Reserch On The Preparation Of MnO_x/HNTs Catalyst By In-situ Method And The Low Temperature SCR Denitration Properities

Selective catalytic reduction of NOx with NH3 had proved to be a reliable and efficient way to control NOx emission, especially for stationary sources such as power boilers and combustion furnaces. In recent researches,Manganese based catalysts had been applied and exhibited excellent activity in low-temperature SCR reactions, but the actually low-temperature SCR activity (especially below 150℃ or even lower) for most catalysts remained unsatisfactory. Meanwhile, an accumulating number of researchers focused on the attempt of the nanocrystallization of catalyst carriers,mainly CNTs and titania nanotubes. But, the use of HNTs which is also characterized for a hollow nanotube structure as the support for manganese oxides has not yet been investigated. In this paper, Halloysite (HNTs) was firstly adopted as a carrier to develop manganese based SCR catalysts (MnOx/HNTs).Firstly, to improve the dispersion of active component in the catalysts, a mild in-situ deposition method operated at room temperature was introduced. From the comparion of catalysts prepared by in-situ deposition, dipping, coprecipitation methods, it was found that the hollow nanotube structure and highly dispersion of manganese oxides (MnOx) of catalysts prepared by in-situ deposition method were leading to the perfectly activity. Therefore, for the adoption of halloysite as carrier,in-situ deposition method was a potential one to prepare low-temperature SCR catalyst.Secondly, base on the catalysts prepared by in-situ deposition method, the operating parameters were investigated, including the ratio of Mn(AC)2 /KMnO4, Mn loading,space velocities, long-acting, sulfur tolerance. Furthermore, the thermal stability and structure study of the catalyst was carried out by TG and TEM. It was reasonably deduced that the MnOx particles prepared by a mild in-situ deposition method are successfully fabricated and well dispersed on both internal and external surface of HNTs in nano scale.At last, the reaction process and the mechanism were studied by H2-TPR and TPD.It was indicated that the main phases of NH3 was coordinated NH3 and NH4+, mainly NH4+, both of them would react with adsorptive NO. Besides, the main routine of the SCR reaction on catalysts belonged to L-H mechanism.