摘要
用浸渍法和共沉淀法分别制得CuO-ZrO2复合氧化物具有不同的选择还原NOx的催化性能.采用XRD,BET,EXAFS和H2-TPR等手段对样品进行了表征.发现浸渍法制备的样品具有的比表面较大,氧化锆被稳定在四方相.EXAFS实验表明,浸渍法制得样品的铜离子填入氧化锆表面空穴中,并以Cu+形式存在;而500℃焙烧条件下用共沉淀法引入的铜离子可部分取代锆离子,在氧化锆体相高度分散形成均匀的无定形固溶体.铜离子在氧化锆体相的高度分散是形成表面孤立铜物种的关键.溶入氧化锆体相的铜离子在取代部位由于局部负电荷而使氧化性降低,是共沉淀法制备样品具有较高催化活性的主要原因.
Different catalytic performances of CuO - ZrO2 mixed oxides prepared by impregnation or co precipitation method for selective reduction of NO tin the presence of O-2 were investigated. The structures and properties of the catalysts were characterized Ly XRD, BET surface area measurement, EXAFS and H-2 - TPR measurements. The CuO - ZrO2 mixed oxides prepared by impregnation method had larger surface area than those prepared by co - precipitation method. The zirconium oxide was stabilized at the tetragonal phase. EXAFS measurement shows that in the CuO - ZrO2 mixed oxides prepared by impregnation method the copper ions first fill in the surface hole of zirconium oxide and stay there as Cu+. Under the calcination at 500 degreesC, the Cu2+ ions that brought into ZrO2 by co- precipitation method carl replace Zr4+ and form a uniform amorphous solid solution. The high -dispersion of Cu ions in zirconium oxide was the key element that led to formation of highly dispersed isolated copper species on the surface. Substitution of Zr4+ by Cu2+ ions could decrease the reducibility of copper species and the activity of the complete oxidation of propene. The local structure difference of copper species was the main reason for the high activity and selectivity of the CuO - ZrO2 mixed oxides prepared by co - precipitation method.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2001年第5期713-717,共5页
Acta Chimica Sinica
基金
国家重点基础研究发展计划(973计划)，国家自然科学基金
