蓄热型甲烷燃烧催化剂的构筑及其蓄热-催化耦合效应

Coalbed gas resources are very rich in China and most of them contain lean methane. Catalytic combustion of lean methane for powder or heat generation is a very important technology, because it shows a strong demonstration effect to the efficient utilization of other low grade energy. It is well known that there is a structural problem between the autothermal operation and the outside utilization of heat in the catalytic combustion system, and the runaway on catalyst bed is hard to avoid during the combustion process. In this case, we proposed to combine the phase change materials and catalyst, obtaining a thermal storage functional catalyst with high thermal storage density. By using the phase change thermal storage technology, the stability and uniformity of the temperature in the catalyst bed will be improved and the autothermal operation and the outside utilization of heat will be more maneuverable. Finally, the high efficient on the lean methane combustion and subsequent heat utilization can be achieved. Based on the above discussions, this project mainly focuses on the control of size, structure and catalytic-thermal storage dual function of the catalysts, the role and interaction of microstructure, phase change material infiltrating layer and catalytic interface during the combustion process, and the coupling effect between catalysis and thermal storage function. The structural, physicochemical and thermal properties of different catalyst will be characterized in detail, and the results can be related to the catalytic and thermal storage performance in the catalytic process. The heat and mass transfer in the CRFF reactor will also be investigated. Combining with the numerical simulation, the new linkage models among catalysis, thermal storage and heat utilization during the combustion process will be discussed. It is reasonable to believe that the implementation of this project will improve the efficiency of the lean methane utilization, and it could also show good references for solving the problems in fixed bed reactors, such as the temperature runaway and the formation of hot-pot in catalyst bed.

煤层气中蕴藏巨量的低浓度甲烷，其催化燃烧制热或发电技术对低品位能源的高效利用有重要的示范作用。项目针对低浓度甲烷催化燃烧系统自热运行与供热间的结构性矛盾和催化剂床层飞温等现象，提出将相变蓄热材料耦合于催化剂中，构筑高蓄热密度的蓄热型催化剂，以改善床层热环境，扩大系统自热运行与供热环节的操作空间，提升燃烧及供热效率。项目拟以核壳结构蓄热型催化剂的制备为先导，围绕催化-蓄热双功能材料的尺度、结构及功能调控手段；相变材料特殊浸润层和催化界面的相互作用机制；以及催化剂服役过程中材料蓄放热特性与催化功能的动态耦合特征等关键科学问题开展研究，通过对逆流反应器中的催化过程热质传递行为的系统考察，探讨低浓度甲烷燃烧过程中催化、储能与用能联动的新模式和规律。项目的实施不仅对于低浓度甲烷资源的高效利用有重要意义，对广泛存在于固定床反应系统中的催化剂床层温度不稳、易出现热点等问题的解决亦有一定的普适性。

蓄热型催化剂能够实现煤矿乏风低品位能源的高效转化。项目以Al基核壳结构蓄热型催化剂的制备为先导，通过调控催化-蓄热材料的结构与双功能，构筑具有不同适应性的高效蓄热型催化剂，并探讨了其结构特征和组分优化对蓄放热性能、结构稳定性和催化活性的影响规律，探明了CH4在催化剂上的催化转化机理和催化剂微结构动态变化过程，同时借助Fluent数值模拟研究了低浓度甲烷蓄热催化燃烧过程传热传质特性。主要研究成果有：①优化了课题组前期提出的合成核壳结构Al@Al2O3复合相变蓄热材料制备方法，形成了层状壳层及yolk结构，提高了壳层的弹性，为相变材料熔融过程的体积膨胀提供了空间，100次循环材料破损率仅为3.5%。②设计了一种甲烷催化裂解法制备Al@Al2O3-C复合相变蓄热材料的新方法，形成的碳纤维积碳层可强化壳层的致密度和导热性（导热系数提升3-5.3倍），并进一步提升蓄热型催化剂的结构稳定性、机械性能和吸放热循环稳定性。③首次制备了Co3O4/(SiAl@Al2O3)蓄热型催化剂并应用于低浓度甲烷催化燃烧，利用铝硅合金熔点可调且与甲烷燃烧温度匹配的特点，解决了催化燃烧过程中固定床反应器存在的热点和飞温等问题，同时增强了甲烷转化率（T90=370℃）和热量利用效率；④制备了系列铈基固溶体型（Ce-Fe-O）、尖晶石型（MnCo2O4/SiC）和钙钛矿型（LaCoO3、LaFeO3等）催化剂，详细研究了其催化甲烷燃烧性能，阐明了催化剂比表面积、晶格畸变程度、氧空位浓度、表面物种等因素对甲烷催化燃烧性能的影响规律，探讨了甲烷燃烧反应的反应路径，并分析了杂质元素（硫、水蒸气）对催化剂活性和稳定性的影响机制，开发了高抗硫性非贵金属催化剂（MnCo2O4/SiC）；⑤利用数值模拟探究了蓄热型催化剂颗粒大小、预热温度、入口流速等工况参数对催化剂床层热结构、甲烷转化率、反应器温度分布和自热运行条件等的作用规律，结果表明小粒径有利于颗粒相变，增加入口流速有助于组分扩散与能量传递提升相变速度。项目的实施为低浓度甲烷燃烧过程中催化、储能与用能联动以及功能化催化剂设计提供了一定的理论和实践支撑。.项目负责人李孔斋入选教育部长江学者奖励计划”青年学者、云南省政府特殊津贴获得者、云南省中青年学术和技术带头人、全球顶尖科学家数据库等，获云南省自然科学特等奖1项（排名第二）和“云南青年五四奖章”。