络合-溶剂热法制备钯基催化剂及其催化氧化间二甲苯性能

摘要

通过采用络合-溶剂热法、水热法和浸渍法三种方法制备了负载量为0.6％(质量分数)的Pd/Al2O3催化剂,重点考察不同制备方法催化氧化间二甲苯作为典型的挥发性有机化合物的能力.结果表明:络合-溶剂热法制备的Pd/Al2O3-com催化剂催化氧化间二甲苯的能力最强,间二甲苯体积分数为0.002％时完全转化温度(T100)为130℃,低于浸渍法制备催化剂的完全转化温度30℃.对Pd/Al2O3催化剂进行了比表面积(BET)、X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)等表征分析,发现Pd/Al2O3-com中Pd主要以还原态Pd0高度分散于载体表面,而另两种方法制备的催化剂均有明显的Pd2+存在.结合性能测试及表征分析,表明络合-溶剂热法制备的Pd/Al2O3-com催化剂活性组分Pd的高度分散,增强了催化活性,可满足高浓度间二甲苯、宽气体体积空速条件下催化氧化脱除间二甲苯的工业应用要求.%The Pd/Al2O3 catalysts with a loading of 0.6％ (mass fraction) were prepared by complexation-solvent thermal method, hydrothermal method and impregnation method. The effect of different preparation methods on the performance of the catalyst was evaluated by using m-xylene as the representative of volatile organic compounds (VOCs). The results showed that the most effective catalyst Pd/Al2O3-com was prepared by complexingsolvothermal.The m-xylene with volume fraction of 0.002％ can completely converted to CO2 and H20 (T100) at130℃ over Pd/Al2O3-com catalyst from the complexing-solvothermal method, which was lower about 30℃ than the catalyst (Pd/Al2O3-imp) from the impregnation method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) techniques were performed to characterize the physio-chemical properties of synthesized Pd/Al2O3 catalysts. The results indicated that the Pd element of Pd/Al2O3-com was mainly dispersed on the surface of the support at the reduction state Pd0, while the Pd element of Pd/Al2O3-imp and Pd/Al2O3-hyd catalyst was at the form of Pd2+ with poor dispersion. Combined with the catalytic activity performance and evaluation results, a highly dispersed and reduction state form of Pd active component on the surface of the carrier resulted in a remarkable catalytic activity on m-xylene conversion. The Pd/Al2O3-com catalyst with these features exhibit good activity for removing VOCs under high concentration (0.02％-0.07％, vol) and wide space velocity (5×104-10×104 h-1) conditions, and thus meet well the requirements of industrial application.