Study On Preparation Technology Of CeO₂-WO₃/TiO₂ Catalyst And Its Effect On Denitration Performance

NOx is one of the main sources of air pollution.Since the 12th Five-Year Plan,China has been increasingly strict in controlling NOx emissions.At the present stage,the most widely used NH3-SCR denitration technology,in which the catalyst is the core of the technology,however,the vanadium-based denitration catalyst being used on a large scale has the problem of narrow denitration temperature zone and hazardous waste after use.Cerium oxide is very suitable as the active component of denitration catalyst because of its strong oxygen storage and redox performance,and it contains more acid sites and is easy to adsorb NH3.In this paper,using cerium nitrate,ammonium metatungstate and anatase type titanium dioxide as raw materials,CeO2-WO3/TiO2 catalyst was prepared by co-precipitation method.The effects of Ce,W ratio,roasting temperature and time on the catalytic denitration performance were studied by orthogonal experiment.The results showed that the influence of each factor on the denitration performance of the catalyst was as follows:calcination temperature>tungsten material>cerium material>calcination time.The optimum,experimental conditions for denitration of the catalyst were as follows:40%cerium and 8%tungsten,500℃ and 0.5h respectively.Under these conditions,the width of the catalyst active temperature zone reached 310℃(215-525℃).The influence of each factor on the crystallinity of the catalyst is as follows:tungsten material amount>roasting temperature>roasting time>cerium material amount.The lowest crystallinity of the catalyst was obtained under the following experimental conditions:40%cerium,8%tungsten,200℃,1.5h.The crystallinity of the catalyst under these conditions is 91.17%.XRD,XPS,BET,H2-TPR and NH3-TPD were used to study the effects of Ce,W content,phase composition,surface element content,acid site activity and reductivity on the sell-out performance of the catalyst.The results showed that the XRD patterns of the catalysts with different Ce and W contents showed no significant difference,indicating that the change of Ce and W supplemental levels had no significant effect on the phase composition of the catalysts.When WO3 content increased,BET specific surface area,pore volume and average pore size of the catalyst all increased.When WO3 content increased to 8%,the content of Ce and W on the catalyst surface increased significantly,and the proportion of Ce3+ and chemisorbed oxygen Oα increased,and the activity of the catalyst was improved.When the content of CeO2 increases,the content of Ce element on the surface of the catalyst first increases,then decreases,and reaches the highest when the content of CeO2 is 40%.As the ratio of Ce3+increases,the ratio of chemisorbed oxygen Oα increases slightly,which makes the oxygen vacancy on the surface of catalyst increase and the rate of NH3-SCR reaction increase.The increase of CeO2 content also makes the catalyst have better reduction performance at low temperature,which shows that the denitration ability is improved at low temperature.The 8WO3-40CeO2/TiO2 catalyst has better NH3 adsorption capacity in the high temperature region,which is reflected in the improvement of denitration capacity at high temperature.