MnOx/TiO2催化剂的制备及其低温NH3选择性催化还原NO性能

为了研究MnOx/TiO2催化剂的低温催化还原NO性能,采用微乳液法在不同的煅烧温度下制备了不同晶相的纳米TiO2,并以此为载体,利用浸渍法制备了一系列MnOx/TiO2催化剂.然后,利用BET,XRD,HRTEM,H2-TPR等方法研究了载体和催化剂的微观结构、分散状态和氧化还原性质.实验结果表明:随着煅烧温度的增加,纳米TiO2从锐钛型逐渐向金红石型转变,700℃煅烧得到的纳米TiO2呈混晶相,800℃煅烧得到的纳米TiO2则为纯金红石型；锐钛型及混晶相TiO2载体与活性氧化物MnOx之间的相互作用较为强烈,当纳米TiO2中金红石型与锐钛型并存时,MnOx优先与锐钛型纳米TiO2作用；纯金红石型纳米TiO2与MnOx之间的相互作用较弱.模拟NH3选择性催化还原NO的反应活性测试结果表明,500℃煅烧得到的MnOx/TiO2催化剂表现出较高的低温活性.

Preparation of MnOx/TiO2 catalyst and catalytic performance for selective catalytic reduction of NO with NH3 at low temperature

To study the MnOx/TiO2 catalyst’s catalytic performance for selective catalytic reduction of NO with NH3 at low temperature,TiO2 nanoparticles with different crystalline phases are prepared by the micro-emulsion method at different calcination temperatures.A series of MnOx/TiO2are prepared by impregnation with TiO2 nanoparticles and manganous acetate precursor.Then the micro-structures,dispersion status and redox properties of the product are characterized by BET,X-ray diffraction,high-resolution transmission electron microscopy,and H2-temperature programmed reduction.The experimental results show that with the increase of the calcination temperature,the anatase TiO2 transfers to the rutile TiO2.When the calcination temperature is 700℃,the anatase-rutile mixture of TiO2 nanoparticles is formed;when the calcination temperature is 800℃,the pure rutile TiO2 occurs.The anatase TiO2 and the anatase-rutile mixtures have a stronger reaction with MnOx than the rutile TiO2.MnOx can react firstly with the anatase TiO2 and then with the rutile TiO2.The catalyst test results of selective catalytic reduction of NO with NH3 show that the MnOx/TiO2 catalyst calcined at 500℃ has a high activity at low temperature.