来源：塑料托盘 发布时间：2010年7月19日
塑料托盘甲醇重整制氢技术是解决质子交换膜燃料电池(PEMFC)移动氢源最可行的途径之一。由于微量CO就容易引起PEMFC的电极PtRu催化剂中毒,因此,脱除甲醇重整氢气中CO对PEMFC的应用十分重要。研究表明,CO选择性氧化反应是脱除塑料托盘甲醇重整气中CO最有效的方法。本文目的是研制蜂窝陶瓷整体催化剂,选择性氧化脱除甲醇重整气中CO至PtRu催化剂能够承受的浓度范围(<50 ppm)。结果表明,Pt/Al_2O_3整体催化剂能够有效地选择性氧化脱除CO。同时,助剂的影响研究表明,Co助剂明显地提高了Pt/Al_2O_3整体催化剂的活性和CO选择性,同时拓宽了催化剂的活性温度区间,并使其向低温移动。系统地考察了反应温度、氧碳摩尔比、H_2O、CO_2、体积空速、CO浓度、塑料托盘H_2浓度、滞后现象等因素,以及H_2氧化反应、CO水蒸汽逆变换反应和甲烷化等副反应对Pt/Al_2O_3整体催化剂选择性氧化脱除CO效果的影响,最后得出最优的反应操作条件。提出了Pt/Al_2O_3整体催化剂选择性氧化脱除CO反应机理和动力学模型,实验得出反应动力学方程参数,在此基础上建立数学模型,数值模拟催化剂床层浓度场和温度场分布。同时设计平塑料托盘板反应器,实验研究了催化剂床层浓度场和温度场分布,并与数值模拟结果进行比较。在实验和理论的基础上,将Pt/Al_2O_3整体催化剂放大应用于5kW甲醇自热重整氢源系统,选择性氧化脱除CO。产品气中CO浓度满足PEMFC的要求,系统与PEMFC成功联试。【Abstract】 Hydrogen production from methanol reforming is one of the most promising approach for proton exchange membrane fuel cells (PEMFCs). Due to the strong chemisorption on the anode PtRu catalyst surface, trace CO will dramatically depress the performance of PEMFC. It is very essential to clean up CO from methanol reformate for PEMFC applications. Research showed that selective CO oxidation is the most effective and economic method to reduce CO down to 50 ppm level, which can be tolerated by the PtRu catalyst.This paper prepared monolithic honeycomb catalysts which could selectively oxidize CO down to 50 ppm level from methanol reformate. The catalysts with Pt, Pd, Ru, Rh supported on Al_2O_3 were studied and Pt was the best. Further investigation showed that doping Co in Pt/Al_2O_3 could improve CO conversion and selectivity, broaden its reaction temperature window and shift it down to low temperature.Effects of various operation parameters on selective CO oxidation was systematically stud.ied over Pt/Al_2O_3 catalyst, including temperature, molar ratio of O2 to CO, H_2O, CO_2, space velocity, CO concentration, H_2 concentration and hysteresis phenomena. Effects of side reactions, including H_2 oxidation, CO reverse water-gas-shift reaction (rWGS) and methanation, were also investigated. Then the optimal operation conditions were obtained.The reaction mechanism of selective CO oxidation over Pt/Al_2O_3 was launched. All parameters in the kinetic models, which described CO oxidation and H_2 oxidation, were obtained.