College of Environmental Science and Engineering, Beijing Forestry University, 35 Qinghua East Road, Haidian District, Beijing 100083, P. R. China.
Chemistry Department, Heterogeneous Catalysis Lab, University of Cyprus, 1 University Ave., University Campus 2109 Nicosia, Cyprus.
Environ Sci Technol. 2021 Apr 20;55(8):4513-4521. doi: 10.1021/acs.est.0c08731. Epub 2021 Mar 22.
Optimization of MgO adsorbents is predominantly focused on the regulation of appropriate adsorption sites for CO associated with Mg-O sites of low coordination. Here, for the first time, we conducted transient kinetic experiments to identify and characterize changes of the CO molecular path in MgO-based CO adsorbents upon the addition of molten salt modifiers. Among the optimized samples, addition of 10 mol % NaNO on the surface of MgO exhibited the highest CO uptake (15.7 mmol g) at 350 °C compared to less than 0.1 mmol g for the unpromoted MgO. Kinetic modeling showed that the interaction of molten salt-promoted MgO with CO at 300 °C involves three different processes, namely, fast surface adsorption associated with surface-active basic sites, chemical reaction associated with MgCO formation, and a slow diffusion step being the rate-limiting step of the carbonation process. Furthermore, transient kinetic studies coupled with mass spectrometry under low CO partial pressure agreed well with the kinetic simulation results based on TGA measurements, demonstrating an in-depth understanding of the CO-capturing performance gained and its considerable significance for future practical designs of precombustion CO capture.
氧化镁吸附剂的优化主要集中在调节与低配位 Mg-O 位相关的 CO 的适当吸附位。在这里，我们首次进行了瞬态动力学实验，以在添加熔融盐改性剂时识别和表征基于氧化镁的 CO 吸附剂中 CO 分子路径的变化。在优化的样品中，与未促进的氧化镁相比，氧化镁表面添加 10 mol % 的 NaNO 在 350°C 时表现出最高的 CO 吸收量（15.7 mmol g），不到 0.1 mmol g。动力学模型表明，在 300°C 下，熔融盐促进的氧化镁与 CO 的相互作用涉及三个不同的过程，即与表面活性碱性位相关的快速表面吸附、与 MgCO 形成相关的化学反应，以及作为碳化过程的速率限制步骤的缓慢扩散步骤。此外，在低 CO 分压下进行的瞬态动力学研究与质谱相结合，与基于 TGA 测量的动力学模拟结果非常吻合，这证明了对 CO 捕获性能的深入了解及其对未来预燃烧 CO 捕获的实际设计具有重要意义。
