{"title":"Phase equilibria and guest gas occupancy characteristics of H2-DIOX sII hydrates based on calorimetric and Raman analysis","authors":"","doi":"10.1016/j.fluid.2024.114262","DOIUrl":null,"url":null,"abstract":"<div><div>Hydrogen (H<sub>2</sub>) as the most abundant element offers a clean energy solution for a sustainable future. Thermodynamic hydrate promoters can enhance hydrate-based H<sub>2</sub> storage under mild pressure conditions. 1,3-dioxolane (DIOX) as a low-toxicity promoter has attracted attention for its potential to improve H<sub>2</sub> hydrate kinetics. However, the phase equilibria of H<sub>2</sub>-DIOX in the presence of DIOX and its thermodynamic promotion mechanism are not fully elaborated and warrant thorough investigation. In this study, the phase equilibria of H<sub>2</sub>-DIOX hydrates were measured for DIOX concentrations (<em>C<sub>DIOX</sub></em>) ranging from 2.0 mol% to 5.56 mol%. The equilibrium temperature of H<sub>2</sub>-DIOX hydrates shifted rightward by 2.3 K at 15.0 MPa for 5.56 mol% DIOX compared to 2.0 mol% DIOX. The measured thermodynamic data were validated by fitting the H<sub>2</sub>-DIOX hydrate phase equilibira using the Clausius–Clapeyron equation. The cage occupancy of H<sub>2</sub> and DIOX in H<sub>2</sub>-DIOX sII hydrates was revealed through Raman spectroscopy and DSC thermal analysis. Two types of hydrates (DIOX and H<sub>2</sub>-DIOX) were observed for all <em>C<sub>DIOX</sub></em>. Single H<sub>2</sub> molecules were enclathrated in the 5<sup>12</sup> cages of H<sub>2</sub>-DIOX hydrates and increasing <em>C<sub>DIOX</sub></em> effectively enhanced DIOX molecules enclathration in the 5<sup>1</sup><sup>2</sup>6<sup>4</sup> cages but had limited effect on the H<sub>2</sub> molecules in the 5<sup>12</sup> cages. The findings of this study provide fundametnal thermodynamic data and cage occupancy charateristics for H<sub>2</sub>-DIOX sII hydrates below 15.0 MPa. The results provide guidance on the optimal thermodynamic promoter concentrations for future large-scale hydrate-based H<sub>2</sub> storage application.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":null,"pages":null},"PeriodicalIF":2.8000,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Fluid Phase Equilibria","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0378381224002371","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Hydrogen (H2) as the most abundant element offers a clean energy solution for a sustainable future. Thermodynamic hydrate promoters can enhance hydrate-based H2 storage under mild pressure conditions. 1,3-dioxolane (DIOX) as a low-toxicity promoter has attracted attention for its potential to improve H2 hydrate kinetics. However, the phase equilibria of H2-DIOX in the presence of DIOX and its thermodynamic promotion mechanism are not fully elaborated and warrant thorough investigation. In this study, the phase equilibria of H2-DIOX hydrates were measured for DIOX concentrations (CDIOX) ranging from 2.0 mol% to 5.56 mol%. The equilibrium temperature of H2-DIOX hydrates shifted rightward by 2.3 K at 15.0 MPa for 5.56 mol% DIOX compared to 2.0 mol% DIOX. The measured thermodynamic data were validated by fitting the H2-DIOX hydrate phase equilibira using the Clausius–Clapeyron equation. The cage occupancy of H2 and DIOX in H2-DIOX sII hydrates was revealed through Raman spectroscopy and DSC thermal analysis. Two types of hydrates (DIOX and H2-DIOX) were observed for all CDIOX. Single H2 molecules were enclathrated in the 512 cages of H2-DIOX hydrates and increasing CDIOX effectively enhanced DIOX molecules enclathration in the 51264 cages but had limited effect on the H2 molecules in the 512 cages. The findings of this study provide fundametnal thermodynamic data and cage occupancy charateristics for H2-DIOX sII hydrates below 15.0 MPa. The results provide guidance on the optimal thermodynamic promoter concentrations for future large-scale hydrate-based H2 storage application.
期刊介绍：
Fluid Phase Equilibria publishes high-quality papers dealing with experimental, theoretical, and applied research related to equilibrium and transport properties of fluids, solids, and interfaces. Subjects of interest include physical/phase and chemical equilibria; equilibrium and nonequilibrium thermophysical properties; fundamental thermodynamic relations; and stability. The systems central to the journal include pure substances and mixtures of organic and inorganic materials, including polymers, biochemicals, and surfactants with sufficient characterization of composition and purity for the results to be reproduced. Alloys are of interest only when thermodynamic studies are included, purely material studies will not be considered. In all cases, authors are expected to provide physical or chemical interpretations of the results.
Experimental research can include measurements under all conditions of temperature, pressure, and composition, including critical and supercritical. Measurements are to be associated with systems and conditions of fundamental or applied interest, and may not be only a collection of routine data, such as physical property or solubility measurements at limited pressures and temperatures close to ambient, or surfactant studies focussed strictly on micellisation or micelle structure. Papers reporting common data must be accompanied by new physical insights and/or contemporary or new theory or techniques.
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