Chromium Based Catalysts And Their Thermal Catalytic Degradation Performance For 1,2-dichloroethane

With the rapid development of industry and economy,the emission of chlorinated volatile organic compounds（CVOCs）is increasing,which causes serious harm to human health and environment.Catalytic combustion is an effective and economic method to control CVOCs.The key is to develop a catalyst with low cost,high activity and good stability.In this dissertation,chromium based catalysts were developed for low-temperature catalytic combustion of 1,2-dichloroethane（1,2-DCE）.Composition and structure of the prepared catalysts were characterized by TG,XRD,SEM,XPS,N₂-BET,H₂-TPR and NH₃-TPD.Their catalytic combustion effect on 1,2-DCE was investigated by fixed catalytic reaction bed system,and the relationship between their physico-chemical properties and catalytic activity was explored.The main research contents and conclusions are as follows:（1）A series of Cr O_X/USY catalysts were prepared by rotary evaporation impregnation method with USY zeolite supporter.The results show that USY has large specific surface area（730.7 m²/g）and is rich in surface acid sites,which promote the uniform dispersion of Cr O_X on USY surface and the adsorption of 1,2-DCE.The specific surface area of this series of catalysts is as high as 450.7～649.6 m²/g.The introduction of Cr O_X improves the catalytic activity,and appropriate Cr O_X doping can reduce the by-products generation.The 30Cr O_X/USY catalyst shows the best catalytic activity with T₉₀ of 252℃.It also shows the best selectivity among the prepared catalysts,producing less chlorinated by-products.（2）Ce-MOF was successfully prepared using pyromellitic acid as the organic ligand.A series of flower-like Cr O_X/Ce O_X composite catalysts were prepared by in-situ synthesis using Cr O_X as the modified component and Ce-MOF as supporter.This series of catalysts show high specific surface area of 143.9～229.3 m²/g.The heterovalent substitution between chromium and cerium leads to lattice defects and more oxygen vacancies on the catalyst surface,which promotes the redox process.Among them,the 30Cr O_X/Ce O_X catalyst shows the best catalytic activity for 1,2-DCE with T₉₀ of 285℃.（3）ZIF-67 with high yield was successfully prepared by liquid phase diffusion method under mild reaction conditions and short reaction time.A series of Cr O_X/Co₃O₄ catalysts were prepared by impregnation method.The 30Cr O_X/Co₃O₄ composite catalyst shows high specific surface area（104.3 m²/g）and catalytic activity with T₉₀ of 267℃.During the stability test,it can keep the conversion above 90%for 24 h at 290℃ and 100%for 24 h at 300℃.