六铝酸盐氧载体甲烷化学链燃烧过程研究

Carbon dioxide (CO2) is a major greenhouse gas, which mainly comes from the combustion of fossil fuels. In recent years, worldwide efforts have been contributed to CO2 capture. Chemical looping combustion (CLC) is a novel combustion technology that offers the inherent feature of isolating CO2, low NOx emissions compared with conventional combustion technology. One of the key issues is the sintering of the oxygen carrier (OC) occurring during the redox cycles at high temperature (800-1000 oC) and its deleterious effect on the capacity of the oxygen to transport and release oxygen. In this proposal, we will use hexaaluminates, a class of excellent high-temperature materials as OC for CLC of methane. The effect of lattice oxygen which can be tuned by varying the component and content of large cations and transition metals on the selectivity to CO2 as well as the stability of multi-redox cycles will be investigated. In addition, various types of physical chemistry techniques will be employed to investigate the structure, chemical state of transition metals and mobility of lattice oxygen in order to establish the relationship between these properties and the selectivity to CO2 as well as the stability of multi-redox cycles. Combined with a kinetic study, the mechanism of CLC of methane over hexaaluminates will be proposed.

化石燃料的燃烧是人类排放CO2的主要来源。CO2是引起“温室效应”的元凶，减少二氧化碳的排放是当前全世界所面临的艰巨任务。化学链燃烧是一种新型的燃烧技术，可以实现CO2的自动分离和避免NOx污染物的产生，已成为理论上和技术上关注的焦点。氧载体是化学链燃烧技术的关键所在，目前为止，氧载体的高温烧结仍然是阻碍深入研究化学链燃烧过程的因素之一。本申请以耐高温性能优异的六铝酸盐为CH4化学链燃烧氧载体，通过大阳离子和过渡金属种类、取代量调变六铝酸盐氧载体晶格氧的移动性，并考察其对六铝酸盐氧载体CO2选择性、氧化还原循环稳定性的影响。借助多种物理化学表征手段研究六铝酸盐氧载体晶相结构、过渡金属的化学状态、晶格氧的移动性，并与六铝酸盐氧载体CO2选择性、氧化还原循环稳定性进行关联。利用化学动力学研究六铝酸盐氧载体CH4化学链燃烧过程，力图阐明六铝酸盐氧载体CH4化学链燃烧反应机理。

化学链燃烧是一种新型的燃烧技术，可以实现CO2的自动分离和避免NOx污染物的产生，已成为理论上和技术上关注的焦点。氧载体是化学链燃烧技术的关键所在，目前为止，氧载体的高温烧结仍然是阻碍深入研究化学链燃烧过程的因素之一。该申请将金属离子引入具有高温稳定性、晶格可镶嵌性以及晶格氧移动性特征的六铝酸盐晶格中和在α-Al2O3载体中添加La以提高活性物种稳定性，重点研究了其甲烷CLC反应活性和氧化还原稳定性、六铝酸盐结构中与金属离子配位的晶格氧的晶位和移动性以及La的添加对Fe2O3/α-Al2O3氧载体反应前后结构的影响。采用各种表征技术建立了氧载体的构效关系，为高性能化学链燃烧氧载体提供研制方向和理论基础。