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Phan A, Stamatakis M, Koh CA, Striolo A. Microscopic insights on clathrate hydrate growth from non-equilibrium molecular dynamics simulations. J Colloid Interface Sci 2023; 649:185-193. [PMID: 37348338 DOI: 10.1016/j.jcis.2023.06.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Revised: 05/03/2023] [Accepted: 06/06/2023] [Indexed: 06/24/2023]
Abstract
Clathrate hydrates form and grow at interfaces. Understanding the relevant molecular processes is crucial for developing hydrate-based technologies. Many computational studies focus on hydrate growth within the aqueous phase using the 'direct coexistence method', which is limited in its ability to investigate hydrate film growth at hydrocarbon-water interfaces. To overcome this shortcoming, a new simulation setup is presented here, which allows us to study the growth of a methane hydrate nucleus in a system where oil-water, hydrate-water, and hydrate-oil interfaces are all simultaneously present, thereby mimicking experimental setups. Using this setup, hydrate growth is studied here under the influence of two additives, a polyvinylcaprolactam oligomer and sodium dodecyl sulfate, at varying concentrations. Our results confirm that hydrate films grow along the oil-water interface, in general agreement with visual experimental observations; growth, albeit slower, also occurs at the hydrate-water interface, the interface most often interrogated via simulations. The results obtained demonstrate that the additives present within curved interfaces control the solubility of methane in the aqueous phase, which correlates with hydrate growth rate. Building on our simulation insights, we suggest that by combining data for the potential of mean force profile for methane transport across the oil-water interface and for the average free energy required to perturb a flat interface, it is possible to predict the performance of additives used to control hydrate growth. These insights could be helpful to achieve optimal methane storage in hydrates, one of many applications which are attracting significant fundamental and applied interests.
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Affiliation(s)
- Anh Phan
- School of Chemistry and Chemical Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK.
| | - Michail Stamatakis
- Department of Chemical Engineering, University College London, London WC1E 7JE, UK
| | - Carolyn A Koh
- Center for Hydrate Research, Chemical & Biological Engineering Department, Colorado School of Mines, Golden, CO 80401, United States
| | - Alberto Striolo
- Department of Chemical Engineering, University College London, London WC1E 7JE, UK; School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019, United States.
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Phan A, Striolo A. Chemical Promoter Performance for CO 2 Hydrate Growth: A Molecular Perspective. ENERGY & FUELS : AN AMERICAN CHEMICAL SOCIETY JOURNAL 2023; 37:6002-6011. [PMID: 37114945 PMCID: PMC10123660 DOI: 10.1021/acs.energyfuels.3c00472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/25/2023] [Indexed: 06/19/2023]
Abstract
Carbon dioxide (CO2) hydrates, which contain a relatively large amount of captured CO2 (almost 30 wt % of CO2 with the balance being water), represent a promising CO2 sequestration option for climate change mitigation. To facilitate CO2 storage via hydrates, using chemical additives during hydrate formation might help to expedite formation/growth rates, provided the additives do not reduce the storage capacity. Implementing atomistic molecular dynamics, we study the impact of aziridine, pyrrolidine, and tetrahydrofuran (THF) on the kinetics of CO2 hydrate growth/dissociation. Our simulations are validated via reproducing experimental data for CO2 and CO2 + THF hydrates at selected operating conditions. The simulated results show that both aziridine and pyrrolidine could perform as competent thermodynamic and kinetic promoters. Furthermore, aziridine seems to exceed pyrrolidine and THF in expediting the CO2 hydrate growth rates under the same conditions. Our analysis unveils direct correlations between the kinetics of CO2 hydrate growth and a combination of the free energy barrier for desorption of CO2 from the hydrate surface and the binding free energy of chemical additives adsorbed at the growing hydrate substrate. The detailed thermodynamic analysis conducted in both hydrate and aqueous phases reveals molecular-level mechanisms by which CO2 hydrate promoters are active, which could help to enable the implementation of CO2 sequestration in hydrate-bearing reservoirs.
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Affiliation(s)
- Anh Phan
- School
of Chemistry and Chemical Engineering, Faculty of Engineering and
Physical Sciences, University of Surrey, Guildford, Surrey GU2
7XH, U.K.
| | - Alberto Striolo
- Department
of Chemical Engineering, University College
London, London WC1E 7JE, U.K.
- School
of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
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Striolo A, Huang S. Upcoming Transformations in Integrated Energy/Chemicals Sectors: Some Challenges and Several Opportunities. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:21527-21541. [PMID: 36605781 PMCID: PMC9806836 DOI: 10.1021/acs.jpcc.2c05192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 11/30/2022] [Indexed: 06/17/2023]
Abstract
The sociopolitical events over the past few years led to transformative changes in both the energy and chemical sectors. One of the most evident consequences of these events is the significant focus on sustainability. In fact, rather than an engaging discussion within elite social circles, the search for sustainability is now one of the hard requirements investors impose on companies. The concept of sustainability itself has developed since its inception, and now it encompasses environmental as well as socioeconomic aspects. The major players in the energy and chemical sectors seem to embrace these changes and the related challenges; in most cases, tangible ambitious goals have been proposed. For example, bp aims "to become a net zero company by 2050 or sooner, and to help the world get to net zero". Although tragic events such as the war in Ukraine directly affect global supply chains, leading to some reconsiderations in medium-term industrial and political strategies, trends and public demands seem determined to pursue ambitious sustainable goals, as tangible as the European Union's "Fit for 55" climate package, approved on May 12, 2022, which effectively bans internal combustion engines for new passenger cars and light commercial vehicles from 2035. These trends will likely lead to profound changes in both the chemical and energy sectors. While some predictions may miss the target, speculating about upcoming challenges and opportunities could help us prepare for the future. This is the purpose of this brief Perspective.
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Affiliation(s)
- Alberto Striolo
- School
of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
- Department
of Chemical Engineering, University College
London, London, U.K. WC1E 7JE
| | - Shanshan Huang
- Applied
Sciences, Innovation and Engineering, BP
International Ltd., Sunbury-On-Thames, U.K. TW16 7LN
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Phan A, Stamatakis M, Koh CA, Striolo A. Wetting Properties of Clathrate Hydrates in the Presence of Polycyclic Aromatic Compounds: Evidence of Ion-Specific Effects. J Phys Chem Lett 2022; 13:8200-8206. [PMID: 36006399 PMCID: PMC9442800 DOI: 10.1021/acs.jpclett.2c01846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) have attracted remarkable multidisciplinary attention due to their intriguing π-π stacking configurations, showing enormous opportunity for their use in a variety of advanced applications. To secure progress, detailed knowledge on PAHs' interfacial properties is required. Employing molecular dynamics, we probe the wetting properties of brine droplets (KCl, NaCl, and CaCl2) on sII methane-ethane hydrate surfaces immersed in various oil solvents. Our simulations show synergistic effects due to the presence of PAHs compounded by ion-specific effects. Our analysis reveals phenomenological correlations between the wetting properties and a combination of the binding free-energy difference and entropy changes upon oil solvation for PAHs at oil/brine and oil/hydrate interfaces. The detailed thermodynamic analysis conducted upon the interactions between PAHs and various interfaces identifies molecular-level mechanisms responsible for wettability alterations, which could be applicable for advancing applications in optics, microfluidics, biotechnology, medicine, as well as hydrate management.
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Affiliation(s)
- Anh Phan
- Department
of Chemical and Process Engineering, Faculty of Engineering and Physical
Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United
Kingdom
| | - Michail Stamatakis
- Department
of Chemical Engineering, University College
London, London WC1E 7JE, United Kingdom
| | - Carolyn A. Koh
- Center
for Hydrate Research, Chemical & Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Alberto Striolo
- Department
of Chemical Engineering, University College
London, London WC1E 7JE, United Kingdom
- School
of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
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Mohr S, Pétuya R, Sarria J, Purkayastha N, Bodnar S, Wylde J, Tsimpanogiannis IN. Assessing the effect of a liquid water layer on the adsorption of hydrate anti-agglomerants using molecular simulations. J Chem Phys 2022; 157:094703. [DOI: 10.1063/5.0100260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We have performed Molecular Dynamics simulations to study the adsorption of ten hydrate anti-agglomerants onto a mixed methane-propane sII hydrate surface covered by layers of liquid water of various thickness. As a general trend, we found that the more liquid water is present on the hydrate surface the less favorable the adsorption becomes, even though there are considerable differences between the individual molecules, indicating that the presence and thickness of this liquid water layer is a crucial parameter for anti-agglomerant adsorption studies. Additionally, we found that there exists an optimal thickness of the liquid water layer favoring hydrate growth due to the presence of both liquid water and hydrate-forming guest molecules. For all other cases of liquid water layer thickness, hydrate growth is slower due to the limited availability of hydrate-forming guests close to the hydrate formation front. Finally, we investigated the connection between the thickness of the liquid water layer and the degree of subcooling, and found a very good agreement between our Molecular Dynamics simulations and theoretical predictions.
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Affiliation(s)
| | | | | | | | - Scot Bodnar
- Clariant Oil Services, United States of America
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Surface morphology effects on clathrate hydrate wettability. J Colloid Interface Sci 2021; 611:421-431. [PMID: 34968961 DOI: 10.1016/j.jcis.2021.12.083] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/08/2021] [Accepted: 12/13/2021] [Indexed: 11/23/2022]
Abstract
HYPOTHESIS Clathrate hydrates preferentially form at interfaces; hence, wetting properties play an important role in their formation, growth, and agglomeration. Experimental evidence suggests that the hydrate preparation process can strongly affect contact angle measurements, leading to the different results reported in the literature. These differences hamper technological progress. We hypothesize that changes in hydrate surface morphologies are responsible for the wide variation of contact angles reported in the literature. EXPERIMENTS Experimental testing of our hypothesis is problematic due to the preparation history of hydrates on their surface properties, and the difficulties in advanced surface characterization. Thus, we employ molecular dynamics simulations, which allow us to systematically change the interfacial features and the system composition. Implementing advanced algorithms, we quantify fundamental thermodynamic properties to validate our observations. FINDINGS We achieve excellent agreement with experimental observations for both atomically smooth and rough hydrate surfaces. Our results suggest that contact line pinning forces, enhanced by surface heterogeneity, are accountable for altering water contact angles, thus explaining the differences among reported experimental data. Our analysis and molecular level insights help interpret adhesion force measurements and yield a better understanding of the agglomeration between hydrate particles, providing a microscopic tool for advancing flow assurance applications.
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