Yongwon Seo

Ulsan National Institute of Science and Technology | UNIST · School of Urban and Environmental Engineering

This research explores the innovative method of enhancing carbon capture by substituting methane hydrate with CO2 in ocean sediments, a promising strategy for mitigating greenhouse gas emissions. Methane hydrates, ice-like compounds where methane is trapped within a water molecule cage, are abundant in marine sediments and offer a potential target...

쇄빙선 아라온호를 이용한 북극해 지역의 가스 하이드레이트 탐사는 2016년부터 시작되었다. 중력 코어링을 통해 2018년과 2019년에는 동시베리아 척치해에서, 2022년도에는 캐나다 보퍼트해에서 가스 하이드레이트 샘플 채취에 성공하였다. 가스 하이드레이트 샘플은 액체질소 보관통 (dry shipper)에 저장하여 한국으로 이동하였으며, 이 가스 하이드레이트 샘플의 물리화학적 및 열역학적 특성을 파악하기 위하여 기체 크로마토그래피를 이용한 조성 분석, 13C NMR, PXRD (powder X-ray diffraction), 라만 분광기를 이용한 구조 분석, 그리고, 퇴적층에서의 염 농도 분석을 수행하였다. 2018년과...

Fluorinated gases (F-gases), such as CHF3 and C2F6, which are used in the semiconductor industry and have considerable global warming potential, can be recovered after use through a gas hydrate-based separation method to prevent their release into the atmosphere. In this study, the guest distributions and dissociation enthalpy (ΔHd) of F-gas (CHF3...

Tetra-n-butyl ammonium chloride (TBAC) is a semi-clathrate former that can be used for clathrate-based gas capture and storage since TBAC semi-clathrate has vacant small cages available for entrapping gas molecules under mild conditions. In this study, the phase equilibria and structural information of TBAC + Xe + water systems were experimentally...

In this study, three dipeptides (Gly-Gly, Ala-Ala, and Ala-Gly) were appraised as environmentally benign hydrate inhibitors for CH4 hydrate using both experimental and computational methods. Their kinetic inhibition performance was experimentally evaluated using a stirred high-pressure autoclave and a non-stirred high-pressure micro-differential sc...

In this study, the guest exchange behaviors in the hydrate-bearing sediment of a one-dimensional reactor specially designed for depressurization-assisted replacement were experimentally investigated for CH4 production and CO2 storage. The longitudinal distributions of vapor compositions, replacement efficiency, and hydrate weight fractions, as well...

The importance of carbon capture and storage (CCS) has recently been emphasized owing to the ever-increasing global warming. Direct CO2 sequestration in marine sediments is an attractive option for CO2 storage, and some amount of injected CO2 can be stored in the form of solid gas hydrates. In this study, the effects of NaCl on the hydrate phase eq...

Freshwater can be obtained through gas hydrate formation from saline water, which is called hydrate-based desalination (HBD). In this study, the thermodynamic and kinetic features of propane, R134a, R22, and R152a hydrates in the presence of NaCl were examined to determine the energy-efficient gaseous hydrate former. Structure I hydrate formers (R2...

CO2 hydrate formation in the CO2 transmission pipelines for ocean or geological sequestration can result in pipeline blockage and rupture. Herein, monomeric substances (urea (U), acetamide (A), and glycine (G)) that are easily decomposable were evaluated as kinetic hydrate inhibitors and potential synergists for CO2 hydrate using experimental and c...

In this study, an effective hybrid inhibition of gas hydrates and corrosion was investigated to overcome compatibility problems between inhibitors and reduce the cost of production and transportation operations in the oil and gas industry. The newly synthesized waterborne polyurethanes (WPUs) were appraised as efficient dual-purpose gas hydrate and...

Fused aromatic networks (FANs) are attracting considerable interest in the scientific community because of their intriguing electronic properties and superior physiochemical stability due to their fully fused aromatic systems. Here, a three-dimensional (3D) cage-like organic network (3D-CON) and a vertical two-dimensional (2D) layered ladder struct...

Both natural gas production and CO2 sequestration can be simultaneously achieved in natural gas hydrates (NGHs) by using a guest swapping technique. In this study, the effects of replacement pressure (10.0–18.5 MPa) and temperature (274.2–277.2 K) conditions on the guest exchange behaviors of CH4 − CO2 + N2 replacement were investigated, focusing o...

In this study, a new sI-sII dual hydrate former [chlorodifluoromethane (CHClF2); an important greenhouse gas with a global warming potential of 1810], which forms sI hydrate by itself and forms sII hydrate in the presence of external help guests such as CH4 and N2, was introduced and closely investigated for its potential significance in gas hydrat...

In this study, the thermodynamic and structural characteristics of natural gas hydrates (NGHs) retrieved from gas hydrate mounds (ARAON Mound 03 (AM03) and ARAON Mound 06 (AM06)) in the Chukchi Sea in the Arctic region were investigated. The gas compositions, crystalline structure, and cage occupancy of the NGHs at AM03 and AM06 were experimentally...

In this study, urea (U), acetamide (A), and glycine (G), which are easily decomposable, were suggested as kinetic hydrate inhibitors (KHIs) and potential synergists for CH4 hydrate. The inhibition performance of these substances was evaluated by measuring the onset temperature of CH4 hydrate via both a stirred high-pressure autoclave and a non-stir...

In this study, the dissociation behavior and the time-dependent guest distributions of methane (CH4) hydrate after the injection of gaseous N2 were closely investigated using gas chromatography, in situ Raman spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy for two different N2 gas injecting pressures (4.0 and 8.0 MPa) at three diffe...

The complex phase behaviors and structural coexistence of natural gas hydrates (NGHs) that contain large-molecule guest substances (LMGSs) were examined for their significance in the exploration and exploitation of NGHs as well as natural gas storage and transportation. Methylcyclopentane (MCP) and 2,2-dimethylbutane [neohexane (NH)] were chosen as...

The feasibility of hydrate-based sulfur hexafluoride (SF6) separation was investigated by primarily focusing on the thermodynamic, kinetic, and structural characteristics of SF6 + N2 hydrates, the separation efficiency, and the equilibrium recovery ratio. Three-phase (hydrate (H)–water (LW)–vapor (V)) equilibria of SF6 + N2 hydrates were measured t...

In this study, three kinds of driving forces for the dissociation of CH4 hydrates were experimentally investigated to determine which was optimal for a consistent control of the depressurization process. A specially designed one-dimensional (1-D) reactor was used to examine the production behavior of CH4 from the hydrate-bearing sediment using depr...

Hydrate-based desalination (HBD), a type of freezing-based desalination, can concentrate salts of saline water and produce fresh water via hydrate crystal formation. In this study, the thermodynamic stability, crystallographic information, and kinetic growth behavior of HFC-152a hydrate were investigated to estimate the desalination efficiency of H...

This study examined the complex phase behavior and structures of natural gas hydrates containing large-molecule guest substances (LMGSs). Methylcyclopentane (MCP) and 2,2-dimethylbutane (neohexane, NH) were selected as LMGSs for CH4 (90%) + C3H8 (10%) hydrates. To verify the exact role of LMGSs, the four-phase (hydrate (H) – liquid water (LW) – liq...

In this study, the kinetics of guest exchange in sII (CH4 (90%) + C3H8 (10%)) hydrate – flue gas (CO2 (20%) + N2 (80%)) replacement was investigated to elucidate the replacement mechanism and guest exchange characteristics for hydrocarbon recovery and CO2 sequestration. The Rietveld refinement of Powder X-ray diffraction (PXRD) patterns of the repl...

This study analyzed the potential effects of gas hydrate (GH) exploitation on the geomechanical properties of hydrate-bearing sediment (HBS) by examining the combined effects of depressurization and CO2 injection using triaxial compression tests. The stress-strain behavior of the initial CH4 HBS showed strong hardening-softening characteristics and...

This study investigated the influence of feed gas composition on structural transformation and guest exchange behaviors in the replacement of sH (CH4 + methylcyclopentane) hydrate with CO2 + N2 for energy recovery and CO2 sequestration. CO2 + N2 mixtures with three different CO2 concentrations (20, 40, and 60%) were used as replacement gases, and t...

In this study, the thermodynamic inhibition effects of choline chloride (ChCl, a hydrogen bond acceptor), urea (a hydrogen bond donor), and their mixture (deep eutectic solvent, DES) on CH4 hydrates were investigated with both experimental and computational approaches. The synthesis of DES from the mixture of ChCl and urea was confirmed by measurin...

Sulfur hexafluoride (SF6), the most potent greenhouse gas, should be separated from gas mixtures for recycling and for mitigation of global warming. In this study, the formation and dissociation behaviors of SF6 hydrates in the presence of a surfactant (sodium dodecyl sulfate, SDS) and an antifoaming agent (antifoam A concentrate, AAC) were investi...

This study investigated structural transformation, guest distributions, and the extent of replacement for CH4+C3H8 – flue gas replacement occurring in sII hydrates via gas chromatography, NMR spectroscopy, and powder X-ray diffraction (PXRD). Simulated flue gas (CO2 (20%)+N2 (80%)) was injected into an sII CH4 (90%)+C3H8 (10%) hydrate for guest exc...

CH4–CO2 replacement in naturally occurring gas hydrates has been considered a promising method for both energy recovery and CO2 sequestration. In this study, the time-dependent guest exchange behaviors and guest distributions during CH4–CO2 replacement were closely examined at two different CO2 injecting pressures (2.2 and 3.5 MPa) using nuclear ma...

This study examined the synergistic inhibition effect of glycine (an amino acid) and [BMIM][BF4] (an ionic liquid) on the thermodynamic phase equilibria and growth behaviors of CH4 hydrates. Hydrate phase equilibria indicated that there was no thermodynamic synergism of inhibitor mixtures on CH4 hydrates. Powder X-ray diffraction (PXRD) patterns de...

In this study, the kinetic inhibition effects of amino acids and ionic liquids and the potential synergism of their mixtures on CH4 hydrates were investigated by adopting three different approaches. The sigma (σ) profiles of inhibitor molecules obtained from the Conductor-Like Screening Model for Real Solvents (COSMO-RS) software were used to estim...

Amino acids (glycine and alanine) and ionic liquids ([BMIM][BF4] and [BMIM][I]) were examined for their inhibition effects on CH4 hydrates with experimental and computational approaches. Both amino acids and ionic liquids functioned well as thermodynamic hydrate inhibitors, by shifting equilibrium curves of CH4 hydrates toward harsh conditions. How...

Upgrading CO 2 -rich natural gas or biogas through CO 2 capture is essential to reduce greenhouse gas emissions and to increase its energy density. In this study, clathrate-based CO 2 capture from CO 2 -rich natural gas or biogas was investigated with a primary focus on kinetic CO 2 selectivity. The time-dependent CO 2 selectivity during clathrate...

The source-receptor relationship of volatile organic compounds (VOCs) is an important environmental concern, particularly in large industrial cities; however, only a few studies have identified VOC sources using high spatial resolution data. In this study, 28 VOCs were monitored in Ulsan, the biggest multi-industrial city in Korea. Passive air samp...

In this study, HFC-125a was selected as a hydrate-forming guest for gas hydrate-based desalination. The thermodynamic and kinetic effects of NaCl on HFC-125a hydrates were investigated with a primary focus on phase equilibria, gas uptake, dissociation enthalpy, and dissociation behavior. The equilibrium curve of HFC-125a hydrate shifted to higher p...

In this study, stability conditions and characterization of guest gas (CH4 and N2) + CP hydrates were investigated with a primary focus on phase equilibria and microscopic analyses. Four-phase (H-LW-LCP-V) equilibria of the CH4 + CP and N2 + CP hydrates measured at the pressure range of 0 - 11 MPa demonstrated that CP could significantly reduce hyd...

C2F6 (hexafluoroethane, R116) is a fluorinated gas (F-gas) widely used in semiconductor industries, which also has a high global warming potential and a long atmospheric lifetime. In this study, the thermodynamic and structural characteristics of the C2F6 + N2 gas hydrates were investigated for gas hydrate-based C2F6 separation from emission source...

In this study, the feasibility of the hydrate-based greenhouse gas (CHF3) separation was investigated with a primary focus on thermodynamic, structural, and cage-filling characteristics of CHF3 + N2 hydrates. The three-phase (hydrate (H)–liquid water (LW)–vapor (V)) equilibria of the CHF3 (10, 20, 40, 60, and 80%) + N2 + water systems provided the...

The phase equilibria, structural transition, gas uptake, and composition of CO2 + N2 + methylcyclopentane (MCP) hydrates were investigated for their potential applications in CO2 capture and sequestration. Thermodynamic stability conditions indicated that flue gas could form sH hydrates in the presence of MCP at a reduced pressure and an elevated t...

Tetrahydrofuran (THF) as a water-soluble sII clathrate former, cyclopentane (CP) as a water-insoluble sII clathrate former, and tetra n-butyl ammonium chloride (TBAC) as a water-soluble semiclathrate former were used to investigate their thermodynamic promotion effects on clathrate-based CO2 capture from simulated flue gas. The phase equilibria of...

In this study, thermodynamic stability and cage occupation behavior in the CH4 – CO2 replacement, which occurs in natural gas hydrate reservoirs by injecting flue gas, were investigated with a primary focus on phase equilibria and composition analysis. The phase equilibria of CH4/N2/CO2 mixed hydrates with various compositions were measured to dete...

Dual (thermodynamic and kinetic) inhibition effects of piperazine (PZ) and hydrazine (HZ), two representative diamines, on the formation of CH4 hydrate were investigated, primarily focusing on thermodynamic, spectroscopic, and computational analyses for their potential application in natural gas production and transportation. The phase behavior dem...

A replacement technique has been regarded as a promising strategy for both CH4 exploitation from gas hydrates and CO2 sequestration into deep-ocean reservoirs. Most research has been focused on replacement reactions that occur in sI hydrates due to their prevalence in natural gas hydrates. However, sII hydrates in nature have been also discovered i...

The CH4-flue gas replacement that occurs in structure H (sH) hydrates was investigated, with a primary focus on thermodynamic phase behavior, structure identification, heat flow monitoring, and dissociation enthalpy, for its dual function of CH4 recovery and CO2 sequestration. The significant shift in the equilibrium line of the CH4 + neohexane (2,...

In this study, gas hydrate-based fluorinated gas (F-gas) separation is proposed as a novel method to capture F-gases. This study investigates the thermodynamic, structural, and cage filling characteristics of the gas hydrates formed by two representative F-gases (CHF3 and C2F6) in order to verify the feasibility of the F-gas separation using gas hy...

Phase equilibria, structure identification, and dissociation enthalpies of HFC-134a hydrates in the presence of NaCl are investigated for potential application in desalination. To verify the influence of NaCl on the thermodynamic hydrate stability of the HFC-134a hydrate, the three-phase (hydrate (H) - liquid water (LW ) - vapor (V)) equilibria of...

The thermodynamic phase behaviors, dissociation enthalpies, and Raman spectra of N2 + tetra-n-butyl ammonium chloride (TBAC) + water systems were measured in order to investigate the enclathration of N2 in TBAC semiclathrates. The three-phase (H-Lw-V) equilibria of the N2 + TBAC (1.0, 3.3, and 5.0 mol%) semiclathrates measured using a high pressure...

The CH4 - CO2 replacement that occurs in sH hydrates is investigated with a primary focus on the enhanced CH4 recovery induced via structural transformation with a CO2 injection. In this study, neohexane (NH) is used as a liquid hydrocarbon guest in the sH hydrates. Direct thermodynamic measurements and spectroscopic identification are conducted to...

The stability of hydrate frameworks is influenced by guest molecules capable of hydrogen bonding with surrounding water molecules. Four remarkable features from the ammonium fluoride incorporation into a crystalline hydrate matrix provide important information on the thermodynamic stability, formation kinetics, structural characteristics, and molec...

The methane (CH4) - carbon dioxide (CO2) swapping phenomenon in naturally occurring gas hydrates is regarded as an attractive method of CO2 sequestration and CH4 recovery. In this study, a high pressure microdifferential scanning calorimeter (HP μ-DSC) was used to monitor and quantify the CH4 - CO2 replacement in the gas hydrate structure. The HP μ...

Investigations on the intrinsic properties of gas hydrates with multiple guests are essential to scientific and technological fields. In particular, even though evaluating and designing a hydrate phase process require isothermal phase equilibria, it is difficult to obtain extensive data with various components and compositions in a short period of...

The conversion of CH4 hydrate to CO2 hydrate with net recovery of CH4 is regarded as an attractive method of both CO2 sequestration and CH4 production. In this study, the CH4-CO2 swapping phenomenon occurring in gas hydrates and its potential application to CO2 sequestration was examined through thermodynamic equilibrium studies and a C-13 NMR spec...

In order to investigate the feasibility of semiclathrate hydrate-based pre-combustion CO2 capture, thermodynamic, kinetic, and spectroscopic studies were undertaken on the semiclathrate hydrates formed from a fuel gas mixture of H2 (60%) + CO2 (40%) in the presence of quaternary ammonium salts (QASs) such as tetra-n-butylammonium bromide (TBAB) and...

In this study, the feasibility of the hydrate-based pre-combustion capture of carbon dioxide in the presence of a thermodynamic promoter and porous silica gels was examined through stability condition measurements, gas uptake measurements, and microscopic analyses. When a fuel gas mixture of H-2 (60%) and CO2 (40%) was used for gas hydrate formatio...

The enclathration of 2-propanol (2-PrOH) as a co-guest of structure II (sII) hydrates in the presence of CH and CO was experimentally verified with a focus on macroscopic phase behaviors and microscopic analytical methods such as powder X-ray diffraction (PXRD) and NMR spectroscopy. 2-PrOH functioned as a hydrate promoter in the CH + 2-PrOH systems...

If the conversion of methane hydrate to carbon dioxide hydrate with the net recovery of methane could occur, this would be quite attractive as an innovative method of both methane production and carbon dioxide storage. In this study, the swapping phenomenon occurring in gas hydrates and its potential application to carbon dioxide sequestration was...

Guest-induced structural transformation in amine semiclathrate hydrates is a unique pattern caused by modifying the hydrophobic-hydrophilic balance, and thus, it can be applied to potential gas storage and transportation areas. The experimental results of the structural transformation of isopropylamine (IPA) semiclathrate hydrates in the presence o...

Diethylamine and n-propylamine, known as semiclathrate hydrate formers, are found to show structural transition when a help gas, CH4, was introduced. The diethylamine·8.67H2O semiclathrate hydrates (orthorhombic Pbcn) were changed to sH type (hexagonal P6/mmm) true clathrate hydrates, while the n-propylamine·6.5H2O semiclathrate hydrates (monoclini...

Gas hydrates are inclusion compounds formed when small-sized guest molecules are incorporated into the well defined cages made up of hydrogen bonded water molecules. Since large masses of natural gas hydrates exist in permafrost regions or beneath deep oceans, these naturally occurring gas hydrates in the earth containing mostly are regarded as fut...

The precise nature and unique pattern of the double tetra-n-butylammonium fluoride (TBAF) semiclathrates with a guest gas (CH(4) or CO(2)) was closely investigated through thermodynamic and spectroscopic analyses. The three-phase equilibria of semiclathrate (H), liquid water (L(W)), and vapor (V) for the ternary CH(4) + TBAF + water and CO(2) + TBA...

In this study, guest gas enclathration behavior in semiclathrates of tetra-n-butylammonium bromide (TBAB) was closely investigated through phase equilibrium measurement and spectroscopic analysis. The three-phase equilibria of semiclathrate (H), liquid water (L(W)), and vapor (V) for the ternary CH(4) + TBAB + water and CO(2) + TBAB + water mixture...

To reveal the hydrophobic hydration process of methane molecules dissolved in water, Raman spectra of dissolved methane (CH 4 ) in water were measured under various conditions. The conditions include water saturated with CH 4 gas, water–CH 4 solution with CH 4 hydrate crystals in equilibrium, and also during hydrate decomposition. The symmetric C–H...

Semiclathrate hydrate phase equilibria for N2 + TBAB (tetra-n-butylammonium bromide) + water mixtures were measured in the temperature range of (280 to 290) K and in the pressure range of (4.0 to 9.2) MPa at TBAB, w (weight fraction) = 0.05, 0.20, 0.40, and 0.60. Also, semiclathrate hydrate phase equilibria for N2 + TBAF (tetra-n-butylammonium fluo...

Structure-H hydrate has been highlighted due to its higher gas storage capacity and favorable thermal stability. Here, we introduce a new structure-H hydrate former, tert-butyl nitrite, and identify it through spectroscopic analysis. The hydrate structure and guest distribution were examined by using powder X-ray diffraction, Raman spectroscopy, an...

We measured hydrate-phase equilibria for the ternary C2H6 + NaCl (3 wt %) + water and C3H8 + NaCl (3 wt %) + water mixtures in silica gel pores of nominal 6.0, 15.0, and 30.0 nm diameters. We also measured hydrate-phase equilibria for the ternary C2H6 + NaCl + water and C3H8 + NaCl + water mixtures in nominal 30.0 nm silica gel pores at two differe...

In this study, the phase behavior and quantitative determination of hydrate composition and cage occupancy for the mixed CH(4) + C(2)H(6) + C(3)H(8) hydrates were closely investigated through the experimental measurement of three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria and (13)C NMR spectra. To examine the effect of pore siz...

This study aims to examine the thermodynamic feasibility of separating sulfur hexafluoride (SF(6)), which is widely used in various industrial fields and is one of the most potent greenhouse gases, from gas mixtures using gas hydrate formation. The key process variables of hydrate phase equilibria, pressure-composition diagram, formation kinetics,...