Maynor Karey, Bhati Awan, Hamalian Mark, Ferraria Ana Maria, Ribeiro Ana Paula da Costa, Moita Ana S, Bahadur Vaibhav
Walker Department of Mechanical Engineering, The University of Texas at Austin, 204 E. Dean Keeton Street, Austin, Texas 78712, United States.
Institute for Bioengineering and Biosciences and Departamento de Engenharia Química, Instituto Superior Técnico, and Associate Laboratory i4HB-Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisbon 1049-001, Portugal.
Langmuir. 2024 Oct 15;40(41):21758-21766. doi: 10.1021/acs.langmuir.4c02882. Epub 2024 Oct 2.
Hydrates are ice-like crystalline structures of hydrogen-bonded water molecules that trap a guest molecule. Hydrates have several applications, including carbon sequestration, gas separation, desalination, etc. A classical major challenge associated with artificial hydrate formation is the very long induction time to nucleate hydrates. This has spurred the development of multiple chemical, mechanical, and electrical strategies to promote nucleation. Presently, we discover that magnesium can significantly promote the nucleation of tetrahydrofuran (THF) hydrates. While magnesium has been recently shown (by our group) to promote the formation of carbon dioxide hydrates (gas-liquid system), this study discovers that the benefits of magnesium extend to liquid-liquid hydrate systems as well. Experiments show that magnesium reduces the induction time for THF hydrate nucleation with deionized (DI) water and saltwater by six and eight times, respectively. Magnesium-induced nucleation rate enhancements for hydrate formation with DI water and saltwater were 12 and 99 times, respectively. Importantly, we demonstrate near-instantaneous nucleation when magnesium is introduced after the hydrate-forming system reaches suitable thermodynamic conditions. We conduct statistically significant measurements of nucleation and XPS analysis to identify the underlying mechanisms responsible for nucleation. We discuss multiple phenomena at play, including chemical and mechanistic promotion pathways. The formation of hydrogen bubbles and the presence of magnesium ions in solution are seen as important to magnesium-based nucleation promotion. Importantly, very low amounts of Mg are consumed in this process unlike in traditional chemical promotion techniques. Overall, our discovery can enable on-demand nucleation of liquid-liquid hydrate systems, which is critical to the development of several applications.
水合物是由氢键连接的水分子形成的类似冰的晶体结构，其中捕获了客体分子。水合物有多种应用，包括碳封存、气体分离、海水淡化等。与人工水合物形成相关的一个经典重大挑战是水合物成核的诱导时间非常长。这促使人们开发了多种化学、机械和电气策略来促进成核。目前，我们发现镁可以显著促进四氢呋喃（THF）水合物的成核。虽然最近（我们小组）已表明镁能促进二氧化碳水合物（气液体系）的形成，但本研究发现镁的益处也延伸到液-液水合物体系。实验表明，镁分别将用去离子水（DI）和盐水形成THF水合物的诱导时间缩短了6倍和8倍。用DI水和盐水形成水合物时，镁诱导的成核速率增强分别为12倍和99倍。重要的是，我们证明了当在水合物形成系统达到合适的热力学条件后引入镁时，几乎能瞬间成核。我们对成核进行了具有统计学意义的测量和XPS分析，以确定负责成核的潜在机制。我们讨论了多种起作用的现象，包括化学和机械促进途径。氢气泡的形成和溶液中镁离子的存在被认为对基于镁的成核促进很重要。重要的是，与传统化学促进技术不同，在此过程中消耗的镁量非常少。总体而言，我们的发现能够实现液-液水合物体系的按需成核，这对多种应用的开发至关重要。
