【作者】 梁皓；

【导师】 刘源；

【作者基本信息】 天津大学 ， 工业催化， 2009， 博士

【摘要】 燃料电池被认为是未来重要的能源设施，因此作为针对燃料电池制氢的重要反应—水煤气变换反应（WGSR）又成为了研究热点。水煤气变换反应是富氢燃料气体处理、净化过程的重要组成部分，不仅可将重整尾气中10¹6%CO的浓度降低到1%以下，而且可以将这部分CO转化成H₂，进一步提高燃料电池系统的效率。负载型Pt基催化剂是最具应用潜力的一种新型水煤气变换催化剂，引起国内外研究者的广泛关注。其中Pt/TiO₂和Pt/CeO₂催化剂具有活性高、稳定性好等特点，颇具研究价值。针对燃料电池制氢需要解决的核心问题是小型化，变换反应器的体积约占碳氢化合物重整制氢系统体积的三分之二，所以变换反应器的小型化至关重要。本工作探索变换反应器小型化的新途径，研究其中的核心技术。本文采用两种模板法分别制备大孔Pt基催化剂和整体式Pt基催化剂，以XRD、TPR、HRTEM、SEM、TG等表征方法对所制备的催化材料进行表征，研究了催化剂性能和结构与性能的关系。主要结果如下：三维有序大孔（3DOM） Pt/TiO₂催化剂在3%CO, 10%H₂O, 87%N₂的气氛中在180³60℃温度区间具有很高的活性，在60,000mL×g^-1×h^-1空速下在250℃时达到平衡转化率，与相同组成的颗粒和介孔催化剂相比，大孔3DOM Pt/TiO₂催化剂表现出更好的催化性能；Pt/TiO₂催化剂反应过程中的活性组分是金属Pt纳米粒子；Pt粒子烧结是Pt/TiO₂催化剂失活的原因；王水处理后催化剂的单位表面金属Pt上的CO转化率升高，在Pt/TiO₂催化剂上的WGSR是个对金属铂结构敏感的反应；通过TPR和HRTEM知道助剂CeO₂通过改变载体与活性组分之间的相互作用来提高催化剂活性。3DOM是实现小型化的途径。采用反相浓乳液法以聚苯乙烯为模板制备了大孔－整体式Pt/CeO₂/Al₂O₃催化剂。通过SEM可以看到孔径在5⁵0μm的不规则大孔，孔径大小可以通过改变分散相体积分数和表面活性剂数量来改变。在模拟重整气条件下的性能测试结果显示，在低温区（180～300℃）单位体积单位时间大孔－整体式Pt/CeO₂/Al₂O₃催化剂上CO的转化量显著高于催化剂上CO转化量。通过比较我们可以发现整体式催化剂在低温区（180～300℃）具有体积小、活性高的特点。将催化剂研制为大孔结构－整体式是实现WGSR反应器体积小型化的很有前景的途径。更多还原

【Abstract】 Water-gas shift （WGS） reaction as a potential pure hydrogen production reaction has recently been attracting rapidly growing interest due to fuel cell power system development, which is considered as a potentially energy source. WGS reaction is a critical process for fuel cell oriented hydrogen production, through which 10¹6%CO can be reduced below 1% and excess H₂ is produced. Supported Pt-based catalysts, especially Pt/TiO₂ and Pt/CeO₂, are promising candidates for WGS reaction owing to their high activity at low-temperature and high stability.The key challenge for fuel cell oriented hydrogen production is the miniaturization of the process, and WGS reactor occupies almost two thirds of the volume in the hydrogen production system from hydrocarbons, so the miniaturization of WGS reactor is of great significance. The aim of this work is to develop novel techniques on WGS reactor miniaturization. Three-dimensionally ordered macroporous （3DOM） Pt/TiO₂ and macroporous - monolith Pt/CeO₂/Al₂O₃ were fabricated by using template method in this work. The so prepared macroporous catalysts were characterized with XRD, TPR, HRTEM, SEM and thermal analysis techniques, and applied to WGS reaction. The relation between catalytic performance and catalyst structure was discussed. The main results and conclusions are as follows:The 3DOM Pt/TiO₂ catalysts exhibited much better catalytic performance than that of both powder and mesoporous Pt/TiO₂ for WGS reaction in 3%CO, 10%H₂O, 87%N₂ feed gases and in the reaction temperature range of 180³60℃, owing to the macroporous structure favoring mass transfer. XPS and catalytic activity results suggested that the active component for the WGS reaction in 3DOM Pt/TiO₂ catalysts was metal Pt which reduced from platinum ions. The results of HRTEM and catalytic stability tests indicated that the sintering of metal Pt particles was the reason for the catalyst deactivation. Chemical adsorption analysis on different 3DOM Pt/TiO₂ catalysts indicated that WGS reaction over the catalysts was structure sensitive. Adding CeO₂ can promote the formation of interaction between Pt and the support. Catalysts with 3DOM structure are potential way to realize the miniaturization of WGS reactor.Macroporous-monoliths of Pt/CeO₂/Al₂O₃ were prepared through inverse concentrated emulsions synthesis route. The macroporous materials exhibited a bimodal meso-macroporosity with macropores in size of 5⁵0μm, as shown in SEM images. The pore size can be adjusted by the volume fraction of dispersed phase and the amount of surfactant added. The macroporous monolith Pt/CeO₂/Al₂O₃ exhibited better catalytic performance that that of micro-channel Pt/CeO₂/Al₂O₃ catalyst for WGS reaction in simulating reformate gases. The converted amount of CO over monolith Pt/CeO₂/Al₂O₃ was much higher than that over micro-channel Pt/CeO₂/Al₂O₃ on per volume of catalysts, showing that the catalysts of the macroporous monolith are promising and much potential materials for the miniaturization of WGS reactor.更多还原