Research On Mercury Oxidation And Denitrification Properties Of The Vanadium Series Catalyst Containing Cerium

In our country,the mercury content in coal is about 2 times of the world average.Coal burningemissions large amounts of mercury and also does great harm to the environment and human health. In coal-fired flue gas mercury mostly exist in elemental form, and because of its characteristics of volatile and difficult to soluble in water,it’s difficult to removal. Therefore, the use of the existing SCR denitration device to elemental mercury oxide as stable compounds, and through the subsequent flue gas dust removal and desulfurization device removal, is one of the important research direction of mercury from flue gas to take off. Based on commercial V2O5—WO3 / Ti O2 denitration catalyst as the foundation, adopts the method of cerium doped to adjust the formula, the catalyst’s denitration, mercury performance, to explore the mechanism of oxidation of elemental mercury.Firstly, impregnation method is used to load the Ce O2 on vanadium series SCR catalysts.The prepared catalysts have been characterized and the results show that the catalyst’s surface morphology, specific surface area and pore structure decrease slightly. The average pore size is between 13~15nm. Effect of Ce-doped on the catalyst’s microscopic properties is smaller. The support Ti O2 all exist in the form of anatase phase in catalyst. The active component V2O5 highly disperses on the surface of the support when its content is below 1%. When Ce O2 content increases to 5%, it begins to form micro-crystalline area of cerianite phase.Secondly, this thesis examines the denitration catalyst performance. With Ce after denitration rate has a tendency to move to higher temperature. In the temperature range of 150~300℃, the activity denitration doping are falling, have some before but in the 300~450℃ temperature range before the denitration activity relatively cerium doped are slightly increased, and at 450℃ still has high denitration rate. In the active component in this temperature range V2O5 and Ce O2 significant reduction of NO action occurred.Thirdly, investigates the mercury oxidation of the flue gas composition on the catalyst performance impact. SO2 oxidation of mercury has a certain role in promoting, mainly under the condition of oxygen, generate Hg SO4 promoted the oxidation of mercury. NH3 on mercury oxide has a certain inhibitory effect, because of NH3 on the catalyst surface and HCl competitive adsorption, occupy the active site of catalyst. In the process of oxidation of mercury removal, HCl gas is the main activity. When the presence of O2 and HCl in flue gas, mercury catalyst oxidation has obvious efficiency increases, when 20 ppm HCL, 4% O2, 400℃ can reach 98%, 1 language-learning. 5 v5w/Ti mercury oxide catalyst has the best effect. In reducing the vanadium content at the same time increase the amount of doped cerium help improve the quality of mercury oxidation activity, is due to the active component of Ce O2 and V2O5 in the catalyst surface is highly fragmented, cerium and vanadium in the process of mercury oxidation reaction happened because of synergy.Finally, the mercury oxidation mechanism of the catalysts were explored. With Ce did not affect the surface of the catalyst after the group. Catalyst surface hydroxyl bond, stable in number of wavelengths, 3630cm-1. The introduction of Ce is mainly affected the amount of catalyst B a sour, L acid concentration has no obvious impact. Doped Ce later as the V content is lower, as a direct result of the V5+-O combination of keys. V content from 1% to 0.1%, B acid concentration therefore dropped to 0.009 tendency tendency from 0.157 g/g. L acid concentration fluctuation near the tendency for 0.2 g. For elemental mercury in Ce elements on the surface of the catalyst removal process can be broken down and simplified as the following three steps: the element mercury and HCl gas adsorption on the surface of the catalyst, active site; Ce O2 catalyst surface lattice oxygen, oxidation state element mercury adsorption or intermediate species, generate Hg O or Hg-Cl in the middle of the species, to react with Cl or HCl, etc to form stable Hg Cl2; The gas phase O2oxidationlow-cost Ce2O3, Ce O2 formation, and the lattice oxygen of the catalysts were added. At this point, the whole process completed the Ce4+â†' Ce3+ cycle and mercury oxidation Hg0â†'Hg2+.