Rh/Al_2O_3-Cr_2O_3整体式催化剂的制备和二氯甲烷催化氧化性能

Preparation of Rh/Al_2O_3-Cr_2O_3 Monolithic Catalysts for Dichloromethane Combustion

以粉末Al_2O_3为载体,通过浸渍Rh(NO_3)_3制备Rh/Al_2O_3催化剂;再以Rh/Al_2O_3、粉末Cr_2O_3和铝胶经过研磨混合制得催化剂活性浆料;将催化剂活性浆料涂覆到堇青石蜂窝陶瓷载体表面,经烘干,焙烧制得不同Rh含量的Rh/Al_2O_3-Cr_2O_3系列整体式催化剂.研究了该类催化剂的二氯甲烷催化氧化性能,发现Rh负载量为0.4 g/L的Rh/Al_2O_3-Cr_2O_3催化剂活性最佳,且未生成含氯中间产物.结合催化剂的表征结果发现,Rh的添加可增加催化剂的表面酸性和氧化还原性能,二者的协同作用提高了催化剂活性;而Cr_2O_3的存在有利于CH_3Cl中间体的进一步氧化,从而提高了催化剂的选择性.

A series of Rh catalysts supported on Al2O3 powder was prepared by impregnation method. Then a series of Rh/Al2O3-Cr2O3 monolithic catalysts was prepared by coating method, different proportions of Rh/Al2O3,Cr2O3 and aluminum gel were mixed into a homogeneous slurry,and then was coated onto the cordierite honeycomb ceramic. These catalysts with different Rh contents were tested for catalytic combustion of dichloromethane. It was found that the 0. 4 Rh/Al2O3-Cr2O3（ Rh contents： 0. 4 g/L） had the highest activity and no chlorine-containing by-products were formed. The catalysts were characterized by various techniques such as XRD,H2-TPR,NH3-TPD and BET. The results showed that the addition of Rh can improve the surface acidity and redox performance of the catalyst,and further improve the activity of the catalyst. It was believed that the activity of the catalyst was closely related to its reducibility and surface acidity. Moreover,the addition of Cr2O3 is beneficial to the further oxidation of CH3Cl intermediate and thus improve the selectivity.