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The shortage of fresh water is among the most serious issues in the world. A representative technology to overcome the problem is desalination, but most conventional methods (RO membrane or thermal distillation) have been focused on the treatment of relatively low salinity water, such as seawater or brackish water. To strengthen water security, in this study, we introduce a possibly economic technology for desalination of high salinity water (over-saturated concentration, in this study, a 30 wt% NaCl system) via gas hydrate formation by coupling LNG waste cold energy. First, the thermodynamic effects of NaCl on CH4 (methane), SF6 (sulfur hexafluoride), and HFC-134a hydrates were investigated. Based on the phase equilibrium of each hydrate, experimental pressures for kinetic experiments were selected under vapor pressure boundaries as follows: 4.5 MPa for CH4, 0.75 MPa for SF6, and 0.16 MPa for HFC-134a at 258.15 K (assuming the use of LNG waste cold energy). The results of the formation kinetics on the basis of gas moles consumed for hydrates showed the order CH4 > HFC-134a > SF6; however, after considering the hydration numbers and structures for each hydrate, surprisingly, the conversion rate of water to gas hydrates showed the order HFC-134a > CH4 > SF6, even though the experimental pressure condition for HFC-134a was very mild (0.16 MPa) compared to CH4 (4.5 MPa). For this interesting phenomenon, we suggest a possible mechanism through visual observations during hydrate formation. We believe these thermodynamic, kinetic, and morphological results show potential as an alternative desalination technology, especially for saturated salinity water, with lower energy consumption.

Highlights • Thermodynamic and kinetic influences of NaCl on HFC-125a hydrate were investigated. • NaCl enrichment in the unconverted solution resulted in a lower conversion. • The presence of NaCl had little effect on the ΔH of HFC-125a hydrate. • The hydrate dissociation was retarded due to the formation of NaCl⋅2H2O. 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 pressure regions at any given temperature depending on the concentration of NaCl. The presence of NaCl also reduced the gas uptake and conversion to hydrates, because of the enrichment of NaCl in the solution during gas-hydrate formation. Even though NaCl did not affect the dissociation enthalpy of the HFC-125a hydrate, the thermograms obtained using a high-pressure micro-differential scanning calorimeter (HP μ-DSC) demonstrated that HFC-125a + NaCl hydrates started to dissociate at lower temperatures due to NaCl in unconverted solutions. Rietveld refinement of powder X-ray diffraction (PXRD) patterns indicated that the HFC-125a hydrate (sII) was transformed into Ih as it dissociated. The dissociation of HFC-125a + NaCl hydrates was retarded and completely ended at higher temperatures compared to the pure HFC-125a hydrate by the sodium chloride dihydrate (NaCl⋅2H2O). Overall, these results could facilitate a better understanding of HFC-125a hydrates in the presence of NaCl; further, they might also be useful in the design and operation of hydrate-based desalination plants using HFC-125a.

Experiments of CH4 hydrate formation and decomposition were carried out in a semi-batch stirred reactor under constant temperature and pressure. In this study, we report microscopic observations such as the preferential enclathration of guest molecules by coupling an in-situ Raman spectroscopy at agitating condition in the stirred reactor. Simultaneously, the macroscopic observations (gas uptake or releasing measurements) were also reported under the same conditions. It was observed that at the beginning of hydrate growth phase, the Raman peak intensity of methane occupying the large cage (51262) and small cage (512) gradually increased after abrupt decline of dissolved methane. The encapsulation rate of large cages was faster than that of small cage throughout the hydrate formation process. In the decomposition step, the large and small cage dissociated gradually, but the dissociate rates (the ratio of Raman peak intensities of large and small cages with respect to time) were similar at the initial stage of decomposition, then large cages were dissociated more rapidly. In all experiments, we found that the Raman intensity at 3200 cm-1 is more increased along with the higher content of free water, which might will provide valuable information for further hydrogen-bonded researches including hydrate study. With the aid of in-situ Raman spectroscopy, this study successfully observed the process of hydrate formation/decomposition and further behavior of host and guest molecules under the agitated systems.

Natural gas hydrate plugging is one of the costly and challenging problems for the oil and gas industry, especially for subsea fields. One way to prevent gas hydrate formation at low cost is the use of low-dosage hydrate inhibitors (LDHI). Poly(N-isopropylmethacrylamide) (PNIPAM) with amide group have previously been shown to be an outstanding low-dosage hydrate inhibitor (LDHI). PNIPAMs are usually polymerized via radical polymerization, which can allow control over the molecular weight. We have synthesized PNIPAMs using control radical polymerization giving a fairly high degree of polymerization control. Additionally various Kinetic Hydrate Inhibitors (KHIs) were tested as CH4 hydrate inhibitors with polymeric hydrate inhibitor, PNIPAM. Furthermore, to check the synergetic effects of tetra butyl phosphonium bromide (TBPB), PNIPAM and their mixture TBPB-PNIPAM were tested as KHIs for methane gas hydrate formation. In this paper we present results on the performance of various polymeric inhibitors in KHI tests on methane gas in stirred autoclaves and on structure I hydrate formation. When PNIPAM alone was used as a single KHI, PNIPAM exhibited worst performance among the KHIs tested in this study. However the mixing of TBPB with PNIPAM further extended the induction time and reduced the CH4 hydrate growth rate. TBPB was an excellent synergist in blends with PNIPAM for kinetic hydrate inhibition of structure I forming CH4 hydrate. In summary, the mixture TBPB-PNIPAM was proven that great synergist for prevent the CH4 hydrate and good potential in achieving the industrial application of Oil & Gas production technology and therefore was a significantly meaningful discovery in the field of energy production.

Natural gas (NG), the cleanest burning fossil fuel, plays a crucial role in meeting the global energy demand, contributing to 24% and is projected to grow at a rate of about 2% until 2040. Natural gas is also considered as the bridging fuel to transition into a carbon-constrained world with reduced carbon dioxide emissions whilst catering to the huge energy demand. Efficient and effective modes of NG storage/transport are dire need in the current golden era of natural gas. A plethora of advantages offered by storing NG in the form of hydrates carve a niche for this novel technology. Termed as solidified natural gas (SNG) technology, it has remarkable potential to store multi-fold volumes of natural gas in compact hydrate crystals offering the safest and the most environmental friendly mode of NG storage. This review provides an account on the research efforts put forth in this technology. Hydrate formation and storage aspects have been examined thoroughly with a subtle account on the gas recovery. The review encompasses studies conducted using different promoters (thermodynamic, kinetic or a combination of both) in different reactor configurations, novel/innovative approaches and hybrid processes adopted to improve the kinetics of hydrate formation and to increase the gas storage capacity. Detailed sections on the ‘self-preservation’ and ‘tuning’ effect in hydrates have been included due to their significance in SNG technology. Process chain of the SNG technology, underlying challenges and measures adopted to deploy the SNG technology for large-scale NG storage applications are included in this review.

Both CO 2 and SF 6 are potent greenhouse gases responsible for global warming and associated environmental issues. Hydrate-based separation and capture of these gases from gas mixtures produced by industry have been proposed, and improving the commercial viability of these processes is crucial. Here, we report the phase equilibria and characterization of binary hydrates containing CO 2 and SF 6 . The introduction of SF 6 considerably lowered the formation pressure of CO 2 hydrates by readily occupying the structure II hydrate cages and hence altering the crystal structure. Hydrate phases with different crystalline structures were found to coexist as a result of competition in occupying different hydrate cages. The structural instability caused by the coexistence of structure I and II hydrates was observed, and this feature would be important to understand the mixed gas hydrate systems. The ability of SF 6 to significantly reduce the formation pressure of hydrates suggests that it has a potential to serve as a hydrate promoter. This feature of SF 6 combined with its non-toxic and non-flammable properties would be efficient for practical applications such as CO 2 sequestration using hydrates.

The inclusion of tert -butyl alcohol (tBA) as a co-guest of clathrate hydrates in the presence of CH 4 , CO 2 , and N 2 was investigated for its potential role in gas storage and CO 2 sequestration. The 13 C NMR, Raman spectroscopy, and powder X-ray diffraction revealed that the guest gas (CH 4 , CO 2 , and N 2 ) + tBA + water systems form sII hydrates. The enclathration of tBA molecules in the sII large (5 12 6 4 ) cages resulted in significant thermodynamic stabilization of the CH 4 + tBA and N 2 + tBA hydrates. However, the hydrate phase equilibrium curves of the CO 2 + tBA hydrates were shifted to inhibited regions despite the participation of tBA molecules as a co-guest in the sII hydrate lattices. tBA was found to function as a thermodynamic promoter for both CH 4 and N 2 hydrates, whereas it functioned as a thermodynamic inhibitor for CO 2 hydrate. The overall experimental results provide a better understanding of the thermodynamic behaviors, structural transitions, and guest distributions of the guest gas (CH 4 , CO 2 , and N 2 ) + tBA hydrates for the potential use of tBA in gas storage and CO 2 sequestration.

In this study, the influences of large molecular alcohols (LMAs) including pinacolyl alcohol (PCA) and tert-amyl alcohol (tAA) on thermodynamic phase behaviors and structural characteristics of CH 4 and CO 2 hydrates were investigated for their potential use in gas storage and CO 2 sequestration. The experimentally measured hydrate phase equilibria demonstrated that CH 4 hydrates were stabilized in the presence of PCA and tAA. 13 C NMR and Raman spectroscopy confirmed sH hydrate formation from both CH 4 + PCA + water and CH 4 + tAA + water systems, resulting from the enclathration of LMAs in the large 5 12 6 8 cages. The sH hydrate formation of the CH 4 + PCA + water system was also confirmed by an endothermic dissociation thermogram from a differential scanning calorimeter (DSC). In contrast with CH 4 hydrates, the addition of both PCA and tAA to CO 2 hydrates resulted in thermodynamic inhibition. Through Raman and powder X-ray diffraction (PXRD) analyses, both CO 2 + PCA and CO 2 + tAA hydrates were characterized as sI hydrates, indicating that LMAs simply inhibit the formation of CO 2 hydrates without being captured in the hydrate lattices. Therefore, PCA and tAA are expected to function as thermodynamic promoters which reduce the hydrate forming pressure in natural gas storage applications, while they can serve as thermodynamic inhibitors which prevent CO 2 hydrate formation in pipelines for CO 2 transportation to sequestration sites.

In order to evaluate hydrate-based desalination (HBD), experiments with seawater samples were carried out at various conditions (i.e. hydraulic pressure, washing step, and hydrate-forming gas). Before and after the hydrate process, cations (Na+, K+, Mg2 +, Ca2 +, and B3 +) and anions (Cl− and SO42 −) were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ion chromatography (IC). In a single stage of CO2 hydrate process without any pretreatment, 71%–94% of each cation was removed in the following order: K+ > Na+ ≈ Mg2 + ≈ Ca2 + > B3 + and 73%–83% of each anion was removed. When the brines on the surface of hydrate pellets were removed, the ion removal efficiency increased above 4%. It was also found that the desalting efficiency depended on the hydrate-forming gas (CO2 > CH4) and the hydraulic pressure (6–10 MPa) to produce hydrate pellets. In this study, the removal efficiency of cations and anions in a real seawater sample using HBD processes were reported for the first time.

The characteristics of methane–propane hydrate crystal growth on the surface of gas bubble in pure water were investigated using optical microscope and compared with those in aqueous solutions of sodium dodecyl sulfate (SDS) or poly-N-vinylcaprolactam (PVCap). Most of morphology works in literature mainly focused on the hydrate crystal growth at the gas/water interface or surface of water droplets. However, this study monitors crystal growth at the bubble surface. In the case of pure water, smooth hydrate film was formed initially and the film surface on the bubble became rough as experiment proceeded. It was also observed that the hydrate crystals developed as the dendritic shape from the surface of hydrate film. In the presence of SDS, drastic changes in morphology were observed in that smoke-like crystals appeared from the top of the bubble. Besides, the gas bubble was not fully covered by hydrate film when the SDS concentration increased. In the PVCap solution, seed-like or small spot of hydrate crystals occurred sparsely on the bubble surface and spread out the whole surface as experiment progressed. The experimental results showed that the presence of SDS or PVCap affect morphological characteristics of methane–propane hydrate crystal on the surface of gas bubble.

Spherical biphasic calcium phosphate (BCP) micro-granules consisting of hydroxyapatite (HAp) and tricalcium phosphate (TCP) were prepared using a rotary spray drying and sintering process. A significant phase transformation of TCP in BCP granules occurred according to the relative content of HAp and TCP in the BCP granules depending on the sintering temperature. The crystal growth of HAp in BCP was suppressed by a phase transformation of TCP with a change in the electron density distribution in a crystal unit cell. In addition, these progressive changes in the hydroxyl and phosphate group of BCP granules might be due to the phase transformation of TCP. Consequently, such structural changes in the BCP granules led to an unexpected change in granule size and micro-cracks on their surface at high temperatures.

Spherical tricalcium phosphate (TCP) micro-granules were prepared using a jet wheel impact atomization and calcination process. Spherical TCP granules were obtained which can exhibit phase transformation between the alpha and beta polymorphs as a function of the heating temperature. The progressive changes in the phosphate group of TCP granules were attributed to the phase transformation. Consequently, such structural changes in the TCP micro-granules can be used to control the dissolution and degradation of TCP through the controlled density and microporosity of the micro-granules.

In-depth understanding of the CH4 hydrate formation and decomposition processes is essential for energy recovery as well as related transportation/storage technologies. Raman spectroscopy is well suited for hydrate studies of aqueous-hydrate conditions, because it is not susceptible to interference from aqueous environments. In order to obtain more specific and ongoing information on the CH4 hydrate formation and dissociation, two different in-situ Raman spectroscopies with specially designed fiber-optic probes were used in a semi-batch stirred reactor (total volume 365 mL). With these arrangements, it was possible to obtain macroscopic (gas uptake, releasing, CH4 solubility) and microscopic (structural, cage occupancy, water structure) data simultaneously during CH4 hydrate formation and decomposition. Based on in-situ Raman observations, we are able to determine the time-dependent encapsulation of CH4 in large and small cage through hydrate formation and decomposition. In all experiments, the Raman intensity of the OH-stretching band (3000–3800 cm−1) was significantly reduced or increased at the point where hydrates were formed or dissociated, which is expected to provide valuable information for further hydrogen-bond research including hydrate study. In addition, in-situ Raman spectroscopy was used to determine the concentration of dissolved CH4 under hydrate formation/decomposition conditions and the results were in good agreement with experimental data in the literature.

Potential application of gas hydrate-based desalination was suggested with a novel apparatus design. The equipment continuously produces and pelletizes CO2 hydrates by a squeezing operation of a dual cylinder unit, which is able to extract hydrate pellets from the reactor containing hydrate slurries. Removal efficiencies for each dissolved mineral from seawater samples was also tested by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) analysis. In a single-stage hydrate process, 72–80% of each dissolved mineral was removed in the following order: K+ > Na+ > Mg2+ > B3+ > Ca2+. Our results also showed that ion rejection by the hydrate process strongly depends on the ionic size and charge. This study illustrates that the suggested method and apparatus may solve the separation difficulty between hydrate crystals and concentrated brine solutions, thus it can be applied for more effective desalination processes.

This paper reports an experimental study on the effects of novel anionic multichain disulfonate surfactant on the formation of methane gas hydrate. A series of surfactants with sodium sulfonic acid groups and different hydrophobic carbon chain lengths (C 8 , C 10 , and C 12 ) were synthesized, and the effects of carbon chain length and concentration on methane hydrate formation kinetics were systematically investigated. Methane hydrate formation was conducted in a magnetic stirred vessel at the constant temperature of 274.15 K and in a pressure range of 3.5–4.0 MPa. All surfactants showed kinetic promoting behavior for methane gas hydrate formation, and the surfactant with the shortest chain length showed the highest acceleration effect. In addition, this multichain disulfonate surfactant exhibited higher methane storage capacity than SDS (sodium dodecyl sulfate) even at lower surfactant concentration, due to its lower critical micelle concentration (CMC) and the surface tension itself of the Gemini-type multichain surfactant.

In this study, we investigated the effect of tetra-n-butyl ammonium bromide (TBAB) on separation and/or collection of CO2 from CO2/H2 (40:60) gas mixture via hydrate crystallization. The phase equilibrium conditions shifted to milder conditions as increasing the amount of TBAB additive up to 3.0 mol%. The existence of the critical concentration of the additive effects on the phase equilibrium conditions was also observed. The hydrate formation rate in 1.0 mol% TBAB solution showed the highest value while the hydrate formation rate in 3.0 mol% TBAB solution showed the lowest value. Raman analyses revealed that only CO2 gas molecules enclathrated under experimental conditions carried out in this study. The phase equilibrium temperature of CO2–H2 (40:60) mixture gas hydrate systems with TBAB additive located in the range of between 283 and 290 K at the integrated gasification combined cycle (IGCC) process pressure range of 2.5–5.0 MPa. This study provides the potential of hydrate process to separate the CO2 gas from CO2–H2 (40:60) mixture gas in IGCC process without significantly lowering the processing temperature.

In this study, gas hydrate from CO 2 /H 2 gas mixtures with the addition of tetrahydrofuran (THF) was formed in a semi-batch stirred vessel at various pressures and temperatures to investigate the CO 2 separation/recovery properties. This mixture is of interest to CO 2 separation and recovery from Integrated Gasification Combine Cycle (IGCC) power plants. During hydrate formation the gas uptake was determined and composition changes in the gas phase were obtained by gas chromatography. The impact of THF on hydrate formation from the CO 2 /H 2 was observed. The addition of THF significantly reduced the equilibrium formation conditions. 1.0 mol% THF was found to be the optimum concentration for CO 2 capture based on kinetic experiments. The present study illustrates the concept and provides thermodynamic and kinetic data for the separation/recovery of CO 2 (pre-combustion capture) from a fuel gas (CO 2 /H 2 ) mixture.

The hydrate phase behavior of CO 2 /3-methyl-1-butanol (3M1B)/water, CO 2 /tetrahydrofuran (THF)/water and CO 2 /1,4-dioxane (DXN)/water was investigated using both a high-pressure equilibrium viewing cell and a kinetic pressure–temperature measurement system with a constant volume. The dissociation pressures of CO 2 /3M1B/water were identical to those of pure CO 2 hydrate, indicating that CO 2 is not acting as a help gas for structure H hydrate formation with 3M1B, thus the formed hydrate is pure CO 2 structure I hydrate. The CO 2 molecules could be encaged in small cages of the structure II hydrate framework formed with both of THF and DXN. For a stoichiometric ratio of 5.56 mol% THF, we found a large shift of dissociation boundary to lower pressures and higher temperatures from the dissociation conditions of pure CO 2 hydrate. From the measurements using the kinetic pressure–temperature system, it was found that the solid binary hydrate samples formed from off-stoichiometric THF and DXN aqueous solutions are composed of pure CO 2 hydrate with a hydrate number n =7.0 and THF/CO 2 and DXN/CO 2 binary hydrates with a molar ratio of x CO 2 ·THF·17H 2 O and x CO 2 ·DXN·17H 2 O, respectively. The X-ray diffraction was used to identify the binary hydrate structure and Raman spectroscopy was measured to support the phase equilibrium results and to investigate the occupation of CO 2 molecules in the cages of the hydrate framework.

Sulfur hexafluoride (SF(6)) has been widely used in a variety of industrial processes, but it is one of the most potent greenhouse gases. For this reason, it is necessary to separate or collect it from waste gas streams. One separation method is through hydrate crystal formation. In this study, SF(6) hydrate was formed in aqueous surfactant solutions of 0.00, 0.01, 0.05, 0.15 and 0.20 wt% to investigate the effects of surfactants on the hydrate formation rates. Three surfactants, Tween 20 (Tween), sodium dodecyl sulfate (SDS) and linear alkyl benzene sulfonate (LABS), were tested in a semi-batch stirred vessel at the constant temperature and pressures of 276.2 K and 0.78 MPa, respectively. All surfactants showed kinetic promoter behavior for SF(6) hydrate formation. It was also found that SF(6) hydrate formation proceeded in two stages with the second stage being the most rapid. In situ Raman spectroscopy analysis revealed that the increased gas consumption rate with the addition of surfactant was possibly due to the increased gas filling rate in the hydrate cavity.

The influence of the kinetic inhibitor poly( N -vinylpyrrolidone) or PVP on hydrate methane/propane hydrate formation was studied in pre-saturated liquid water with and without the presence of heptane under different undercooling conditions. It was found that when the inhibitor concentration was 0.1 wt%, hydrate formation started as a film at the gas/water interface similar to the crystal behavior without inhibitor. When the inhibitor concentration was 0.5 wt% hydrate formation started at the wall above the gas/water interface and the hydrate film at the gas/water interface was observed as well. However, for inhibitor concentration 1.0 wt%, the hydrate started forming from water droplets attached to the wall above the gas/liquid interface and grew catastrophically. When the inhibitor concentration was 0.1 wt% and undercooling was 13.7 or 8.1 K whiskery or fiber-type hydrate crystals, respectively, were seen within the liquid pool. This morphology was not observed in the absence of PVP. When inhibitor concentration was 0.5 or 1.0 wt% or undercooling was 3.2 K, there was no crystal growth within the liquid pool. Floating crystals were also observed, but were needle-type and thus different from the equiaxed floating crystals found in the system without the inhibitor.

This work investigated the kinetic inhibiting effect of a number of cationic starches in hydrate formation experiments with methane and methane/ethane and methane/propane gas mixtures. The starches were found to exhibit a very weak inhibiting effect except for tapioca starch which increased the induction time (delay of onset of crystallization) by an order of magnitude. The addition of polyethylene oxide (PEO) was found to further enhance the performance of tapioca starch as well as some of the other starches. Finally, the presence of tapioca starch and PEO was found to suppress the memory effect. The results were interpreted based on a mechanism proposed by Zeng et al. [2006a. Effect of antifreeze protein on nucleation, growth and memory of gas hydrates. A.I.Ch.E. Journal 52(9), 3304–3309; 2006b. Effect of antifreeze proteins on the nucleation, growth and the memory during tetrahydrofuran clathrate hydrate formation. Journal of the American Chemical Society 128, 2844–2850] whereby the starches interfere with nucleation through interactions with heterogeneous nucleation sites.

Gas hydrate formation experiments were conducted with a methane–ethane mixture at 273.7 or 273.9 K and 5100 kPa and using water droplets or water contained in cylindrical glass columns. The effect of kinetic inhibitors and the water/solid interface on the induction time for hydrate crystallization and on the hydrate growth and decomposition characteristics was studied. It was found that inhibitors GHI 101 and Luvicap EG delayed the onset of hydrate nucleation. While this inhibition effects has been reported previously some unusual behaviour was observed and reported for the first time. In particular, the water droplet containing GHI 101 or Luvicap EG was found to collapse prior to nucleation and spread out on the Teflon surface. Subsequently, hydrate was formed as a layer on the surface. Catastrophic growth and spreading of the hydrate crystals was also observed during hydrate formation in the glass columns in the presence of the kinetic inhibitor. Finally, when polyethylene oxide (PEO) was added into the kinetic inhibitor solution the memory effect on the induction time decreased dramatically.

Inclusion of polyethylene oxide into a kinetic inhibitor solution was found to enhance the performance of the inhibitor. Polyethylene oxide is a commercially available high molecular weight polymer that is not a kinetic inhibitor by itself. The hydrate formation experiments in the presence of the various inhibitor solutions were conducted in a vessel in a semi-batch manner at constant pressure and using methane and methane–ethane gas mixtures. In some experiments a non-aqueous liquid phase ( n -heptane) was also present. The induction time, the gas uptake and the temperature were measured. It was found that the induction time is prolonged in the presence of the additive by an order of magnitude in some cases compared to the inhibitor only.

Gas hydrate formation and decomposition on water droplets using an 89.4% methane—10.6% ethane mixture, and a 90.1% methane—9.9% propane mixture were carried out in a new apparatus suitable for morphology studies. As expected the induction time was found to be much shorter when the water had hydrate memory. All droplets nucleated simultaneously and the droplet size and shape had no noticeable effect on induction time and macroscopic crystal growth morphology for hydrates from the methane–ethane mixture. However, the surface of the hydrate crystals from methane–propane had a “hairy-like” appearance which changed to a smooth surface over time. Moreover, the smaller droplets during hydrate reformation showed an extensive hydrate growth and looked like snow-flakes. Sequential pictures generated by time-lapse videos showed that the time required for hydrate to cover the water droplet surface ranged from 10 to 23 s and was shorter when there was gas-phase agitation (mixing). The growth is postulated to occur in two stages. The first stage lasts about 10–23 s and growth takes place laterally. Growth takes place at the hydrate/gas and the hydrate/water interfaces during the second stage. The implication of the findings for process design of hydrate formation vessels is also discussed.

Liquid–liquid equilibrium (LLE) data for non-aqueous liquid (neohexane [NH], tert-butyl methyl ether [TBME], methylcyclohexane [MCH], or n-heptane [nC7]) and water have been measured under atmospheric pressure at 275.5, 283.15, and 298.15 K. It was found that TBME is the most water soluble followed by NH, MCH, and nC7. As the temperature increased, the solubility of the non-aqueous liquids (NALs) in water decreased. The solubility of water in the non-aqueous liquid was found to increase in the following order: MCH

Corrigendum to ‘‘Thermodynamic stability, spectroscopic identification and cage occupation of binary CO2 clathrate hydrates’’ [Chem. Eng. Sci. (2009) 5125–5130] Hyung Joon Shin , Yun-Je Lee , Jun-Hyuck Im , Kyu Won Han , Jong-Won Lee , Yongjae Lee , Ju Dong Lee , Won-Yil Jang , Ji-Ho Yoon a, a Department of Energy and Resources Engineering, Korea Maritime University, Busan 606-791, Republic of Korea b Department of Environmental Engineering, Kongju National University, Chungnam 330-717, Republic of Korea c Department of Earth System Sciences, Yonsei University, Seoul 120749, Republic of Korea d Busan R&D Center, Korea Institute of Industrial Technology, Busan 609-735, Republic of Korea