Study On The Preparation And De Nox Property Of Low-temperature Mn-Ce/TiO₂ Catalyst In Cement Klin

The emission of NOx from the cement exhaust gas accounted for the total emission of NOx increases year by year. As low-temperature selective catalytic reduction(SCR) of NOx has attracted interests for its high catalytic activity, low amount of injecting ammonia, low operating cost and energy efficiency, it was very suitable for cement industry to control NOx, which was the most promising technology of NOx emission reduction in the cement kiln, catalyst was the core of this technology. However, the activity of low-temperature SCR catalysts could not achieve high efficiency during low-temperature range in the present study, which made the low-temperature SCR technology could not been used to control NOx from cement kiln. In order to solve this problem, the catalytic activity of low-temperature SCR catalyst prepared with TiO2 powder as the support, Mn as the active component and Ce as the active additive was investigated. And then the effect of raction parameters on the catalytic activity of Mn-Ce/TiO2 catalyst was also studied.A series of Mn-Ce/TiO2 catalysts with different active constituents Mn precursor, calcinations temperature, calcinations time and loading amount of active constituents were prepared by step-by-step blended method. It was found that the denitration activity of catalyst with self-made Mn precursor, a calcination temperature of 500 ℃, a calcination time of 4h and ctive constituents loading amount of 16% was the highest. From the characterization of the catalysts by XRD、BET、XPS、SEM and so on, it was fond that the more amorphous MnO2 content in the catalyst, the more helpful to improve the catalytic activity; the lower surface atomic concentration ratio of Mn/Ti(or Mn+Ce/Ti), the less active constituents of the catalyst surface, which was unfavorable for the catalytic activity; The calcinations temperature had more influence on the crystal structure, the surface MnOx valence state and the denitration activity of the Mn-Ce/TiO2 catalyst then he calcination time.In order to study the effect of TiO2 support and TiO2 support doping modification on the denitration activity of Mn-Ce/TiO2 catalyst prepared by step-by-step blended method. From the characterization of the catalysts by XRD、XPS、SEM、BET、TPD、TPR and so on, it was fond that TiO2 support crystal form had little influence on the denitration activity of Mn-Ce/TiO2 catalyst, the low-temeprature activity of this catalyst was not reduced by the synergistic effect of the partial anatase TiO2 prepared by calcination of the catalyst in the preparation of rutile TiO2 catalyst and rutile TiO2; The Mn-Ce/TiO2 catalyst with TiO2 support of larger specific surface area and smaller particle size showed lower denitration activity due to high temperature sintering under the preparation conditions of active constituents loading amount of 16%, calcinations temperature 500℃ and calcination time 4 h; the specific surface area, pore structure parameters, surface pore structure morphology, the low temperature reduction peak area, acid type and acidity of Mn-Ce/TiO2-X catalysts were improved significantly by doping Al2O3 or SiO2 in anatase TiO2 support, the TiO2 crystallinity of Mn-Ce/TiO2-Al2O3 and Mn-Ce/TiO2-SiO2 catalysts were reduced to some extent. All of these were beneficial to improve the denitration activity of catalysts. The denitration activity of catalysts was improved by doping SiO2 and Al2O3 on TiO2 support respectively, the order of SCR denitration NOx activity of three kinds of catalysts above was: Mn-Ce/TiO2-SiO2>Mn-Ce/TiO2-Al2O3>Mn-Ce/TiO2 when the SCR reaction temperature was in the range of 80~150℃.The effect of reaction parameters on Mn-Ce/Ti O2 catalyst was studied. It was found that the denitration activity of Mn-Ce/Ti O2 catalyst decreased with the NO inlet concentration and space velocity increased; the denitration activity of Mn-Ce/TiO2 catalyst rises rapidly when the oxygen concentration was from 1% to 5%, the denitration efficiency stays the same when oxygen concentration was over 5%; the denitration activity of Mn-Ce/TiO2 catalyst reached the best when mole ratio of NH3/NO was 1.0.