Preparation Of MnO_x-TiO₂Catalysts And Their Catalytic Properties For Chlorobenzene Combustion

Dioxins (polychlorinated dibenzo-p-dioxins and dibenzofurans, PCDD/Fs) are typical persistent organic pollutants (POPs), and nowadays, they attracted the world’s attention broadly because of their high toxicity. In recent years, many methods have been developed to remove dioxins. Among them, catalytic combustion has the advantages of low-temperature operation, low costs and no by-products, and it is considered to be one of the most promising technologies for the removal of dioxins. Among all kinds of catalysts, Mn/Ti system is widely employed in dioxins catalytic oxidation because of its high activities and nontoxicity. Mn tends to be poisoned in the catalytic oxidation of dioxins, thus Mn/Ti system is greatly limited in the industrialization. Aiming at this problem, the following work has been done:1. A series of MnOx-TiO2catalysts with different Mn content was prepared by homogeneous precipitation and the catalyst with appropriate Mn/Ti proportion was chosen as the target catalyst to study the resistance to chlorine poisoning of the Mn-containing catalyst.9samples with different Mn content were prepared and we found that the catalysts were solid solution with the matrix of anatase TiO2when the molar ratio of Mn and Ti is less than1:3. When the Mn content continued to increase, the manganese oxide crystals occurred. We select the catalyst, in which the molar ratio between Mn and Ti is1:3, as the research object, because the crystal structure of solid solution is simple and this selection can simplify the following study greatly. Moreover, the content of Mn is considerable and the subsequent experimental phenomenon is noticeable.2. A series of SnOx-MnOx-TiO2catalysts with different Sn content was prepared by homogeneous precipitation, and appropriate amount of Sn was determined. The resistance to chlorine poisoning of MnOx-TiO2and SnOx-MnOx-TiO2catalysts at different temperatures was studied.When the Sn content is lower than10%, the activity of catalyst is barely changed. The MnOx-TiO2catalyst with10%Sn was chose as the object to study, and the stability of MnOx-TiO2and SnOx-MnOx-TiO2catalysts at different temperatures, namely the resistance to chlorine poisoning in this artical, was studied. The results indicated that the addition of Sn can enhance the ability to remove the adsorbed Cl species and inhibit the formation of MnOxCly, which is related to its high resistance to chlorine poisoning. The temperatures which were needed to keep stable activity for SnOx-MnOx-TiO2and MnOx-TiO2catalysts are225℃and300℃, respectively.