【作者】 张媛；

【导师】 刘源；

【作者基本信息】 天津大学 ， 工业催化， 2009， 博士

【摘要】 CO优先氧化（CO-PROX）是将用于燃料电池的富氢气体中少量CO脱除至规定要求范围内的重要手段，CO扩散限制是影响CO不能被降至规定ppm级的关键原因。同时作为燃料电池氢源系统的重要组成部分，小型化反应器的开发是核心技术。针对这两个问题，采用有机模板法制备三维有序大孔（3DOM）催化剂和大孔整体式催化剂，通过适当调节催化剂的孔道结构使CO易于扩散和传递，同时采用有机泡沫模板法制备的大孔整体式催化剂具有整体式结构和更高的比表面积/体积比，缩小反应器体积，实现小型化。主要结果如下：以聚苯乙烯（PS）胶晶为模板，采用柠檬酸法制得3DOM CuO-CeO₂催化剂，并将其与破碎大孔结构的催化剂及常规颗粒催化剂在不同空速下进行CO-PROX反应性能测试，发现3DOM CuO-CeO₂催化剂在160,000 mL.gcat^-1.h^-1的高空速下仍能在150～175℃范围内完全转化CO，而破碎大孔结构的催化剂和常规颗粒催化剂在80,000 mL.gcat^-1.h^-1的空速下已不能完全转化CO。这是由于规整排列的连通大孔有利于消除CO扩散限制，提高CO转化率。首次采用向大孔整体式PS泡沫模板中填充水溶胶的方法制备大孔整体式SiO₂和Al₂O₃，该方法制得的大孔整体式除具有有机模板法形状大小和孔道尺寸可调的优点外，还具有溶胶廉价易得、孔隙率高、体积收缩小、孔道相互连通等优点，适用于催化剂载体。前驱物种类、水溶胶浓度、填充次数、添加介孔模板剂、焙烧温度等制备条件均对大孔整体式氧化物的结构有影响，其中以焙烧温度对大孔整体式Al₂O₃的孔结构、晶体结构和机械强度的影响最为显著。在上述大孔整体式Al₂O₃上分别负载CuO-CeO₂和Pt催化剂，考察负载方法和载体制备条件对大孔整体式催化剂结构和性能的影响。在CuO-CeO₂/-Al₂O₃催化剂上，活性组分CuO-CeO₂的负载量对其催化活性有较大影响，负载量较高的催化剂对应的催化活性也较高。在Pt-Ni/-Al₂O₃催化剂上，以Pt（NH3）2（NO₂）2和Ni（NO₃）2.6H₂O为原料，在pH = 7时共同浸渍制得的催化剂具有最佳CO-PROX反应活性。在1vol.% CO、1vol.% O₂、50vol.% H₂、12.5vol.% CO₂、15vol.% H₂O，N₂平衡的反应气氛中，体积空速为20,000 h-1时，能够在160℃将CO含量降低至40 ppm，具有实际应用前景。相比蜂窝整体式催化剂和微反应器，缩小了催化剂的体积，可实现小型化。更多还原

【Abstract】 Preferential oxidation of CO （CO-PROX） is the most promising way for removing CO from H₂-rich gases in fuel cells. It is difficult to reduce the CO content to below the required ppm level due to the diffusive limitation of CO in its oxidation reaction. Furthermore, for CO-PROX, an important part of fuel cell oriented hydrogen production from hydrocarbons, miniaturization is another key challenge. For these two crucial issues, three-dimensionally ordered macroporous （3DOM） catalysts and macroporous monolithic catalysts were prepared via templating method in this work. Properly adjusting the porous structure of the catalysts is favor of CO diffusion and mass transfer. At the same time, the macroporous monolith supports possess monolithic shape and high specific surface area to volume ratio, which are beneficial to compacting reactor volume. Therefore, it is a potential alternative for the miniaturization. The main experimental results and conclusions are as follows:3DOM CuO-CeO₂ catalysts were prepared by using polystyrene （PS） colloidal crystal as the template, nitrate as the precursor and citric acid as the chelator. For CO-PROX reaction, at a higher space velocity of 160,000 mL.gcat^-1.h^-1, complete CO conversion has been obtained between 150 oC and 175 oC. As the macropores of 3DOM are destroyed, complete CO conversion cannot be obtained even at a lower space velocity of 80,000 mL.gcat^-1.h^-1, and likewise over particulate CuO-CeO₂ catalysts. It is proposed that the ordered macropores in the 3DOM catalyst favor mass transfer of CO, resulting in the excellent catalytic performance.Macroporous silica and alumina monoliths have been prepared for the first time by filling polystyrene foam templates with the corresponding hydrosols. The macroscopic shape and macroporous size of the monoliths can be adjusted by the moldable polymer template. Besides, the obtaining macroporous monoliths have the advantages such as cheap and facile raw materials, high porosity, small volume shrinkage and inter-connected macropores, which make them very suitable for using as catalyst supports. The effects of the precursor and the filling times of the alumina hydrosols, the mesopore surfactant addition in the hydrosols and the calcination temperature on the properties of the alumina monolith have been investigated. The characterization results show that the calcination temperature has the most remarkable influence to the porous structure, crystalline phase and compressive strength of the alumina monoliths.CuO-CeO₂ catalysts and Pt-based catalysts were loaded on the macroporous alumina monoliths mentioned above. The influences of the preparation methods and conditions to the catalytic performance were investigated. For macroporous CuO-CeO₂/α-Al₂O₃ monolithic catalysts, the loading amount of the CuO-CeO₂ active component is very important. The monolithic catalysts with higher loading amounts give better catalytic performance for CO-PROX reaction. Among the macroporous Pt-Ni/α-Al₂O₃ monolithic catalysts, excellent performance was observed over the sample prepared via co-impregnating of Pt（NH₃）₂（NO₂）2 and Ni（NO₃）2.6H₂O under pH = 7. At 160 oC and a space velocity of 20,000 h-1, the exit CO content could be reduced to 40 ppm under the reactant feed gas of 1vol.% CO, 1vol.% O₂, 50vol.% H₂,12.5vol.% CO₂, 15vol.% H₂O in N2. Compared to honeycomb monolith and micro-channel catalytic reactor, the volume of the macroporous monolith should be much smaller, indicating that macroporous monolithic catalyst is a potential alternative for CO-PROX compact reactor.更多还原