Laboratório Associado para a Química Verde, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
Int J Mol Sci. 2022 Mar 18;23(6):3292. doi: 10.3390/ijms23063292.
In this manuscript, two thiouronium-based ionic liquids (ILs), namely 2-ethylthiouronium bromide [Cth][Br] and 2-(hydroxyethyl)thiouronium bromide [COHth][Br], were tested at different concentrations (1 and 10 wt%) for their ability to affect CO (sI) and tetrahydrofuran (THF) (sII) hydrate formation and growth. Two different methods were selected to perform a thermodynamic and kinetic screening of the CO hydrates using a rocking cell apparatus: (i) an isochoric pressure search method to map the hydrate phase behavior and (ii) a constant ramping method to obtain the hydrate formation and dissociation onset temperatures. A THF hydrate crystal growth method was also used to determine the effectiveness of the ILs in altering the growth of type sII hydrates at atmospheric pressure. Hydrate-liquid-vapor equilibrium measurements revealed that both ILs act as thermodynamic inhibitors at 10 wt% and suppress the CO hydrate equilibria ~1.2 °C. The constant ramping methodology provides interesting results and reveals that [COHth][Br] suppresses the nucleation onset temperature and delays the decomposition onset temperatures of CO hydrates at 1 wt%, whereas suppression by [Cth][Br] was not statistically significant. Normalized pressure plots indicate that the presence of the ILs slowed down the growth as well as the decomposition rates of CO hydrates due to the lower quantity of hydrate formed in the presence of 1 wt% ILs. The ILs were also found to be effective in inhibiting the growth of type sII THF hydrates without affecting their morphology. Therefore, the studied thiouronium ILs can be used as potential dual-function hydrate inhibitors. This work also emphasizes the importance of the methods and conditions used to screen an additive for altering hydrate formation and growth.
在本手稿中,我们测试了两种基于硫代铵的离子液体(ILs),即 2-乙基硫代铵溴化物 [Cth][Br] 和 2-(羟乙基)硫代铵溴化物 [COHth][Br],以评估它们在不同浓度(1 和 10wt%)下影响 CO(sI)和四氢呋喃(THF)(sII)水合物形成和生长的能力。我们选择了两种不同的方法使用摇滚细胞装置对 CO 水合物进行热力学和动力学筛选:(i)等压搜索法绘制水合物相行为图,(ii)恒斜率法获得水合物形成和分解起始温度。还使用 THF 水合物晶体生长方法来确定 ILs 在改变常压下 sII 水合物生长的有效性。水合物-液体-蒸气平衡测量结果表明,两种 IL 在 10wt%时均作为热力学抑制剂,使 CO 水合物平衡降低约 1.2°C。恒斜率方法提供了有趣的结果,表明[COHth][Br]在 1wt%时抑制 CO 水合物的成核起始温度并延迟其分解起始温度,而[Cth][Br]的抑制作用则不具有统计学意义。归一化压力图表明,由于在 1wt% IL 存在下形成的水合物量较少,IL 的存在减缓了 CO 水合物的生长和分解速率。IL 还被发现有效抑制了 sII 型 THF 水合物的生长,而不影响其形态。因此,所研究的硫代铵 IL 可以用作潜在的双重功能水合物抑制剂。这项工作还强调了筛选改变水合物形成和生长的添加剂时所使用的方法和条件的重要性。