Landuyt Annelies, Kochetygov Ilia, McMonagle Charles J, Kumar Priyank V, Yuwono Jodie A, Queen Wendy L, Abdala Paula M, Müller Christoph R
Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, 8092 Zürich, Switzerland.
Paul Scherrer Institut, PSI Center for Energy and Environmental Sciences, Villigen, PSI CH-5232, Switzerland.
JACS Au. 2024 Nov 16;4(12):4809-4820. doi: 10.1021/jacsau.4c00782. eCollection 2024 Dec 23.
There is an urgent need for inexpensive, functional materials that can capture and release CO under industrial conditions. In this context, MgO is a highly promising, earth-abundant CO sorbent. However, despite its favorable carbonation thermodynamics and potential for high gravimetric CO uptakes, MgO-based CO sorbents feature slow carbonation kinetics, limiting their CO uptake during typical industrial contact times. The addition of molten alkali metal nitrate promoters, such as NaNO, can partially mitigate the slow kinetics. Here, we investigate how the CO uptake kinetics of NaNO-promoted MgO can be increased further through the addition of finely dispersed NaCO. The incorporation of NaCO significantly increases the CO uptake rate from 1.4 to 14.6 mmol MgCO (mol MgO) s. Using synchrotron X-ray powder diffraction (XRD), we track the formation of MgCO and elucidate the mechanism through which NaCO promotes the CO uptake of MgO. Our findings demonstrate that NaCO rapidly converts within seconds into NaMg(CO) during carbonation, acting subsequently as nucleation seeds for MgCO formation, in turn significantly enhancing CO uptake kinetics. Further, the presence of NaMg(CO) considerably enhances the mobility of ions in the sorbent, leading to sintering of MgCO. Importantly, NaMg(CO) promotes MgCO formation even in the presence of molten RbNO, a salt with a limited ability to dissolve [Mg···CO ] ion pairs, indicating that NaMg(CO) lowers the critical ion pair concentration required for MgCO nucleation. Additionally, the partial dissolution of NaCO in NaNO may increase the concentration of carbonate ions in the melt, further accelerating carbonation kinetics in MgO-(NaCO/NaNO).
迫切需要能够在工业条件下捕获和释放二氧化碳的廉价功能性材料。在此背景下，氧化镁是一种极具前景、储量丰富的二氧化碳吸附剂。然而，尽管其碳酸化热力学性质良好且具有较高的二氧化碳重量吸收潜力，但基于氧化镁的二氧化碳吸附剂的碳酸化动力学缓慢，限制了它们在典型工业接触时间内的二氧化碳吸收量。添加熔融碱金属硝酸盐促进剂，如硝酸钠，可以部分缓解缓慢的动力学问题。在此，我们研究如何通过添加精细分散的碳酸钠进一步提高硝酸钠促进的氧化镁的二氧化碳吸收动力学。碳酸钠的加入显著提高了二氧化碳吸收速率，从1.4 mmol MgCO (mol MgO) s提高到14.6 mmol MgCO (mol MgO) s。使用同步加速器X射线粉末衍射(XRD)，我们追踪碳酸镁的形成，并阐明碳酸钠促进氧化镁吸收二氧化碳的机制。我们的研究结果表明，碳酸钠在碳酸化过程中在几秒钟内迅速转化为NaMg(CO)，随后作为碳酸镁形成的成核种子，进而显著提高二氧化碳吸收动力学。此外，NaMg(CO)的存在大大提高了吸附剂中离子的迁移率，导致碳酸镁烧结。重要的是，即使在熔融硝酸铷存在的情况下，NaMg(CO)也能促进碳酸镁的形成，硝酸铷是一种溶解[Mg···CO ]离子对能力有限的盐，这表明NaMg(CO)降低了碳酸镁成核所需的临界离子对浓度。此外，碳酸钠在硝酸钠中的部分溶解可能会增加熔体中碳酸根离子的浓度，进一步加速氧化镁-(碳酸钠/硝酸钠)体系中的碳酸化动力学。
