【作者】 张勇；

【导师】 林性贻；

【作者基本信息】 福州大学 ， 工业催化， 2014， 硕士

【摘要】 面对愈来愈严重的能源短缺问题,亟待开发新的能源。和传统的石化燃料相比,氢能具有能量高、无毒和可再生等优点,是一种极为优越的新能源,因而倍受科学家青睐。目前,H2主要来源于天然气重整及煤气化等,然而这些重整产物中不可避免含有一定量的CO,它会使燃料电池Pt电极中毒失效。水煤气变换反应(WGSR)在降低CO的含量的同时又能产生H2,随着燃料电池技术的兴起,WGSR催化剂再次引起了科学家的关注。传统的水煤气变换催化剂因热稳定性差,硫化过程繁琐,无法满足燃料电池的需要,迫切需要开发新型的水煤气变换催化剂。因此,本论文选择价廉、易得,且变换催化性能良好的铜铁催化剂为研究对象。本文制备了一系列的Cu/Fe3O4催化剂,通过N2-物理吸附，XRD、H2-TPR、CO2-TPD、 O2-TPO、Raman、SEM、N2O-desorption、CV等技术手段研究了催化剂的结构、物化性能及表面性质对催化活性的影响,探讨催化剂的结构与性能之间的关系。首先,考察了不同沉淀剂(KOH、K2CO3、Na2CO3、NAOH和NaHCO3)制备的系列Cu/Fe3O4催化剂的结构和变换性能。结果发现,以KOH为沉淀剂制备的催化剂表现出较好的变换性能,这与其具有较大的比表面积,更高的Cu分散度,最多的弱碱性活性位点和更强的铜铁协同作用力密切相关。其次,通过添加助剂(ZnO)对Cu/Fe3O4催化剂进行改性研究。以KOH为沉淀剂,采用分步共沉淀法制备了一系列的Cu/Fe3O4-ZnO催化剂。结果表明：添加2.5 wt.% ZnO改性的催化剂具有更好的Cu分散性,提高了催化剂的还原性能；含有更多较弱的或是中强的碱性活性位点,有利于H2O的解离和CO的吸附,其催化剂活性和热稳定性较佳。此外,通过添加助剂(La203)对Cu/Fe3O4催化剂进行改性研究。La203助剂的引入减弱了铜铁之间的相互作用,抑制了CuFe2O4的生成,减少了可被还原的活性铜物种的数量,削弱了催化剂的还原性能,降低了催化剂的变换性能。更多还原

【Abstract】 It is extremely urgent that we need to develop new sources of energy to solve the serious shortage problem of energy. Compared with traditional fossil fuels, hydrogen energy has attracted the scientists’ attention due to its high energy, non-toxic, renewable, etc. Nowadays, the production of hydrogen is mainly based on the catalytic steam reforming of natural gas, coal gasification and so on. However, The reformed fuel contains a bit of CO, which may degrade the performance of the Pt electrode. With the development of fuel cell, water-gas shift catalysts have aroused the interest of scientists because of its removal of CO and production of H2 simutaneously in the water-gas shift reaction (WGSR). Whereas,Traditional WGS catalysts can not meet the needs of the fuel cell because of their disadvantage such as poor thermal stability, tedious vulcanization process, etc. It is essential to develop new WGS catalysts. Therefore, the Cu/Fe3O4 WGS catalysts were employed as research objects due to their low costs as well as good catalytic performance in this work.In this present work, we obtained a series of Cu/Fe3O4 WGS catalysts. The catalytic performance, which affected by structure of the catalyst, physico-chemical properties and surface properties, was investigated by N2-physisorption, XRD, H2-TPR, CO2-TPD, O2-TPO, Raman, SEM and N2O decomposition.Firstly, we investigated the effect of different precipitants (KOH, K2CO3, Na2CO3, NaOH, and NaHC03) on the structure and activity of Cu/Fe3O4 catalysts. The result shows that the catalyst prepared by the KOH exhibit much better activity. It is suggested that higher Cu dispersion, larger BET surface area, larger amount of weak basic sites, and strong synergistic interaction between copper and iron oxides are responsible for the high catalytic performance.Secondly, the dopant (ZnO) was added to modify the Cu/Fe3O4 WGS catalysts. We synthesized a series of Cu/Fe3O4-ZnO catalysts by stepwise precipitation with KOH as precipitant. The result shows that the modified catalyst (2.5 wt.% ZnO) can improve reducibility due to its higher Cu dispersion. Moreover, it can promote dissociation of H2O and adsorption of CO because of its larger amount of weak or medium basic sites. Hence, Cu/Fe-Zn2.5 performs better activity and thermal stability.In addition, the dopant (Le2O3) was added to modify the Cu/Fe3O4 WGS catalysts. However, the addition of La2O3 reduces the interaction between copper and iron oxide, refrains the production of main phase of CuFe2O4, results in the declining of amount of active copper species. It weakens the reductive performance and catalytic activity of catalysts.更多还原