Metal Mixed Oxides Derived From Layered Double Hydroxidesfor Catalytic Oxidation Hg~0 In The Flue Gas

Mercury is a major pollutant because of its toxicity, mobility in the food chain, and bioaccumulation. Most mercury emitted to the atmosphere since the beginning of the Industrial Revolution has been a result of coal combustion.Elemental mercury(Hg0) is the most common form in the atmosphere, and it can readily transport long distances from the emission sources. Oxidized mercury(Hg2+) is fairly water soluble and is therefore amenable to co-removal in flue gas desulphurization(FGD) scrubbers. Most mercury removal from the atmosphere is in the highly soluble oxidized inorganic form Hg2+.Thus, the oxidation of Hg0 is the key to removal of mercury from flue gas.For the catalysts prepared by traditional impregnation methods, the active componentscannot be well dispersed, leading to low catalytic activity and weak combination between active sites and support.If synthetic Layered double hydroxides(LDHs) precursorsfirst and thenby a roasting processcan get high dispersion of metal oxide catalysts, because LDHs have unique ordered layered structure and lattice orientation effect.In this paper, LDHs precursor was synthesized by coprecipitation method, the composite metal oxide catalysts be obtainedafter the high temperature roasting in the air. The catalyst selected and performance evaluatedin a laboratory scale by simulated flue gas.Using characterization methods such as XRD, XPS, BET, Hg-TPD, H2-TPRand SEM to analysis the structure and performance of catalysts, detailed discusses the mercury oxidation mechanism of metal oxide catalyst and the influence of flue gas composition on the mercury oxidation.The results showed that LDHs derived 1%Mn/Co Al Ox catalyst has excellent catalytic activity on element mercury oxidation, under the high space velocity conditions.On the other hand, the catalyst have wide reaction temperature window and more than 95% efficiency.At the same time, it has good resistance to water and sulfur poison.This kind of catalyst is expected to be put into industrial application in the near future.