【作者】 张玲玲；

【导师】 董林；

【作者基本信息】 南京大学 ， 物理化学， 2011， 博士

【摘要】 第一部分通过XRD、Raman、XPS、UV-vis DRS、FTIR、H2-TPR、O2-TPD和CO+O2模型反应系统研究了前驱体(醋酸钴和硝酸钴)对氮气气氛下焙烧CoOx/γ-A2O3催化剂组成、分散、还原以及催化性质的影响,得到以下结论：1、以醋酸钴和硝酸钴为前驱体分别制得CoO/yγ-Al2O3和Co3O4/γ-Al2O3催化剂。而且CoO能高度分散在γ-Al2O3载体表面形成四面体配位单层,其分散容量为1.50 mmol/(100 m2 γ-Al2O3);而Co3O4易在载体表面聚集成晶体,其分散容量仅为0.15 mmol/(100 m2 γ-Al2O3)。2、在钴负载量低于1.2 mmol/(100 m2 γ-Al2O3)时,CoO/γ-Al2O3催化剂对CO的催化活性高于相同负载量的Co3O4/γ-Al2O3催化剂。CoO/γ-Al2O3催化剂中分散态的CoO难被还原但很易吸附氧物种,是CO氧化的主要活性物种。Co3O4/γ-Al2O3催化剂中晶相Co3O4是CO氧化的主要活性物种,它在低温下易被还原但难吸附氧物种。3、提出了CoO在γ-Al2O3表面分散的嵌入模型,用于解释CoO/γ-Al2O3催化剂的分散及还原性质。第二部分通过XRD、Raman、XPS、UV-vis DRS、H2-TPR、NO+CO模型反应和原位FTIR系统研究了前驱体(醋酸钴和硝酸钴)对空气气氛下焙烧CoOx/γ-Al2O3催化剂组成、分散、还原以及催化性质的影响,得到以下结论：1、钴负载量较低(02Co(A)/Al和01Co(N)/Al)时,氧化钻主要以Co2+离子形式进入γ-Al2O3表面的四面体空位,该物种在700℃以下难被还原。2、随着钴负载量的增加,以醋酸钴为前驱体制备的CoOx/γ-Al2O3催化剂,在载体表面氧化钴主要以分散和团簇C0304的形式存在。该物种在320-340。C很容易被还原成Co2+离子,对NO+CO反应具有很好的催化活性。继续增加钴负载量到1.80mmol/(100m2 γ-Al2O3)时,由于晶相C0304颗粒变大,其催化性质反而降低,表明Co(A)/Al样品中分散和团簇C0304是主要的活性物种。3、以硝酸钴为前驱体制备的CoOx/γ-Al2O3催化剂,随着钴负载量的增加,晶相C0304晶格缺陷增多,还原温度由400。C降至360。C,催化活性逐渐升高,表明晶相C0304是主要的活性物种,晶格缺陷的增多是其活性提高的主要原因之一。4、以醋酸钴为前驱体制备的CoOx/γ-Al2O3催化剂的催化活性高于相同负载量的以硝酸钻为前驱体制备的CoOx/γ-Al2O3催化剂,这与活性物种的分散和还原性质有关。第三部分以不同的铜钴前驱体(醋酸和硝酸盐)采用共浸渍法制备CuO-CoOx/γ-Al2O3催化剂,并通过XRD、Raman、XPS、H2-TPR、NO+CO模型反应和原位FTIR对催化剂的结构和性质进行了表征,系统研究了前驱体对CuO-CoOx/γ-Al2O3催化剂结构和性质的影响,得到以下结论：1、对于CuACoA/Al催化剂,负载的CuO和CoOx两组份分离,CuO在载体表面发生部分聚集,而CoOx主要分散在载体表面。其主要活性物种是CuO。2、对于CuNCoN/Al催化剂,负载的CuO和CoOx发生强相互作用形成了晶相态的CuxCo3-xO4(x<4)尖晶石,其余负载CuO分散在载体表面。其主要活性物种是分散态的CuO和表面CuxCo3-xO4(x<1)尖晶石。3、对于CuNCoA/Al催化剂,负载的CuO和CoOx能均匀地分散在载体γ-Al2O3表面,且二者之间存在协同效应,有利于促进催化剂表面氧的还原和NO+CO反应性能的提高。原位红外结果表明分散态CuO和CoOx之间的协同效应很容易促进NO的分解和铜物种的还原,因此CuNCoA/Al催化剂表现出最好的NO还原活性。更多还原

【Abstract】 Part Ⅰ:The effect of cobalt precursors (cobalt acetate and cobalt nitrate) on the compostion, dispersion, reduction, and catalytic properties of CoOx/γ-Al2O3 catalysts calcined in N2 was tentatively investigated. XRD, Raman, XPS, FTIR, UV-vis DRS, H2-TPR, O2-TPD, and CO+O2 model reaction were used to characterize the catalysts. The following conclusions could be drawn:1. It is found that CoO/γ-Al2O3 and Co3O4/γ-Al2O3 catalysts are formed from the precursors of cobalt acetate and cobalt nitrate, respectively. In addition, CoO can be highly dispersed to form a tetrahedral-coordinated monolayer with its dispersion capacity of 1.50 mmol/(100 m2 γ-Al2O3). But Co3O4 tends to agglomerate above its dispersion capacity of 0.15 mmol/(100 m2 γ-Al2O3).2. CoO/γ-Al2O3 catalysts are more active than the corresponding Co3O4/γ-Al2O3 catalysts for CO oxidation at cobalt loading amount≤1.2 mmol/(100 m2 γ-Al2O3). The main active species is dispersed CoO for CoO/γ-Al2O3 catalysts, which is difficult to be reduced and easy to desorb O2-(ad) species that participates in CO oxidation. But the main active species is crystalline Co3O4 for Co3O4/γ-Al2O3 catalysts, which is difficult to desorb oxygen species and easy to be reduced at low temperature.3. A surface incorporation model was proposed to explain the dispersion and reduction properties of CoO/γ-Al2O3 catalysts.Part II:The effect of cobalt precursors (cobalt acetate and cobalt nitrate) on the compostion, dispersion, reduction, and catalytic properties of CoOx/γ-Al2O3 catalysts calcined in air was tentatively investigated. XRD, Raman, XPS, UV-vis DRS, H2-TPR, NO+CO model reaction and in situ FTIR were used to characterize the catalysts. The following conclusions could be drawn:1. It is found that at lower cobalt loading amounts (02Co(A)/Al and 01Co(N)/Al), supported cobalt oxide mainly exists as Co2+ions in the tetrahedral sites of γ-Al2O3, which is difficult to be reduced below 700℃.2. With the increase of cobalt loading amount, cobalt oxide mainly exists as dispersed Co3O4 and Co3O4 cluster on γ-Al2O3 for CoOx/γ-Al2O3 catalysts from cobalt acetate precursor. This species is easy to be reduced to Co2+ions at about 320-340℃ and shows high activity for NO+CO reaction. Further increase the cobalt loading amount to 1.80 mmol/(100 m2 γ-Al2O3), the size of crystalline Co3O4 becomes large and its activity decreases, which indicates that the dispersed Co3O4 and Co3O4 cluster are the main active species.3. For CoOx/γ-Al2O3 catalysts from cobalt nitrate precursor, with the increase of cobalt loading amount, the crystal defect of crystalline Co3O4 increases, its reduction temperature decreases from 400℃ to 360℃ and its activity for NO+CO reaction increases. The results indicate that crystalline Co3O4 is the main active species, probably the crystal defect sites are the mainly active sites.4. With the same cobalt loading amount, the catalytic activities of CoOx/γ-Al2O3 catalysts are higher from cobalt acetate precursor than from cobalt nitrate precursor, which are probably related to the reduction and dispersion properties of the active species.Part III:The effect of precursors on the structure and catalytic property of CuO-CoOx/γ-Al2O3 catalysts prepared by co-impregnation with different copper and cobalt precursors (acetate or nitrate salts) was tentatively investigated. XRD, Raman, XPS, H2-TPR, NO+CO model reaction, and in situ FTIR were used to characterize the catalysts. The following conclusions could be drawn:1. For CuACoA/Al catalyst, supported copper oxide and cobalt oxide are segregated, copper oxide from copper acetate precursor agglomerated and cobalt oxide from cobalt acetate precursor dispersed on γ-Al2O3. The main active species are agglomerated copper oxide.2. For CuNCoN/Al catalyst, supported copper oxide and cobalt oxide interact strongly with each other and CuxCo3-xO4 (x<1) spinel is formed and agglomerated, the rest of copper oxide exists as dispersed state. The main active species are dispersed copper oxide and crystalline CuxCo3-xO4 (x<1) spinel.3. For CuNCoA/Al catalyst, supported copper oxide and cobalt oxide could be homogeneously dispersed. There is an interfacial synergism of copper oxide and cobalt oxide, which is facile for NO reduction and CO oxidation. In situ FTIR results reveal the synergistic effect between dispersed copper oxide and cobalt oxide can promote the reduction of the catalyst by CO and the dissociation of NO, which is the reason for its highest activity for NO reduction by CO.更多还原