and molecular sieves have been the hotspot of research because of their high adsorption capacity and high stability.In this paper,Ru,which is relatively inexpensive in precious metals,is selected as the active component,and it is loaded into molecular sieves to prepare a supported catalyst,in order to combine the excellent properties of both precious metals and molecular sieves.The catalytic oxidation characteristics of typical VOCs（toluene and trichloroethylene）supported by molecular sieve supported Ru-type catalysts were investigated.The effects of different calcination temperatures and silica-alumina ratios on the performance of the catalysts were also discussed.The main conclusions are as follows:（1）It is feasible to load Ru onto the surface of ZSM-5 molecular sieve by excess impregnation method.The performance of the catalyst is greatly improved,the stability is good,the water resistance is good,and good catalytic oxidation is exhibited for multiple pollutants.performance.The active component Ru exists mainly in the form of Ru O2 on the surface of the ZSM-5 molecular sieve,and its dispersion degree is high;（2）The increase of calcination temperature has a certain influence on the performance of Ru/ZSM-5 catalyst.Excessive calcination temperature will cause the catalytic oxidation activity of the catalyst to decrease.The mechanism of the influence of calcination temperature on the activity of the catalyst was investigated by multiple characterization.Experimental studies have found that 350°C is a suitable calcination temperature.（3）The effect of the silica-alumina ratio of the molecular sieve support on the performance of the Ru/ZSM-5 catalyst is complicated,but the results show that the improvement of the silica-alumina ratio is beneficial to the catalytic activity of the Ru/ZSM-5 catalyst,and the excessive silicon-aluminum ratio.This will cause a decrease in catalyst performance.The mechanism of the influence of molecular sieve silica-alumina ratio on the activity of the catalyst was investigated by multiple characterization.The experimental study shows that the catalyst has the best catalytic performance when the ratio of silicon to aluminum is 150.（4）The catalytic oxidation of toluene and trichloroethylene on Ru/ZSM-5catalyst was analyzed.Toluene has two catalytic oxidation paths on the Ru/ZSM-5catalyst,and the intermediate products are benzaldehyde,benzoic acid and the like.The intermediate product of trichloroethylene on the Ru/ZSM-5 catalyst is mainly dichloroacetyl chloride.After the catalytic oxidation process,toluene and trichloroethylene are finally oxidized into small molecules such as carbon dioxide and water,and the by-products are less,and the catalytic process is thorough.