Dataset on investigating nucleation and growth kinetics of methane hydrate in aqueous methanol solutions.

This work systematically investigates the effect of methanol (MeOH) in a wide range of concentrations (0, 1, 2.5, 5, 10, 20, 30, 40, and 50 mass%) on methane hydrate nucleation and growth kinetics. Multiple measurements of gas hydrate onset temperatures and pressures for CH4-H2O and CH4-MeOH-H2O systems were performed by ramp cooling experiments (1 K/h) using sapphire rocking cell RCS6 apparatus. The dataset comprises 96 ramp experiments conducted under identical initial conditions for each solution (gas pressure of 8.1 MPa at 295 K). The reported hydrate onset temperatures and pressures range within 248-282 K and 6.2-7.5 MPa, respectively. The methane hydrate onset subcooling was calculated using literature data on the three-phase gas-aqueous solution-gas hydrate equilibrium for the studied systems. The study determined the numerical values of the shape and scale parameters of gamma distributions that describe the empirical dependences of methane hydrate nucleation cumulative probability as a function of hydrate onset subcooling in the aqueous methanol solutions. Gas uptake curves were analyzed to characterize the kinetics of methane hydrate growth under polythermal conditions at different methanol concentrations.

Data on searching for synergy between alcohol and salt to produce more potent and environmentally benign gas hydrate inhibitors.

In order to systematically study the synergistic effect of gas hydrate inhibition with mixtures of methanol (MeOH) and magnesium chloride (MgCl2), the impact of these compounds on the thermodynamic stability of methane hydrate in the systems of CH4-MeOH-H2O, CH4-MgCl2-H2O, and CH4-MeOH-MgCl2-H2O was experimentally investigated. The pressure and temperature conditions of the three-phase vapor-aqueous solution-gas hydrate equilibrium were determined for these systems. The resulting dataset has 164 equilibrium points within the range of 234-289 K and 3-13 MPa. All equilibrium points were measured as the endpoint of methane hydrate dissociation during the heating stage. The phase boundaries of methane hydrate were identified for 8 systems with MeOH (up to 60 mass%), 5 MgCl2 solutions (up to 26.7 mass%), and 14 mixtures of both inhibitors. Most equilibrium points were measured using a ramp heating technique (0.1 K/h) under isochoric conditions when the fluids were stirred at 600 rpm. It was found that even a 0.5 K/h heating rate for the CH4-MgCl2-H2O system at low salt concentrations, along with all mixed aqueous solutions with methanol, gives results that do not differ from 0.1 K/h, considering the measurement uncertainties. Most measurements for the CH4-MgCl2-H2O system at high salt content were acquired using a step heating technique. The coefficients of the empirical equations approximating the equilibrium points for each inhibitor concentration were defined. The change in the slope parameter of the empirical equation was analyzed as a function of inhibitor content. Correlations that accurately describe the thermodynamic inhibition effect of methane hydrate with methanol and magnesium chloride on a mass% and mol% scale were obtained. The freezing temperatures of single and mixed aqueous solutions of methanol and magnesium chloride were determined experimentally to confirm the thermodynamic consistency of the methane hydrate equilibrium data.

Polyurethane/n-Octadecane Phase-Change Microcapsules via Emulsion Interfacial Polymerization: The Effect of Paraffin Loading on Capsule Shell Formation and Latent Heat Storage Properties.

Organic phase-change materials (PCMs) hold promise in developing advanced thermoregulation and responsive energy systems owing to their high latent heat capacity and thermal reliability. However, organic PCMs are prone to leakages in the liquid state and, thus, are hardly applicable in their pristine form. Herein, we encapsulated organic PCM n-Octadecane into polyurethane capsules via polymerization of commercially available polymethylene polyphenylene isocyanate and polyethylene glycol at the interface oil-in-water emulsion and studied how various n-Octadecane feeding affected the shell formation, capsule structure, and latent heat storage properties. The successful shell polymerization and encapsulation of n-Octadecane dissolved in the oil core was verified by confocal microscopy and Fourier-transform infrared spectroscopy. The mean capsule size varied from 9.4 to 16.7 µm while the shell was found to reduce in thickness from 460 to 220 nm as the n-Octadecane feeding increased. Conversely, the latent heat storage capacity increased from 50 to 132 J/g corresponding to the growth in actual n-Octadecane content from 25% to 67% as revealed by differential scanning calorimetry. The actual n-Octadecane content increased non-linearly along with the n-Octadecane feeding and reached a plateau at 66-67% corresponded to 3.44-3.69 core-to-monomer ratio. Finally, the capsules with the reasonable combination of structural and thermal properties were evaluated as a thermoregulating additive to a commercially available paint.

Dataset for the experimental study of dimethyl sulfoxide as a thermodynamic inhibitor of methane hydrate formation.

To determine the ability of dimethyl sulfoxide (DMSO) to inhibit methane hydrate formation by the thermodynamic mechanism, we measured the pressures and temperatures of monovariant equilibrium of three phases: gaseous methane, aqueous DMSO solution, and methane hydrate. A total of 54 equilibrium points were obtained. Hydrate equilibrium conditions have been measured for eight different concentrations of dimethyl sulfoxide ranging from 0 to 55 mass%, at temperatures of 242-289 K and pressures of 3-13 MPa. Measurements were performed in an isochoric autoclave (volume of 600 cm3, inside diameter of 8.5 cm) at a heating rate of 0.1 K/h and intense fluid agitation (600 rpm) with four-blade impeller (diameter of 6.1 cm, blade height of 2 cm). The specified stirring speed for aqueous DMSO solutions at 273-293 K is equivalent to a range of Reynolds numbers of 5.3‧103-3.7‧104. The endpoint of methane hydrate dissociation at defined temperature and pressure values was taken as the equilibrium point. The anti-hydrate activity of DMSO was analyzed on a mass% and mol% scale. Precise correlations between the thermodynamic inhibition effect of dimethyl sulfoxide ΔTh and the influencing factors (DMSO concentration and pressure) were derived. Powder X-ray diffractometry was employed to examine the phase composition of the samples at 153 K. Measurement of ice freezing points in aqueous solutions of dimethyl sulfoxide (up to 50 mass%) at ambient pressure allowed us to clarify the location of the liquidus line in the DMSO-H2O system and to check the hydrate equilibrium data for thermodynamic consistency.

Dataset for the phase equilibria and PXRD studies of urea as a green thermodynamic inhibitor of sII gas hydrates.

The equilibrium conditions of sII methane/propane hydrates have been experimentally determined for the C3H8/CH4-H2O-urea system. The equilibrium dissociation temperatures and pressures of sII hydrates span a wide P,T-range (266.7-293.9 K; 0.87-9.49 MPa) and were measured by varying the feed mass fraction of urea in solution from 0 to 50 mass%. The experimental points at feed urea concentration ≤ 40 mass% correspond to the V-Lw-H equilibrium (gas-aqueous urea solution-gas hydrate). A four-phase V-Lw-H-Su equilibrium (with an additional phase of solid urea) was observed because the solubility limit of urea in water was reached for all points at a feed mass fraction of 50 mass% and for one point at 40 mass% (266.93 K). Gas hydrate equilibria were measured using a high-pressure rig GHA350 under isochoric conditions with rapid fluid stirring and slow ramp heating of 0.1 K/h. Each measured point represents complete dissociation of the sII hydrate. The phase equilibrium data was compared with the literature reported for the C3H8/CH4-H2O and CH4-H2O-urea systems. A comprehensive analysis of the thermodynamic inhibition effect of urea to sII C3H8/CH4 hydrates on pressure and concentration of the inhibitor was carried out. The phase composition of the samples was analyzed by powder X-ray diffractometry at 173 K.

Dataset for the new insights into methane hydrate inhibition with blends of vinyl lactam polymer and methanol, monoethylene glycol, or diethylene glycol as hybrid inhibitors.

Three-phase equilibrium conditions of vapor-aqueous solution-gas hydrate coexistence for the systems of CH4-H2O-organic thermodynamic inhibitor (THI) were experimentally determined. Hydrate equilibrium measurements for systems with methanol (MeOH), monoethylene glycol (MEG), and diethylene glycol (DEG) were conducted. Five concentrations of each inhibitor (maximum content 50 mass%) were studied in the pressure range of 4.9-8.4 MPa. The equilibrium temperature and pressure in the point of complete dissociation of methane hydrate during constant-rate heating combined with vigorous mixing of fluids (600 rpm) in a high-pressure vessel were determined. We compared our experimental points with reliable literature data. The coefficients of empirical equations are derived, which accurately describe hydrate equilibrium conditions for the studied systems. The effect of THI concentration and pressure on methane hydrate equilibrium temperature suppression was analyzed. In the second stage, we studied the kinetics of methane hydrate nucleation/growth in systems containing a polymeric KHI (0.5 mass% of N-vinylpyrrolidone and N-vinylcaprolactam copolymer) in water or THI aqueous solution. For this, temperatures, pressures, and subcoolings of methane hydrate onset were measured by rocking cell tests (RCS6 rig, ramp cooling at 1 K/h). Gas uptake curves characterizing the methane hydrate crystallization kinetics in the polythermal regime were obtained.

Dataset for the dimethyl sulfoxide as a novel thermodynamic inhibitor of carbon dioxide hydrate formation.

The temperatures and pressures of the three-phase equilibrium V-Lw-H (gas - aqueous solution - gas hydrate) were measured in the CO2 - H2O - dimethyl sulfoxide (DMSO) system at concentrations of organic solute in the aqueous phase up to 50 mass%. Measurements of CO2 hydrate equilibrium conditions were carried out using a constant volume autoclave by continuous heating at a rate of 0.1 K/h with simultaneous stirring of fluids by a four-blade agitator at 600 rpm. The equilibrium temperature and pressure of CO2 hydrate were determined for the endpoint of the hydrate dissociation in each experiment. The CO2 gas fugacity was calculated by the equation of state for carbon dioxide for the measured points. The flow regime in the autoclave during the operation of the stirring system was characterized by calculating the Reynolds number using literature data on the viscosity and density of water and DMSO aqueous solutions. We employed regression analysis to approximate the dependences of equilibrium pressure (CO2 gas fugacity) on temperature by two- and three-parameter equations. For each measured point, the value of CO2 hydrate equilibrium temperature suppression ΔTh was computed. The dependences of this quantity on CO2 gas fugacity are considered for all DMSO concentrations. The coefficients of empirical correlation describing ΔTh as a function of the DMSO mass fraction in solution and the equilibrium gas pressure are determined. This article is a co-submission with a paper [1].

Dataset for the interfacial tension and phase properties of the ternary system water - 2-butoxyethanol - toluene.

Two-phase samples containing water, 2-butoxyethanol, and toluene in the different mass ratios were gravimetrically prepared in the jacketed cells at T=293.15 K and p=0.100 MPa and equilibrated for 24 h. The samples were volumetrically titrated until homogeneous. Then new samples were prepared in the two-phase region with compositions in the immediate proximity to the expected separation boundary and titrated until homogeneous. The critical point was located, keeping the phase ratio of 1:1 during the titration. The density of homogeneous samples obtained during titration was measured using the density meter. These data were used to construct an interpolation of the density along the separation boundary. New two-phase samples were prepared; the interfacial tension, density, and viscosity were measured. Thus, interfacial tension isotherm and viscosity isotherm were obtained using density interpolation to determine the composition of the equilibrated phases. The obtained data can be used to prepare the two-phase samples with desired properties, design the oil-water separation processes, and develop new oil spill dispersants containing 2-butoxyethanol. This article is a co-submission with a paper [1].

Performance of Waterborne Polyurethanes in Inhibition of Gas Hydrate Formation and Corrosion: Influence of Hydrophobic Fragments.

The design of new dual-function inhibitors simultaneously preventing hydrate formation and corrosion is a relevant issue for the oil and gas industry. The structure-property relationship for a promising class of hybrid inhibitors based on waterborne polyurethanes (WPU) was studied in this work. Variation of diethanolamines differing in the size and branching of N-substituents (methyl, n-butyl, and tert-butyl), as well as the amount of these groups, allowed the structure of polymer molecules to be preset during their synthesis. To assess the hydrate and corrosion inhibition efficiency of developed reagents pressurized rocking cells, electrochemistry and weight-loss techniques were used. A distinct effect of these variables altering the hydrophobicity of obtained compounds on their target properties was revealed. Polymers with increased content of diethanolamine fragments with n- or tert-butyl as N-substituent (WPU-6 and WPU-7, respectively) worked as dual-function inhibitors, showing nearly the same efficiency as commercial ones at low concentration (0.25 wt%), with the branched one (tert-butyl; WPU-7) turning out to be more effective as a corrosion inhibitor. Commercial kinetic hydrate inhibitor Luvicap 55 W and corrosion inhibitor Armohib CI-28 were taken as reference samples. Preliminary study reveals that WPU-6 and WPU-7 polyurethanes as well as Luvicap 55 W are all poorly biodegradable compounds; BODt/CODcr (ratio of Biochemical oxygen demand and Chemical oxygen demand) value is 0.234 and 0.294 for WPU-6 and WPU-7, respectively, compared to 0.251 for commercial kinetic hydrate inhibitor Luvicap 55 W. Since the obtained polyurethanes have a bifunctional effect and operate at low enough concentrations, their employment is expected to reduce both operating costs and environmental impact.

Analysis of Natural Gas Using a Portable Hollow-Core Photonic Crystal Coupled Raman Spectrometer.

The low accessibility of natural gas fields and transporting pipelines requires portable online analyzers of the composition of natural gas, ensuring nearly chromatographic precision and capable of in situ analysis of a wide range of gases, including infrared-inactive ones (hydrogen, oxygen, nitrogen, chlorine). We have developed an express method of gas analysis meeting all the requirements for analysis of natural gas and its derivative mixtures using a portable 532 nm Raman spectrometer rigidly connected to a hollow-core crystal photonic fiber.

Freezing-Induced Loading of TiO2 into Porous Vaterite Microparticles: Preparation of CaCO3/TiO2 Composites as Templates To Assemble UV-Responsive Microcapsules for Wastewater Treatment.

The photocatalytic degradation of organic molecules is one of the effective ways for water purification. At this point, photocatalytic microreactor systems seem to be promising to enhance the versatility of the photoassisted degradation approach. Herein, we propose photoresponsive microcapsules prepared via layer-by-layer assembly of polyelectrolytes on the novel CaCO3/TiO2 composite template cores. The preparation of CaCO3/TiO2 composite particles is challenging because of the poor compatibility of TiO2 and CaCO3 in an aqueous medium. To prepare stable CaCO3/TiO2 composites, TiO2 nanoparticles were loaded into mesoporous CaCO3 microparticles with a freezing-induced loading technique. The inclusion of TiO2 nanoparticles into CaCO3 templates was evaluated with scanning electron microscopy and elemental analysis with respect to their type, concentration, and number of loading iterations. Upon polyelectrolyte shell assembly, the CaCO3 matrix was dissolved, resulting in microreactor capsules loaded with TiO2 nanoparticles. The photoresponsive properties of the resulted capsules were tested by photoinduced degradation of the low-molecule dye rhodamine B in aqueous solution and fluorescently labeled polymer molecules absorbed on the capsule surface under UV light. The exposure of the capsules to UV light resulted in a pronounced degradation of rhodamine B in capsule microvolume and fluorescent molecules on the capsule surface. Finally, the versatility of preparation of multifunctional photocatalytic and magnetically responsive capsules was demonstrated by iterative freezing-induced loading of TiO2 and magnetite Fe3O4 nanoparticles into CaCO3 templates.

Generic Nature of Interfacial Phenomena in Solutions of Nonionic Hydrotropes.

Nonionic hydrotropes (low-molecular-weight amphiphiles) demonstrate striking dual actions in bulk solutions and interfaces, exhibiting both surfactant-like and co-solvent properties. We report on peculiar, strongly affected by this duality, liquid-liquid and air-liquid-liquid interfacial behavior in aqueous ternary systems, containing hydrotropes and hydrocarbons, in a broad range of compositions and at various temperatures. Phase diagrams of the studied systems, containing tertiary butanol (TBA), as a hydrotrope, are of Type 1: the hydrotrope, at the experimental conditions, is completely miscible with water and with all investigated hydrocarbons [cyclohexane (CHX), toluene (TOL), and n-decane (DEC)], whereas the ternary mixtures exhibit liquid-liquid phase separation terminated at corresponding critical points. The shape and location of the phase separation boundary are only weakly dependent on temperature and the hydrocarbon's nature; however, the critical point in the water-TBA-DEC system is significantly shifted toward a higher TBA concentration. For the experimentally studied systems and for available data reported in the literature, we confirmed an apparently generic (for nonionic hydrotropes) phenomenon of a dual action at water-oil interfaces (earlier found in water-TBA-CHX [J. Phys. Chem. C 2017, 121, 16423]): at low concentrations, hydrotropes saturate the water-oil interface like a surfactant, whereas at higher concentrations they act as co-solvents, resulting in vanishing interfacial tension at the liquid-liquid critical point. We suggest a universal crossover function that accurately interpolates the two theoretically based limits of interfacial behavior. This crossover function also accounts for earlier deviations from Langmuir-von Szyszkowski limiting behavior in the water-TBA-DEC system, caused by lower solubility (relative to other studied hydrocarbons) of DEC in water. An intriguing correlation between the dual action of hydrotropes at the water-oil interface and the behavior of the liquid-air interfaces is also discussed.