复合碱金属盐修饰MgO基CO2吸附剂的设计制备及吸附机理研究

The MgO-based sorbents promoted with mixed alkali metal salts have the ability to capture CO2 at 300-400 °C, making them potential candidates for pre-combustion CO2 capture. However, research and development on such sorbents is limited by the lack of understanding of key factors affecting the sorbent performance and the mechanism of CO2 sorption on the sorbent. The proposed project is going to investigate two key factors: composition of mixed alkali metal nitrate and carbonate, and morphological structure of sorbent. The former is optimized by correlation analysis between the composition of alkali metal nitrate and the solubility of CO2, MgO and alkali metal carbonate in molten alkali metal nitrate, while the latter is optimized according to the optimal grain size of sorbent derived from the critical product layer thickness in the reaction of CO2 with MgO. Next, flower-like MgO promoted with mixed alkali metal salts will be prepared based on the above results, and the structural properties of sorbent will be tuned in order to achieve high CO2 uptake and good stability during cyclic operation. Finally, the sorption mechanism of CO2 on the alkali metal salt-promoted MgO-based sorbent will be explored by studying the evolution of alkali metal nitrate and carbonate during the CO2 capture, based on which the sorption kinetic model and the fixed-bed sorption model will be developed and used for optimizing the operating conditions. The above research is of important theoretical and practical significance to reduction of CO2 emission in coal-fired power plants.

复合碱金属盐修饰MgO吸附剂因其在300-400ºC范围具有一定的CO2吸附能力、适合于燃烧前CO2捕集系统而受到关注。然而，由于对影响MgO吸附剂性能的关键因素认识不足且吸附机理不清，人们在研制此类吸附剂时往往带有一定的盲目性。本项目拟从复合碱金属盐组成和吸附剂形貌结构这两个影响吸附剂性能的关键因素入手，通过研究CO2、MgO和碱金属碳酸盐在熔融碱金属硝酸盐中的溶解度并与硝酸盐组成进行关联，优化复合碱金属硝酸盐和碳酸盐的组成；通过研究临界产物层厚度，确定吸附剂的最佳微粒尺寸。在此基础上，设计制备具有花形结构的复合碱金属盐修饰MgO吸附剂，调控其结构性质，实现高CO2吸附量和高稳定性。探究碱金属硝酸盐和碳酸盐在CO2吸附过程中的演化规律，揭示吸附剂与CO2的作用机理，进而构建吸附动力学模型和吸附床数学模型，优化吸附操作条件。本研究对于燃煤电厂CO2减排具有重要的理论和现实意义。

本项目以化石燃料燃烧前CO2捕集为研究背景，旨在设计制备高性能的复合碱金属盐修饰MgO基CO2吸附剂并探究其吸附机理，研究其中涉及的关键科学问题和技术问题，目的是揭示这些关键科学问题的本质，解决其中的关键技术问题，为MgO基CO2吸附剂的工业应用提供理论和技术支撑。项目的主要研究内容包括：制备复合碱金属硝酸盐和碳酸盐（alkali metal salt, AMS）修饰的MgO基CO2吸附剂，优化AMS的组成，揭示吸附剂的结构与性能关系；制备NaNO3修饰的MgO基吸附剂，考察CdO或Li3PO4掺杂的影响，探究CO2吸附机理；将MgO基吸附剂应用于水气变化反应，研究CO2吸附强化水气变化反应过程；探索捕集CO2的转化利用。通过上述研究，我们掌握了MgO基吸附剂形貌结构的调控方法，优化了复合碱金属盐的组成，获得了性能优异的MgO基CO2吸附剂；掌握了碱金属硝酸盐和碳酸盐在CO2吸附过程中的演化规律，揭示了CO2与MgO基吸附剂的作用机制。截止目前，本项目一共发表了SCI收录的论文12篇，包括ACS Applied Materials & Interfaces (1篇)、Journal of Materials Chemistry A (1篇)、Chemical Engineering Journal (3篇)、AIChE Journal (1篇)、Chemical Engineering Science (1篇)、Journal of Catalysis (1篇)、Applied Catalysis A: General (1篇)、Catalysis Science & Technology (1篇)、Sustainable Energy & Fuels (1篇)、Catalysis Communications (1篇)；申请了国家发明专利4项，均已公开；培养了博士生2名，硕士生3名。