Cu/La_2O_3-ZrO_2-Al_2O_3催化剂的制备及其对NO选择性还原的催化性能

Preparation of Cu/La_2O_3-ZrO_2-Al_2O_3 catalyst and its catalytic properties for selective reduction of NO

采用将Al(NO3)3、La(NO3)3和ZrOCl2的混合液滴入沉淀剂(NH4)2CO3中的共沉淀法制备La2O3-ZrO2-Al2O3复合载体,然后负载上Cu2+,制成Cu/La2O3-ZrO2-Al2O3催化剂。考察了该催化剂在富氧条件下对C3H6选择还原NO的催化性能,并借助扫描电子显微镜(SEM)、X射线衍射(XRD)、比表面积测定(BET)、吡啶吸附红外光谱(Py-IR)、程序升温还原(TPR)和热重分析(TG)等方法研究催化剂制备方法与结构、性能的关系。实验结果表明,采用将Al(NO3)3滴入(NH4)2CO3制得的γ-Al2O3能有效地增大催化剂的比表面积,加入La2O3能提高催化剂的热稳定性,加入ZrO2能大幅度增加催化剂表面L酸和B酸的酸量。因此,采用共沉淀法制备的La2O3-ZrO2-Al2O3复合载体能够使Cu/La2O3-ZrO2-Al2O3催化剂具有良好的催化性能,最佳催化活性温度为300℃,NO最大转化率高达88.9%,在有10%水蒸气存在的情况下,仍可达81.9%。

The La2O3-ZrO2-Al2O3 composite support was prepared by co-precipitation method with the mixed aqueous solution of La（ NO3 ）3, Al（ NO3 ）3, and ZrOC12 dropping into the precipitant of （NH4）2CO3 aqueous solution. The Cu/La203-ZrO2-Al2O3 catalyst was prepared by the impregnation of La2O3-ZrO2-Al2O3 with active component Cu^2＋ aqueous solution. The effects of the catalyst on the selective catalytic reduction of NO with propylene in excess oxygen were investigated. The relationships among the preparation method, structure, and properties of the Cu/La203-ZrO2-A1203 catalyst were also explored by means of Scanning electron microscope （SEM） , X-ray diffraction（XRD） , Surface area measurements （BET）, Pyridine absorption infrared spectrum （Py- IR）, Thermalgravimetry （TG）, and Temperature-programmed reduction （TPR）. The results indicate that the support y-Al2O3 prepared by Al （ NO3 ） 3 dropping into （ NH4 ） 2 CO3 can remarkably enlarge the surface area ; the addition of La2O3 contributes mainly to the enhancement of the thermal stability; the introduction of ZrO2 can increase the amount of Lewis and Brφnsterd acid. Consequently, the catalyst Cu/La2O3-ZrO2-Al2O3 has excellent activity for the selective reduction of NO with propylene in excess oxygen. The NO conversion is up to 88.9% at 300 ℃ and 81.9% even at the presence of 10% volume fraction of water vapor.