Search

Lopinavir is a potent protease inhibitor that is used as a first-line pharmaceutical drug for the treatment of HIV. The multi-component solvated Lopinavir crystal, systematic name (2S)-N-[(2S,4S,5S)-5-[2-(2,6-dimethylphenoxy)acetamido]-4- hydroxy-1,6-diphenylhexan-2-yl]-3-methyl-2-(2-oxo-1,3-diazinan-1-yl)butanamide–ethane-1,2-diol–water (8/3/7) 8C37H48N4O5·3C2H6O2·7H2O, was prepared using evaporative methods. The crystalline material obtained from this experimental synthesis was characterized and elucidated by single-crystal X-ray diffraction (SC-XRD). The crystal structure is unusual in that the unit cell contains 18 molecules. The stoichiometric ratio of this crystal is eight Lopinavir molecules [8(C37H48N4O5)], three ethane-1,2-diol molecules [3(C2H6O2)] and seven water molecules [7(H2O)]. The crystal packing features both bi- and trifurcated hydrogen bonds between atoms. [ABSTRACT FROM AUTHOR]

The title compound, a hydrate of 3,5-diamino-1,2,4-triazole (DATA), C2H5N5·H2O, was synthesized in the presence of sodium perchlorate. The evaporation of H2O from its aqueous solution resulted in anhydrous DATA, suggesting that sodium perchlorate was required to precipitate the DATA hydrate. The DATA hydrate crystallizes in the P21/c space group in the form of needle-shaped crystals with one DATA and one water molecule in the asymmetric unit. The water molecules form a three-dimensional network in the crystal structure. Hirshfeld surface analysis revealed that 8.5% of the intermolecular interactions originate from H···O contacts derived from the incorporation of the water molecules. [ABSTRACT FROM AUTHOR]

This study investigates the natural gas hydrates within the Qiongdongnan Basin by integrating well-log and seismic data. Through pre-stack inversion and rock physics analysis, key parameters such as P-wave and S-wave impedances were utilized to distinguish hydrate-bearing formations from other geological bodies. A low-frequency model was constructed using the Inverse Distance Weighting (IDW) algorithm to improve the precision of parameter inversion. This study employs a multi-constraint inversion strategy, incorporating hard constraints from multiple wells and soft constraints from geological frameworks, ensuring reliable inversion results. Findings indicate that hydrate reservoirs are characterized by increased wave velocity and density due to hydrate accumulation, providing insights into the spatial distribution and characteristics of hydrates. This research enhances the understanding of hydrate reservoirs and offers valuable data for exploration in the Qiongdongnan Basin. [ABSTRACT FROM AUTHOR]

Estimation of the porosity of a hydrate reservoir is essential for its exploration and development. However, the estimation accuracy was usually less certain in most previous studies that simply assumed that there is a linear relationship between the porosity and single‐elastic wave velocities or other rock physical parameters, thus affecting the evaluation of the reserves. In the three‐phase Biot‐type equations that are fundamental to model a hydrate‐bearing reservoir, porosity, alongside hydrate saturation, mineral constituent proportions and hydrate–grain contact factor, is non‐linearly responded by density, compressional and shear wave velocities. To improve porosity estimation, we propose to invert simultaneously four‐parameter (porosity, hydrate saturation, mineral constituent proportions and hydrate–grain contact factor) using an iteratively nonlinear interior‐point optimization algorithm to solve a nonlinear objective function that is a summation of the squared misfits between the well log and three‐phase Biot‐type equation–modelled density, compressional and shear wave velocities. A test in Mount Elbert gas hydrate research well was conducted for the case of a gas hydrate stratigraphic test well where elastic wave velocities, density, porosity and mineral composition analysis data are available. The four‐parameter inversion yielded a lower root mean square error for porosity (0.0245) across the entire well‐logging section compared to previous estimations from the linear relationship, post‐stacked and pre‐stacked seismic traces as well as the pore‐filling effective medium theory model applied to other well cases. Additionally, the other three parameters demonstrated good agreement with well logs. Inversion tests conducted at three additional hydrate sites also produced accurate results. Consequently, the new method surpasses previous approaches in porosity estimation accuracy. [ABSTRACT FROM AUTHOR]

The development of flow assurance technology in submarine pipelines affects the safety, efficiency, and economy of deepwater natural gas development. In this study, in order to accurately predict the hydrate formation risk in deepwater submarine pipelines, a novel mathematical prediction model of hydrate formation risk has been established. The model has been applied and sensitivity analysis of typical factors has been carried out. The model prediction results show that: (1) Due to the low temperature of the seabed, hydrate formation region (HFR) often exists in submarine pipelines. (2) When other conditions are constant, hydrate formation region increases with the decrease in seawater temperature. (3) When other conditions are constant, the temperature drop, and the length of hydrate formation region decrease with the increase of gas transmission rate. (4) When other conditions are constant, the temperature drop, and the length of hydrate formation region decreases with the increase of gas transport temperature. (5) Reasonable setting of gas transmission temperature and gas transmission rate can help to reduce the hydrate risk and consumption of inhibitors during submarine natural gas transmission. Highlights: The hydrate risk prediction model for submarine pipeline is established. The model has been applied in submarine pipeline natural gas transmission. The T-P distribution characteristics in submarine pipeline are analyzed. The hydrate formation region in submarine pipeline is determined. [ABSTRACT FROM AUTHOR]

At present, the problem of global warming is becoming increasingly serious, and one of the main culprits is the increasing amount of carbon dioxide emissions. Although the traditional carbon capture technologies can reduce the concentration of CO2 in the atmosphere, it has a series of problems such as high energy consumption, high cost, low efficiency or unfriendly environment. Hydrate-based carbon dioxide separation are considered to be a technology with great application and development prospects. Compared with the traditional method of carbon dioxide separation, the hydrate method has the advantages of simple process, low energy consumption and environmental friendliness. This review introduces the advantages of hydrate method compared with traditional carbon capture technologies, expounds the theory of carbon dioxide capture by hydrate, and the strengthening and improvement techniques of hydrate method, including thermodynamic promoter, kinetic promoter and mechanical reinforcement, and introduces the practical application of hydrate method in various fields. [ABSTRACT FROM AUTHOR]

The article in the journal "Frontiers in Earth Science" explores contemporary studies on cold seeps, hydrothermal vents, mud volcanoes, and related seafloor features. These features provide insights into deep processes that are typically inaccessible to scientists. The research emphasizes multidisciplinary approaches to studying seafloor fluid emissions, highlighting the importance of geologic, physical, chemical, and biological processes in these environments. The studies cover a wide range of topics, including microbial processes, fluid dynamics, mineralization, and the role of seafloor emissions in global biogeochemical cycles. [Extracted from the article]

A variable or non-stoichiometric hydrate of GDC-4379 was developed into a formulated capsule with a 1% drug loading. The water content of this hydrate varied from 0-0.7 moles over the relative humidity (RH) range of 0-98% (25°C). Since a variable state of hydration coupled with rapid equilibration of lattice water with the environmental RH can lead to challenges in formulation development, an analytical method to directly and accurately determine the state of hydration of the active in such a low dose formulation was deemed necessary. Owing to its high selectivity and fast acquisition times, 19F solid-state NMR was effectively utilized to directly determine the lattice water content of the active in the formulated capsule. By correlating Δδ, the chemical shift difference between the isotropic peaks, with the relative humidity and ultimately the lattice water content, the state of hydration of GDC-4379 in the formulated capsule was experimentally determined as 0.63 moles of water/mole of anhydrate. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Carbon sequestration technology offers a solution to mitigate excessive carbon dioxide emissions and sustainable development in the future. This study proposes a method for subsea carbon sequestration through the injection of cold seawater to promote CO2 hydrate formation. Using a self-developed simulator, we modeled and calculated the long-term sequestration process. The study focuses on analyzing the thermal regulation of the seabed following cold seawater injection, the multiphysical field evolution during CO2 injection and long-term sequestration, and the impact of seawater injection volumes on sequestration outcomes. The feasibility and leakage risks of this method were evaluated on a 100,000-year timescale. Results indicate that the injection of cold seawater significantly improves the pressure–temperature conditions of subsea sediments, facilitating early hydrate formation and markedly increasing the initial CO2 hydrate formation rate. Consequently, the distribution pattern of hydrate saturation changes, forming a double-layer hydrate shell. Over the long term, while cold seawater injection does not significantly reduce CO2 leakage, it does increase the safety margin between the hydrate layer and the seabed, enhancing the safety coefficient for long-term CO2 hydrate sequestration. Through detailed analysis of the behavior of CO2 components during sequestration, this study provides new theoretical insights into subsea CO2 hydrate storage. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coal and gas outburst is one of the most serious kinetic disasters in coal mines, and the use of gas hydrate curing technology to reduce the gas pressure and its gradient in the coal body can reduce the probability of coal and gas outburst accidents. In order to investigate the influence of driving force on the growth kinetics of CH4 hydrate in coal medium, the experimental study on the growth kinetics of gas hydrate in coal medium under three driving force conditions was carried out by using the experimental system of gas hydrate growth kinetics, and the influence of the driving force on the parameters such as gas consumption and growth rate during the synthesis process of gas hydrate in coal medium was discussed. The results show that: within the same particle size range, the nucleation time of hydrate in each particle size range does not completely follow the law of subsequent shortening when the driving force is increased, and the nucleation of CH4 hydrate in coal medium has a certain degree of randomness; the phenomenon of multiple nucleation occurs in the synthesis process; the gas consumption of CH4 hydrate in the coal medium increases with the increase of the driving force; the growth rate of gas hydrate in coal medium is increased with the increase of the driving force, and the growth rate of gas hydrate in coal medium is improved with the increase of driving force under the condition of unchanged temperature and particle size. The effect of driving force on the average growth rate at the early stage of synthesis is more significant.

Lopinavir is a potent protease inhibitor that is used as a first-line pharmaceutical drug for the treatment of HIV. The multi-component solvated Lopinavir crystal, systematic name (2S)-N-[(2S,4S,5S)-5-[2-(2,6-dimethylphenoxy)acetamido]-4-hydroxy-1,6-diphenylhexan-2-yl]-3-methyl-2-(2-oxo-1,3-diazinan-1-yl)butanamide–ethane-1,2-diol–water (8/3/7) 8C37H48N4O5·3C2H6O2·7H2O, was prepared using evaporative methods. The crystalline material obtained from this experimental synthesis was characterized and elucidated by single-crystal X-ray diffraction (SC-XRD). The crystal structure is unusual in that the unit cell contains 18 molecules. The stoichiometric ratio of this crystal is eight Lopinavir molecules [8(C37H48N4O5)], three ethane-1,2-diol molecules [3(C2H6O2)] and seven water molecules [7(H2O)]. The crystal packing features both bi- and trifurcated hydrogen bonds between atoms.

Gas separation is a critical application of gas hydrates, and accurately predicting separation performance is crucial. In this study, we used thermodynamic calculations to predict the equilibrium phase of gas hydrates for various mole fractions of CO2 + CH4 gas mixtures. We also determined the mole fraction of each gas component trapped within the hydrate clathrate. To predict the equilibrium points, we used the Soave–Redlich–Kwong（(SRK) equation of state for the gas phase, the nonrandom two-liquid (NRTL)model for the liquid phase, and the Chen–Guo model for the hydrate phase. We modified the hydrate fugacity formula and introduced a new function to improve the accuracy of the Chen–Guo model. By incorporating experimental equilibrium results from our study and another study, we developed a correlation based on gas mixture composition and temperature, resulting in highly accurate predictions. The use of this new correlation for hydrate fugacity calculation significantly improved precision, as evidenced by an average absolute deviation percent of calculated pressures (AADP) of 1.34% for pure CO2 and 1.25% for CH4. When considering the 27 data points of different CO2 + CH4 mixtures, the AADP% was 1.98%.To implement the model to predict equilibrium phases, we used the Chen–Guo framework to determine the mole fraction of each gas component in the hydrate mixture. Interestingly, we discovered a linear correlation between the CO2 mole fraction in the hydrate and equilibrium pressure, with a slope of approximately 0.001 and a y-intercept of less than one, for all gas compositions. Therefore, we can conclude that low thermodynamic conditions (temperature and pressure) result in a high CO2 mole fraction in the hydrate phase and great separation efficiency.

Prevention of hydrate plugs during oil and natural gas transportation in the pipeline network is challenging and may require significant operating expenditure. Synthetic inhibitors are deployed in large volumes to inhibit hydrate formation, and these inhibitors are highly expensive and toxic to the environment. Consequently, this study investigates the effectiveness of cassava (Manihot esculenta) leaf extract as an environmentally friendly, biodegradable, and cost-efficient novel green inhibitor of gas hydrate. Cassava is a tropical plant cultivated majorly in Nigeria, and its leaf is, in almost all cases, discarded as waste. In this study, an extract is made from cassava leaf and used in varying weight percentages as hydrate inhibitors using a locally fabricated mini flow. Results show cassava leaf extract (CLE) performed significantly better than conventional inhibitor methanol (MeOH) at a higher weight percentage. The presented results show that at varying weights of 0.02 wt%, 0.04 wt%, and 0.06 wt% of the CLE, the final pressures were found to be the pressures were found to be 29 psi, 27 psi, and 24 psi, respectively. These pressures indicates that more gas was converted to hydrate with the lower pressure value in the system. These results were compared with 2 wt%, 4 wt%, and 6 wt% of MeOH, with a differential pressure of 28 psi, 46 psi, and 50 psi, respectively. CLE's gas hydrate inhibition capacity was found at pressure conditions of 51.7 psi, 55 psi, and 60 psi for 0.02 wt%, 0.04 wt%, and 0.06 wt%, respectively. These results demonstrate that CLE performed significantly better than methanol as a gas hydrate inhibitor, despite being used in a much lower dosage than methanol, which had inhibition pressures conditions of 53.3 psi, 23.3 psi, and 16.7 psi for 2 wt%, 4 wt%, and 6 wt%, respectively. [ABSTRACT FROM AUTHOR]

Ruxolitinib {RUX; systematic name: (3R)‐3‐cyclopentyl‐3‐[4‐(7H‐pyrrolo[2,3‐d]pyrimidin‐4‐yl)‐1H‐pyrazol‐1‐yl]propanenitrile, C17H18N6} is an orally bioavailable JAK1/2 inhibitor approved for treating intermediate‐ or high‐risk myelofibrosis (MF) and high‐risk polycythemia vera (PV). Recent patents claim that RUX can exist in many different forms, information for which is important for the clinical utilization of RUX, especially for the formulation and bioavailability of the drug. But there has been no detailed study on its forms so far. Herein crystals of RUX and its dihydrate (RUX‐2H; C17H18N6·2H2O) and phosphate (RUX‐P; systematic name: 4‐{1‐[(1R)‐2‐cyano‐1‐cyclopentylethyl]‐1H‐pyrazol‐4‐yl}‐7H‐pyrrolo[2,3‐d]pyrimidin‐3‐ium dihydrogen phosphate, C17H19N6+·H2PO4−) were prepared successfully and their structures studied in detail for the first time. Our study shows that the three crystals of RUX differ in the orientation of the pyrimidine ring relative to the pyrazole ring of the RUX molecule, and in their hydrogen‐bond interactions. The water molecules in RUX‐2H and the dihydrogen phosphate anion in RUX‐P enrich the hydrogen‐bond networks in these forms. The expected proton transfer occurs in RUX phosphate and the protonated N atom is engaged in a charge‐assisted hydrogen bond with the counter‐anion. Hydrogen‐bonding interactions dominate in the crystal packing of the three forms. The detailed conformations and packing of the three forms were compared through the calculation of both Hirshfeld surfaces and fingerprint plots. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Natural gas hydrate is a kind of low-carbon and clean new energy, so research on its efficient extraction in terms of theory and technology is particularly important. Combined thermal injection and depressurization is an effective method for extracting natural gas hydrate. In this study, the classical local heat equilibrium model was modified, and a pore-scale fully coupled unsteady heat transfer model for hydrate reservoirs was set up by considering multiple forms of heat flow accompanying hydrate's decomposition and gas–liquid flow. Based on this model and the basic geological information of the X2 hydrate reservoir in the western Pacific Ocean, a numerical model of gas hydrate extraction using combined heat injection and depressurization was constructed to simulate the production performance of the hydrate reservoir. The results were fully compared with the results obtained by the depressurization method alone. The results indicated the hydrate extraction via a combined heat injection and depressurization would have a cumulative gas production of 31.609 million m3 and a cumulative water production of 1.5219 million m3, which are 72.57% higher and 31.75% lower than those obtained by depressurization alone, respectively. These study results can provide theoretical support for the industrial extraction of gas hydrate in seas. [ABSTRACT FROM AUTHOR]

Polymorphic control is vital for the quality control of pharmaceutical crystals. Here, we investigated the relationship between the hydrate and anhydrate polymorphs of a monoacylglycerol acyltransferase 2 inhibitor (S-309309). Solvent evaporation and slurry conversion revealed two polymorphs, the hydrate and the solvate. The solvate was transformed into the hydrate by heating. X-ray powder diffraction demonstrated that the hydrate was transformed into an anhydrate via an intermediate state when heated. These crystal forms were confirmed under controlled humidity conditions; the presence of the anhydrate, the intermediate hydrate, or the hydrate depended on the relative humidity at 25 °C. The stoichiometry of S-309309 in water in the hydrate form was 4:1. The hydrates and anhydrates exhibited similar crystal structures and stability. The water of hydration in the intermediate hydrate was 0.1–0.15 mol according to the dynamic vapor sorption profile. The stability and dissolution profile of the anhydrate and hydrate showed no significant change due to similar crystal lattices and quick rehydration of the anhydrate. A mechanism for the reversible crystal transformation between the anhydrate and pseudo-polymorphs of the hydrate was discovered. We concluded that S-309309 causes a pseudo-polymorphic transformation; however, this is not a critical issue for pharmaceutical use. [ABSTRACT FROM AUTHOR]

The term "desolvation inability" is proposed in order to describe the alteration of the original chemical structure of a solute ("decomposition") prior to the solvent's full removal upon the heating of the solvate. This behavior has been sporadically reported; however, it is much more frequent, and it is the basis of various, seemingly unrelated, effects/processes, e.g., the vinegar syndrome of cellulose acetate cinematographic films, in thermal energy storage. An explanation and a criterion/index for the prediction of this behavior are provided based on the comparison of the Gibbs free energies of decomposition and desolvation. A new approach for the expression of the Gibbs free energy of desolvation is proposed by reversing the roles of the solute and solvent and by regarding water as the solute rather than as the solvent, while the solute is treated as a solid solvent. This approach results in lower solvation/desolvation Gibbs free energy values. Based on the above, the experimentally observed thermal behavior of three inorganic hydrates is predicted and explained. Theoretically and experimentally, it is supported that decomposition is possible at sub-zero (°C) temperatures and the regarded simultaneous drying and protection of heat-sensitive substances by freeze-drying, at least in some cases, e.g., for the case of gallic acid, is an unverified myth. [ABSTRACT FROM AUTHOR]

Objective The gas flow during the exploitation of sour gas fields often contains sour components such as carbon dioxide (CO2 ) and hydrogen sulfide (H2S), which are easy to form natural gas hydrates (hydrate for short) and cause pipeline blockages. The aim is to solve the problem of unclear mechanisms of sour component absorbers on hydrates, which could provide a theoretical for removing sour gas components and preventing hydrate formation. Methods In this paper, the isothermal and isochoric methods investigated the effects of the mass fraction, stirring state, and initial pressure of N-methyldiethanolamine (MDEA) solution on the absorption law of CO2 . The effects of MDEA solution on the growth rate and macroscopic morphology of CO2 hydrate were also studied and compared to the conventional thermodynamic inhibitor ethylene glycol (EG). Results The study indicated that the absorption rate of CO2 showed a trend of increasing and then decreasing with the increase of the mass fraction of the MDEA solution. The stirring state and lower initial pressure could accelerate the absorption rate of CO2 and increase the amount of gas absorption. At the gas-liquid interface, hydrate crystals grew in a two-dimensional mode, and MDEA could change the macroscopic morphology of CO2 hydrates. Increasing the mass fraction of MDEA solution could significantly increase the time for CO2 hydrates to cover the surface of the solution and reduce the growth rate of CO2 hydrates. In contrast to the EG, the kinetic inhibition of MDEA hydrates was poorer, but the cover time of the hydrates film was longer, and the growth rate was slower. Conclusions It is analyzed that MDEA could form hydrogen bonds with water molecules in the solution and compete with hydrates for water molecules, reducing water activity. It could also combine with CO2, and compete with hydrates, significantly decreasing the growth rate of hydrate. The research results have theoretical significance for the guidance of the separation and capture of sour gases and natural gas transportation. [ABSTRACT FROM AUTHOR]

Objective CO2 storage via the hydrate method is one of the potential carbon storage methods because of its stability and high gas storage capacity. The use of formation conditions in permafrost region has more unique advantages. CO2 is injected into the permafrost region, and solid-state CO2 hydrate is formed under specific temperature and pressure conditions to achieve long-term stable storage. Methods According to the temperature and pressure conditions of the formation in the permafrost region of China, the temperature (1.27 °C and 2.72 °C) and effective pore water content (40%) corresponding to different formation depths (150 m and 200 m) and different initial injection pressures (3.5 MPa, 4.5 MPa and 5.5 MPa) were selected. The characteristics of kinetic parameters such as temperature and pressure changes, storage rate, final water conversion rate and final storage ratio in the CO2 storage process via the hydrate method were analyzed. Results The results of the CO2 hydrate storage process under different initial injection pressures show that the higher the initial injection pressure, the shorter the induction time required for hydrate storage and the larger the pressure drop. Higher injection pressure results in a slower storage rate at the initial stage and a reduced duration of the slow storage period. The higher the injection pressure, the higher the hydrate storage ratio, the final water conversion rate, and the hydrate phase saturation at the end of the reaction. The higher the storage temperature, the more obvious the effect of pressure on the gas storage ratio. Conclusions The best CO2 storage effect was achieved under 40% water content at the depth of 150 m (the average temperature of the formation is 1.27 ℃) and 5.5 MPa. [ABSTRACT FROM AUTHOR]

Since hydrate resources play a part of the stratigraphic framework structure in sediments, establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day. Among the proposed methods, the spontaneous displacement of CH4 from hydrate cages by CO2 seems to be a perfect mechanism to address gas production and CO2 storage, especially in today's strong demand for carbon reduction and replacing clean energy. After extensive lab researches, in the past decade, injecting a mixture of CO2 and small molecule gas has become a key means to enhance displacement efficiency and has great potential for application. However, there is a lack of in-depth research on gas flow in the reservoir, while the injected gas always passes through low-saturated hydrate areas with high permeability and then occurs gas channel in a short term, finally resulting in the decreases in gas production efficiency and produced gas quality. Therefore, we explored a new injection-production mode of alternate injection of N2 and CO2 in order to fully coordinate the advantages of N2 in enhanced hydrate decomposition and CO2 in solid storage and heat compensation. These alternate "taking" and "storing" processes perfectly repair the problem of the gas channel, achieving self-regulation effect of CH4 recovery and CO2 storage. The 3-D experimental results show that compared to the mixed gas injection, CH4 recovery is increased by >50% and CO2 storage is increased by >70%. Additionally, this alternate injection mode presented a better performance in CH4 concentration of produced gas and showed outstanding N2 utilization efficiency. Further, we analyzed its self-adaptive gas flow mechanism and proposed an application model of "one injection and multiple production". We look forward to this study accelerating the application of CO2-CH4 replacement technology. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Since hydrate resources play a part of the stratigraphic framework structure in sediments, establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day. Among the proposed methods, the spontaneous displacement of CH4 from hydrate cages by CO2 seems to be a perfect mechanism to address gas production and CO2 storage, especially in today's strong demand for carbon reduction and replacing clean energy. After extensive lab researches, in the past decade, injecting a mixture of CO2 and small molecule gas has become a key means to enhance displacement efficiency and has great potential for application. However, there is a lack of in-depth research on gas flow in the reservoir, while the injected gas always passes through low-saturated hydrate areas with high permeability and then occurs gas channel in a short term, finally resulting in the decreases in gas production efficiency and produced gas quality. Therefore, we explored a new injection-production mode of alternate injection of N2 and CO2 in order to fully coordinate the advantages of N2 in enhanced hydrate decomposition and CO2 in solid storage and heat compensation. These alternate "taking" and "storing" processes perfectly repair the problem of the gas channel, achieving self-regulation effect of CH4 recovery and CO2 storage. The 3-D experimental results show that compared to the mixed gas injection, CH4 recovery is increased by >50% and CO2 storage is increased by >70%. Additionally, this alternate injection mode presented a better performance in CH4 concentration of produced gas and showed outstanding N2 utilization efficiency. Further, we analyzed its self-adaptive gas flow mechanism and proposed an application model of "one injection and multiple production". We look forward to this study accelerating the application of CO2-CH4 replacement technology. [ABSTRACT FROM AUTHOR]

At present, the problem of global warming is becoming increasingly serious, and one of the main culprits is the increasing amount of carbon dioxide emissions. Although the traditional carbon capture technologies can reduce the concentration of CO2 in the atmosphere, it has a series of problems such as high energy consumption, high cost, low efficiency or unfriendly environment. Hydrate-based carbon dioxide separation are considered to be a technology with great application and development prospects. Compared with the traditional method of carbon dioxide separation, the hydrate method has the advantages of simple process, low energy consumption and environmental friendliness. This review introduces the advantages of hydrate method compared with traditional carbon capture technologies, expounds the theory of carbon dioxide capture by hydrate, and the strengthening and improvement techniques of hydrate method, including thermodynamic promoter, kinetic promoter and mechanical reinforcement, and introduces the practical application of hydrate method in various fields.

The formation and deposition of hydrates downstream the wellhead restrict flow and constitute a major flow assurance problem that affects the safe gas production and transportation. Many works have been done to predict the downstream hydrate formation temperature howbeit, considers only the pressure and the specific gravity of the gas. In this study, in addition to pressure and the specific gravity of the gas, the acid gas compositions was integrated to develop a non-linear empirical model for predicting the onset of hydrate formation temperature through the combination of logarithmic and polynomial functions. The results show good agreement with existing models particularly those that incorporates specific gravity and pressure as the independent variables which are either logarithmic or polynomial models. In fact, at some pressures, it performed better than the existing model with which it was compared. When compared with the observed data, the model has a coefficient of correlation (R²) of 0.95 and a percentage average absolute deviation (%AAD) of 2.19% as against the other models which have 15.402%, 15.426% and 74.4166% AAD respectively. The developed model has both logarithmic function and polynomial function integrated, hence the lowest %AAD and good prediction capability compared to other models. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The formation of hydrate flow barriers has become one of the most severe flow assurance issues in deepwater gas well testing and production processes. On the basis of analyzing the temperature distribution of the external environment of deep-water gas wells, this study explores the influence of downhole throttling on the distribution of hydrate generation areas in the wellbore under downhole throttling conditions. According to the research results: The external environmental temperature of the deep-water wellbore shows a trend of first decreasing and then increasing from the surface to the reservoir, and the water temperature at the mud line is the lowest point along the way; The water temperature in the mixed layer and thermocline layer within 200m of the upper part of seawater is greatly influenced by surface temperature and season, while the temperature in the constant temperature layer is low and has little variation; The temperature increases approximately linearly from the mud line to the reservoir, reaching the highest value after reaching the reservoir; As the testing gas volume increases, the wellbore flow temperature curve shifts to the right. Due to the increase in heat carrying capacity under high gas production, it is less affected by the external low-temperature environment and the temperature curve becomes smoother; The region of hydrate formation and subcooling distribution after throttling are determined by the decrease in fluid flow temperature and hydrate phase equilibrium temperature affected by the Joule Thomson effect; Low depth throttling often leads to a temperature drop of the fluid greater than the equilibrium temperature drop of the hydrate phase, promoting the expansion of the hydrate generation area and an increase in undercooling, exacerbating the risk of hydrate blockage; Reasonable high depth throttling can effectively avoid the conditions for hydrate formation and play a role in hydrate prevention. [ABSTRACT FROM AUTHOR]

Multi-gradient drilling is a new offshore drilling method. The accurate calculation of the related wellbore temperature is of great significance for the prediction of the gas hydrate formation area and the precise control of the wellbore pressure. In this study, a new heat transfer model is proposed by which the variable mass flow is properly taken into account. Using this model, the effects of the main factors influencing the wellbore temperature are analyzed. The results indicate that at the position where the separation injection device is installed, the temperature increase of the fluid in the drill pipe is mitigated due to the inflow/outflow of hollow spheres, and the temperature drop of the fluid in the annulus also decreases. In addition, a lower separation efficiency of the device, a shallower installation depth and a smaller circulating displacement tend to increase the temperature near the bottom of the annulus, thereby helping to reduce the hydrate generation area and playing a positive role in the prevention and control of hydrates in deepwater drilling. [ABSTRACT FROM AUTHOR]

Methane hydrate formation is analytically studied in the presence of the water memory effect using the classical nucleation theory. The memory effect is introduced as a change in nucleation site from a three-dimensional heterogenous nucleation on a solid surface with cap-shaped hydrate clusters (3D-HEN) to a two-dimensional nucleation on the solid hydrate residue surface with monolayer disk-shaped hydrate clusters (2D-NOH). The analysis on the stationary nucleation of methane hydrate under isobaric conditions shows that the memory effect caused an average decrease of 4.4 K in metastable zone width, or subcooling. This decrease can be erased at higher dissociation temperatures (ΔT > 17.2 K) due to a decrease in the concentration of 2D-NOH nucleation sites. Moreover, the probability of hydrate formation is estimated for the purpose of quantifying risk associated with methane hydrate formation in the presence of the memory effect. [ABSTRACT FROM AUTHOR]

Stability and potency improvement have been reported by reacting levofloxacin (LF) with citric acid (CA) in a (1:1) molar ratio. However, CA is known to be irritant to the gastrointestinal tract and should be minimized. In a novel approach, this experiment aimed to prepare LF – CA salt with reduced CA, the (2:1) molar ratio, study the structure, and investigate its solubility, stability, and potency improvement. Solvent-dropped grinding and slow evaporation methods were used to prepare the new ratio composition salt, characterized by electrothermal, differential scanning calorimetry, and powder X-ray diffractometry to confirm the physically new solid-state formation. Next, Fourier transform spectrophotometry identified the chemical interaction between LF and CA. After that, a comprehensive structural study using single-crystal X-ray diffractometry determined the 3D structure of the new salt, which determined the solid physicochemical behavior. Finally, stability, solubility, and potency tests were done to investigate the benefits of the new LF-CA composition. As a result, this experiment successfully synthesized the salt, which bound 4.5 water molecules, named LFCA (2:1) - 4.5 hydrate. This new solid-state salt was comparable with the established (1:1) molar ratio in solubility, stability, and potency, higher than LF alone. Hereafter, with a reduced CA portion, this new composition holds potential for further development in drug formulation as a stable, safer, and more efficient antibiotic.

An explainable supervised machine learning was used to inspect the insight into the former selection for methane hydrate forming systems in the presence of water-soluble organic molecules. The former is an important ingredient that allows methane hydrate formation at conditions closer to the ambient in solidified natural gas technology (SNG). Over 800 samples were collected from literatures and experiments and utilized for supervised modeling. The data were split into train and test sets with an 80:20 ratio, preprocessed, and used to build predictive models, which are linear regression-based and tree-based models. Categorical Boosting Machine Regressor (CatBoost) performed the best on the equilibrium temperature prediction using 10 relevant attributes on the unseen data set with R2 of 0.973, RMSE of 1.375, and MAPE of 0.269 %. Feature selection suggested that only 7 necessary attributes are adequate to make a model, which is comparable to the full model. The model was then explained via Shapley Additive Explanations (SHAP) analyses. Cyclic molecules without hydrogen bond donors, with low polarity, at a mole fraction in the range of 0.02 – 0.07 were suggested to be effective formers that can shift the equilibrium temperature to higher levels.

This study investigates the natural gas hydrates within the Qiongdongnan Basin by integrating well-log and seismic data. Through pre-stack inversion and rock physics analysis, key parameters such as P-wave and S-wave impedances were utilized to distinguish hydrate-bearing formations from other geological bodies. A low-frequency model was constructed using the Inverse Distance Weighting (IDW) algorithm to improve the precision of parameter inversion. This study employs a multi-constraint inversion strategy, incorporating hard constraints from multiple wells and soft constraints from geological frameworks, ensuring reliable inversion results. Findings indicate that hydrate reservoirs are characterized by increased wave velocity and density due to hydrate accumulation, providing insights into the spatial distribution and characteristics of hydrates. This research enhances the understanding of hydrate reservoirs and offers valuable data for exploration in the Qiongdongnan Basin.

The interaction of fullerenes and their derivatives with environmental molecules such as oxygen or water was crucial for the rational design of low-dimensional materials and devices. In this paper, the near-edge X-ray absorption fine structure (NEXAFS), X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) shake-up satellites were employed to distinguish the oxides and hydrates of the fullerene C60 and azafullerene C59N families. The study includes various isomers, such as the open [5,6] and closed [6,6] isomers of C60O, C60H(OH), C60-O-C60, C60H-O-C60H, C59N(OH) and C59N-O-C59N, based on density functional theory. These soft X-ray spectra offered comprehensive insights into the molecular orbitals of these azafullerene molecular groups. The oxygen K-edge NEXAFS, carbon and oxygen K-edge XPS shake-up satellite spectra provided valuable tools for distinguishing oxides or hydrates of fullerene C60 and azafullerene C59N. Our findings could significantly benefit the development of fullerene functional molecular materials and expand the application scope of soft X-ray spectroscopy as a molecular fingerprinting tool for the fullerene family. [ABSTRACT FROM AUTHOR]

Understanding the hydrate adhesion is important to tackling hydrate accretion in petro-pipelines. Herein, the relationship between the Tetrahydrofuran (THF) hydrate adhesion strength (AS) and surface stiffness on elastic coatings is systemically examined by experimental shear force measurements and theoretical methods. The mechanical factor-elastic modulus of the coatings greatly dictates the hydrate AS, which is explained by the adhesion mechanics theory, beyond the usual factors such as wettability and structural roughness. Moreover, the hydrate AS increases with reducing the thickness of the elastic coatings, resulted from the decrease of the apparent surface elastic modulus. The effect of critical thickness for the elastic materials with variable elastic modulus on the hydrate AS is also revealed. This study provides deep perspectives on the regulation of the hydrate AS by the elastic modulus of elastic materials, which is of significance to design anti-hydrate surfaces for mitigation of hydrate accretion in petro-pipelines. [ABSTRACT FROM AUTHOR]

Copyright of Energy Chemical Industry is the property of Energy Chemical Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Telmisartan is an anti-hypertensive drug that exhibits poor aqueous solubility. In this work, salt formation was utilized to address this issue. Three hydrochloride salts of telmisartan (TELHCl), a trihemihydrate hydrochloride salt (TELHCl-Hyd), and two anhydrate forms (TELHCl-A and TELHCl-B) were obtained. The crystal structures of TELHCl-Hyd and TELHCl-A were determined using single-crystal structure analysis. TELHCl-Hyd is a channel hydrate that has structural similarities with TELHCl-A. The structures of both crystals are mainly composed of chain structures formed by centrosymmetric dimers connected via carboxylic–benzimidazole hydrogen bonding. Despite their structural similarities, the dehydration of TELHCl-Hyd led to the formation of TELHCl-B. The solubility, intrinsic dissolution rate (IDR), powder flowability, and tabletability of TELHCl-Hyd and TELHCl-B were characterized and compared with those of the telmisartan free base form (TEL). The hydrochloride salts enhanced the solubility of telmisartan approximately 10 to 20 times and maintained the spring parachute effect up to 24 h. The IDR was also improved due to the existence of a hydrophilic channel that facilitates the dissolution of telmisartan cations. The resulting salts had a larger particle size and a more favorable crystal morphology that led to a better powder flowability. However, the tabletability was not improved by salt formation. The TEL exhibited a defined slip plane and a higher specific surface area that may assist the tableting process. [ABSTRACT FROM AUTHOR]

The formation and decomposition process of natural gas hydrate (NGH) involves many disciplines and theories. Comprehensively evaluating the mechanical and physical properties of hydrate-bearing sediments (HBS) and clarifying the influence law of hydrate decomposition on reservoir structure. It is of great significance to realize the safe exploitation of NGH. At present, the test research on HBS shows the characteristics of diversification, multi-scale and multi-discipline. In order to enhance the comparison of test conclusions and promote the correlation of science and technology. In this study, based on different experimental test methods, the existing test methods are categorized into two types: direct test methods and indirect test methods. By summarizing and analyzing the triaxial test and direct shear test of hydrates, the commonalities and differences of different types of hydrates are pointed out. Meanwhile, the mechanical behavior of hydrate under different influencing factors is reviewed in particular to guide practical works. Then, by combing the visualization techniques of hydrate laboratory tests. The applications of X-ray computed tomography (X-CT) and nuclear magnetic resonance (NMR) in microstructure, pore space, and morphology observation are emphasized. Additionally, an overview of the acoustic and electrical characterization of hydrates in geophysical methods is presented. The correlation of acoustic wave detection and resistivity test with hydrate distribution morphology and saturation estimation is discussed. Finally, the problems existing in the current HBS experimental research are analyzed and targeted suggestions are given. The future development trend of HBS experimental research is discussed, with a view to providing ideas and references for HBS experimental research. • Mechanical and physical properties of HBS are analyzed. • The results of triaxial test and direct shear test on HBS are summarized. • The visualization method of HBS are introduced. • The application of geophysical methods to hydrate research is illustrated. • The current status and challenges of experimental hydrate research are outlined. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding the mechanisms governing hydrate formation and the flow characteristics of slurry in oil-water systems is crucial for developing effective hydrate risk management strategies and ensuring safe pipeline operations. This paper provides an overview of experimental devices used to study hydrate behavior in oil-water systems. It describes the structural composition, notable features, and application scenarios of both macroscopic and microscopic devices commonly employed in hydrate research. A comparative analysis of the advantages, disadvantages, and application results of each device is conducted with respect to hydrate nucleation, growth and decomposition rates, particle aggregation evaluation, rheological properties of slurry, and the development of quantitative models. The paper also considers the current research landscape to provide suggestions for future investigations of hydrates in oil-water systems. It anticipates that future studies will involve multi-scale approaches, coupling spectroscopic instruments with existing devices, and exploring the interfacial properties of water hydrate particles under high-pressure conditions. Furthermore, the paper envisions the development of a risk assessment method for hydrate blockage based on parameters such as hydrate growth rate, aggregation characteristics, and slurry mobility.