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The world’s first offshore methane hydrate extraction was conducted in 2013 at the Daini-Atsumi Knoll located in the eastern Nankai Trough. The results indicated that the gas production rate of a single vertical well cannot meet the requirement for commercialisation of methane hydrate production. Therefore, a trial multi-well system has been considered for future hydrate production. Understanding the ‘influence distance’ of extraction wells within methane hydrate turbidite reservoir formations, such as that of the Nankai Trough, is significant to the design of the proposed multi-well system. In this study, the boundary effects are examined for cases involving different values of permeability and initial hydrate saturation for the modelled turbidite formations. A relationship is proposed to predict the longest simulation time for a given set of lengths and parameters. The two concepts of critical production time (CPT) and turbidity/homogeneity coefficient ratio (THCR) are introduced to analyse the interaction between the effects of model size and heterogeneities. It is found that the CPT can be normalised by the radius of the model; the THCR is affected by the relative thickness of the sand and clay layers.

The hydrate morphology in sandy methane hydrate (MH)-bearing sediment (MHBS) is commonly classified as pore-filling, cementation, grain-coating and load-bearing. This paper presents a numerical investigation into the mechanical behaviour of coexistence-type MHBS using the discrete-element method (DEM). The coexistence type is represented as a combination of pore-filling and cementation types. For MHBS with a given MH saturation (S MH), the relative content of pore-filling and cementation is characterised by the cement ratio λ (λ = 0 means pure pore-filling and λ = 1 means pure cementation). A series of drained triaxial compression tests is simulated, and micromechanical variables such as bond breakage are examined. The results show that (a) the strength and dilatancy of the coexistence-type MHBS are higher when the cement ratio is larger. The normalised strength and secant modulus increase linearly with the cement ratio. (b) When the cement ratio increases, the critical-state line on the mineral void ratio e cr–ln p′ projection shifts towards a higher position and the bond breakage ratio is larger. (c) The shear stress of the coexistence-type MHBS with cementation is affected by the MH generation process due to the MH bond breakages.

Gas hydrates are regarded as one of the most promising alternative sources of energy, which have the potential to address the energy demand of a contemporary society. Based on the field explorations in the Eastern Nankai Trough (Japan), a multilayered hydrate reservoir model has been conceptualised and its behaviours during depressurisation production are simulated. This model incorporates the effects of the initial reservoir temperature and permeability on the mechanism of hydrate dissociation, which in turn affects the gas production. It is shown that the dissociation process is largely affected by the initial temperature distribution within the reservoir layers, and the ‘warmer’ reservoirs show (consistently) higher production potential. Furthermore, the gas production could be improved significantly, by increasing the permeability of the wellbore region, which can be achieved through the fracturing process. The close match between the simulation results and the field tests is noteworthy. The proposed multilayered model would be quite useful for analysing the efficacy of the ‘production strategy’, in most real-life situations.

In this study, Ti6Al7Nb titanium alloy has been subjected to micro-arc oxidation (MAO) process and hydrothermal (HT) treatment sequentially. MAO process was conducted in calcium acetate hydrate (Ca(CH3COO)2.H2O) and disodium hydrogen phosphate anhydrous (Na2HPO4) containing reference electrolyte with and without the addition of silver acetate (AgC2H3O2) to provide antibacterial efficiency along with good bioactivity. Subsequently, HT treatment was employed to MAO’ed samples in an alkaline solution (pH = 11) at 230°C. HT treatment induced the covering of the titanium oxide (TiO2)-based MAO coatings with 1–2 µm thick exterior layer composed of nano-rods of titanium oxide and hexagonal columns of hydroxyapatite (HA). The presence of silver (Ag) in the MAO coating refined the structure of the HT treatment-induced exterior layer. As the primary indication of enhancement of the bioactivity, HT treatment accelerated apatite formation in the SBF solution irrespective of the silver presence, which delayed the apatite formation on the untreated MAO coatings. Moreover, HT treatment reduced the release of silver from the coatings into the SBF solution.

Acoustic properties play an important role in the identification of natural gas hydrate resources, the estimation of their potential yield and the evaluation of soil stabilisation during exploration. Physical properties, such as hydrate saturation, porosity and clay content, are dominant factors that affect the acoustic properties of sediments. When considering these properties, the modified Biot–Gassmann theory of Lee (BGTL), the effective-medium theory (EMT) and the Frenkel–Gassmann equation (FG) are adopted to show the characteristics of compressional and shear wave velocities due to variation of the physical properties of different sediments. The results show that hydrate saturation has the highest sensitivity in the three models, followed by the porosity and clay content. To evaluate the applicability of different models, the data from two case studies are compared – actual survey data from the site995 stations and 2L-38 logging. The results indicate that the BGTL and EMT models are more suitable for hydrate-bearing sediments with a hydrate saturation less than 10%, a clay content of 50–70% and a porosity of 60–70%, while the FG model is more suitable for hydrate-bearing sediments with a hydrate saturation of 30–70%, a clay content of 30–60% and a porosity of 30–50%.

Natural gas hydrate (NGH) holds great promise as a source of clean energy. It is critical for acquiring the largest possible in situ NGH core for NGH eigen features and resource assessment. However, the existing NGH coring technology has limitations, such as temperature increments, limited coring diameters, low coring rates, and complex coring structures. Therefore, this study designs and proposes an NGH freezing coring (NGHFC) method and verifies the freezing and coring capacities of the NGHFC method in laboratories and experimental wells. Results suggest that NGHFC shows good freezing and heat-retention properties. A freezing core heat transfer model is developed. According to the actual air temperature and operating time, the optimum initial temperature of the cold source can be determined using this model. The average coring rate of NGHFC can reach 77.86 %. The research results will provide a new idea of coring gas hydrates.

Methane hydrate has become one promising energy resource for humankind. In this study, recent worldwide onshore/offshore drilling and production activities are analysed. The most recent reports from sites such as Japan (2013 and 2017) and China (2017) show that the road towards comprehensive utilisation of methane hydrate is underway. Though the production methods (depressurisation, thermal stimulation and carbon dioxide (CO2) replacement) diverge in safety and efficiency, potential has been confirmed for future large-scale utilisation. The world hydrate policy is dependent on the socioeconomic status and environmental concerns in major countries. It is urged that international regulations on commercial explorations be settled for methane hydrate projects.

In this work, experiments and comprehensive insights into the proposed covering liquid method to intensify self-preservation effect for methane (CH4) storage are presented. The CH4 hydrate decomposition percentage was 17.6% with the pressure of 0.61 MPa after 12 h at 266.0 K without a covering liquid, which can be reduced to 12.4%, 13.8%, 13.0%, and 8.3% with the pressure of 0.26 MPa, 0.33 MPa, 0.51 MPa, and 0.37 MPa by covering with tetrahydrofuran (THF), cyclopentane (CP), cyclohexane, and n-tetradecane, respectively. When the temperature for CH4 hydrate decomposition was 274.2 K, covering with THF, CP, cyclohexane, and n-tetradecane failed to inhibit CH4 hydrate decomposition. The results suggested that the covering liquid may form a new solid layer (a hydrate layer or other solidified layer) around the CH4 hydrate, which inhibit CH4 transfer below the freezing point of water. However, the new solid layer cannot resist the fast transfer of CH4 from decomposed CH4 hydrate above the freezing point of water. The same phenomenon was also observed in a sodium dodecyl sulfonate (SDS)-dry solution CH4 hydrate formation system. Therefore, the covering method can only intensify the self-preservation effect below the freezing point of water, but cannot generate a self-preservation effect.

In marine continental margins, high saturations of natural gas hydrate are observed within the gas hydrate stability zone, but the gas migration pathways to the hydrate reservoir are not often clear. We focus on a site in Green Canyon Block 955 (GC 955) in the Gulf of Mexico, where gas hydrate occurs in a 35 m-thick reservoir with saturations of 79-93% in numerous centimeter- to decimeter-thick sandy silt layers and little to no gas hydrate in the interbedded cm to decimeter-thick clayey silt layers. Different datasets (well logging, coring, and seismic data) suggest different types of potential methane migration mechanisms. For example, relatively high particulate organic carbon content in the reservoir and the microbial methane source indicated by gas chromatography and methane isotopes suggest gas might be made locally and migration could occur through dissolved methane sources or water advection. In contrast, the visible deeply rooted faults intersecting the gas hydrate reservoir and the gas pockets adjacent to the faults on seismic data suggest that free gas may migrate directly into the reservoir. We tested three different mechanisms to form gas hydrate at GC 955: short-range methane diffusion, short-range methane diffusion coupled with upward water advection, and free gas flow. The 1-D and 2-D numerical models show that both the short-range migration and the upward water advection are not enough to form high saturations gas hydrate at GC 955, and that free gas flow is required to form the high saturations of gas hydrate observed at GC 955.

Natural gas hydrates can readily form in deep-water oil production processes and pose a great threat to the oil industry. Moreover, the coexistence of hydrate and asphaltene can result in more severe challenges to subsea flow assurance. In order to study the effects of asphaltene on hydrate growth at the oil–water interface, a series of micro-experiments were conducted in a self-made reactor, where hydrates nucleated and grew on the surface of a water droplet immersed in asphaltene-containing oil. Based on the micro-observations, the shape and growth rate of the hydrate shell formed at the oil–water interface were mainly investigated and the effects of asphaltene on hydrate growth were analyzed. According to the experimental results, the shape of the water droplet and the interfacial area changed significantly after the formation of the hydrate shell when the asphaltene concentration was higher than a certain value. A mechanism related to the reduction of the interfacial tension caused by the absorption of asphaltenes on the interface was proposed for illustration. Moreover, the growth rate of the hydrate shell decreased significantly with the increasing asphaltene concentration under experimental conditions. The conclusions of this paper could provide preliminary insight how asphaltene affect hydrate growth at the oil–water interface.

The evolution of the hydrate particle structure during growth and agglomeration under flowing condition affects the particle as well as flow characteristic, which plays an important role in the flow assurance as well as heat transfer in refrigeration systems. Therefore, this article conducts experiments to study and observe the growth and agglomeration process in the main forming stage of hydrate. It was found that the growth of tetrahydrofuran hydrate was anisotropic and in a layered growth pattern. Single crystals generally transformed from octahedral structure to octahedral skeleton structure with growth, however some single crystals also deformed into plate type particles. The thickness of the plate type particles increased gradually during growth, and the edge part increased earlier than the middle part. During agglomeration, the hydrate particles contacted and sintered together. Sand as the impurity didn’t serve as the nucleation center but affected the agglomeration of hydrate particles by collisions. In addition, the effect increased as the sand size decreased. Finally, a microstructure model for hydrate growth and agglomeration was proposed, which showed the hydrate structure evolution in these processes and could lay a foundation for studying the flow assurance of hydrate slurry.

Quantifying the amount of gas hydrate in a reservoir provides valuable insight on gas hydrates’ potential as a resource and their contribution to the global carbon cycle. We develop a new method to estimate hydrate saturation from density-sensitive X-ray computed tomography (XCT) scans of pressure cores from northern Gulf of Mexico (Green Canyon Block 955). While several studies have used XCT to quantify gas hydrate in the fractures of fine-grained sediments, our study is the one of the few to use XCT for coarse-grained (sand and silt) reservoirs. We calibrate our new method with grain density and quantitative degassing measurements from the same intervals. This paper uses the density difference between gas hydrate (0.924 g/cm3) and porewater brine (1.035 g/cm3) and assume these changes linearly affect the XCT measurements allowing for estimates of hydrate saturation. Overall, the XCT calculations agree with the hydrate saturation from quantitative degassing. For example, in core H005-3FB-3, quantitative degassing indicated a hydrate saturation of 88 ±33.5%, while the XCT calculations yielded a 90 ±4 4.8% saturation. These results are encouraging as they suggest that XCT analysis has the potential to nondestructively estimate hydrate saturation.

Massive volumes of gas are sequestered within gas hydrate in subsurface marine sediments in the Gulf of Mexico. Methane associated with gas hydrate is a potentially important economic resource and a significant reservoir of carbon within the global carbon cycle. Nevertheless, uncertainties remain about the genetic source (e.g., microbial, thermogenic) and possible migration history of natural gas incorporated into hydrate. Previous studies have primarily used the hydrocarbon molecular (CH4/C2H6+) and isotopic (δ13C-CH4, δ2H-CH4) compositions of natural gas to address these uncertainties. However, hydrocarbon tracers are altered by mixing, oxidation, secondary methanogenesis, or fluid migration, which presents challenges when deciphering the mechanisms responsible for methane formation and accumulation. To evaluate the genetic source of natural gases from Green Canyon Block 955 (GC 955), east of the Sigsbee escarpment, we collected and analyzed samples from the first pressurized hydrate-bearing sediment cores collected from a coarse-grained hydrate reservoir in the Gulf of Mexico. Gas samples were analyzed for hydrocarbon (C1- C5), major gas (e.g., N2, CO2), and noble gas (He-Xe) abundance and isotopic (e.g., δ13C-CH4, δ2H-CH4, δ13C-CO2, δ15N-N2, 3He/4He, 4He/20Ne) compositions. We determined that natural gas in hydrates from this location are predominantly of primary microbial origin (conservatively at least 76%) and are formed by the hydrogenotrophic (CO2 reduction) methanogenesis pathway. We also note increased thermogenic proportions (~6%) in a hydrate-bearing layer below the main hydrate-bearing interval (separated by a 5 m water-bearing layer). Our results suggest that microbial methane may be abundant below the base of gas hydrate stability at GC 955.

Copper nanowires were synthesized by the wet chemical reduction method using copper sulfate as the copper precursor, aliphatic amines (methylamine, ethanediamine, 1,2-propanediamine) as the inducing reagents, and hydrazine hydrate as the reductant through the aging and reduction processes. The high-resolution transmission electron microscopy (HRTEM) images reveal that the copper nanowires were synthesized by coalescing extremely small-sized copper nanoparticles with the particle sizes of 1–6 nm in copper complex micelles. A longer aging time period favored the coalescing of the copper nanoparticles to form thinner copper nanowires in the following reduction process. The coalescing extent of copper nanoparticles in copper nanowires was highly enhanced by ethanediamine and 1,2-propanediamine as compared with that by methylamine. The copper nanowire-filled polyester films had higher electrical conductivity than the copper nanoparticle-filled ones.

The decomposition of natural gas hydrate will reduce the cementation effect of hydrate and produce ultra-static pore pressure, which will change the mechanical characteristics of the reservoir. Eventually, a series of geological disasters could be triggered, of which the submarine landslide is a typical example. In order to analyze the stability of hydrate-bearing submarine slopes and to explore the internal relationship between hydrate decomposition and submarine landslides, a “two-step reduction method” was described in this paper. This method was based on a strength reduction approach, which can be used to assess the effects of the initial geostress balance and hydrate decomposition on substrate strength reduction. This method was used to reveal the essence of hydrate decomposition and then a joint operation mode of multi-well was proposed. The internal relationship between hydrate decomposition and submarine landslides were analyzed in detail. And the development process and mechanism of submarine landslide were deeply discussed. The results showed that hydrate decomposition is a dynamic process of stress release and displacement, where the “stress inhomogeneity” distributed along the slope is transformed into “displacement inhomogeneity”. We concluded that hydrate decomposition could trigger a submarine landslide, especially along a sliding surface. The formation of submarine landslide is a gradual development process, and presents the dual characteristics of time and space.

Aluminum oxynitride (AlON) powders were synthesized by a novel carbothermal reduction and nitridation (CRN) method. Homogenous and fluffy AlOOH/C core-shell nanoparticle precursor was hydrothermally synthesized with aluminum nitrate hydrate, sucrose and urea as starting materials. Then single-phase AlON powders were synthesized by CRN method at 1700 °C for 2 h. The phase transition and growth of Al2O3 particles was effectively retarded by the amorphous carbon nano-layers on the surface of precursor, resulting in significantly lower reaction temperature and further smaller particle size. Based on above fine AlON raw material, transparent AlON ceramic was prepared by pressureless sintering at 1880 ℃ with the in-line transmittance above 80 %.

Methanol has been used to prevent hydrate formation in industrial handling of hydrate forming mixtures containing water for many decades. Ethanol is also used for the same purpose in countries that have easy access to low price ethanol, like for instance Brasil. Common to these small alcohols is that they also have surfactant properties that will promote hydrate formation, but when added to water in sufficient amounts the hydrate prevention characteristics will dominate. These alcohols will primarily prevent heterogeneous hydrate formation on the interface between water and a separate hydrate phase. Alcohol effects on both of these routes to hydrate formation are investigated and compared to experimental data. In particular we also investigate the effects of these small alcohols on Gibbs free energy for the hydrate formed on the new, shifted, stability conditions. Gibbs free energy is generally higher than hydrate formed from pure water. Enthalpies of hydrate formation are also higher for hydrate formed from water containing alcohols. These are negative numbers so in absolute values released formation enthalpy is lower. The presence of these alcohols in water will also prevent homogeneous hydrate formation from dissolved hydrate formers in water. Glycols have more important roles in other routes to hydrate nucleation. Heterogeneous hydrate nucleation towards mineral surfaces is feasible in different ways. Polar hydrate formers like H2S and CO2 can adsorb directly on rust, and as discussed here, is able to form hydrate from adsorbed state on rust surface. Non-polar hydrocarbons like for instance methane might get trapped in structured water and then nucleate to hydrate. Some research on this is published and further research is in progress. Glycols have very strong attraction to rust and corresponding chemical potentials for adsorbed glycols on rust are favourable enough to facilitate phase transition from glycols dissolved in water over to adsorption. Injection of glycol in gas processing plants have been used by industry for many years and in many cases it might even be economically and technically feasible compared to expensive drying units. Exceptions are situations that will lead to water/glycol freezing. But even in multiphase transport of hydrocarbons with various water cuts mixtures of alcohols might be a technically efficient solution in which the small alcohols may be very efficient ass discussed above and glycols may go through adsorption phase transition from water solution over to glycol film on rust and as such prevent hydrate nucleation towards rust surface. This possible strategy requires more theoretical work as well as experimental investigation. On the basis of thermodynamic analysis and calculations of hydrate formation from different routes it is argues that real natural and industrial systems are unable to reach thermodynamic equilibrium. It is therefore a need for a consistent thermodynamic platform with a uniforms reference system for all phases. We propose, and demonstrate, a residual thermodynamic model system for all phases.

Background This report represents the second part (Part 2) of a two-part report on investigating a novel hepatoprotective substance in ume extract. The heated juice concentrate of Japanese apricot (Ume, Prunus mume Sieb. et Zucc.), popularly called ume extract, is known for its health benefits. In Part 1 of this study (presented in this issue together), we reported the identification of the active substance underlying the hepatoprotective potential of ume extract for the first time. The substance, tentatively referred to unknown 1 (UK1), was shown to have the molecular formula C10H11NO9 with a molecular weight of 289. Here (in Part 2), we aimed to decipher the structure of UK1. Moreover, we show that UK1 is formed by heating the components of ume juice. Methods The purified UK1 (≥93.88% purity, containing 6.11% hydrate water) was subjected to nuclear magnetic resonance (NMR) spectroscopic analysis. The structure of UK1 was elucidated by one-dimension (1D)-NMR (1H, 13C, and DEPT135) and 2D-NMR (COSY, HSQC, and HMBC) experiments. Further, the artificial synthesis of UK1 was attempted by heating aqueous solutions containing citric acid and L-asparagine (L-Asn) or L-aspartic acid (L-Asp). The synthetic experiments were performed using a series of solutions of varying concentrations (1-fold, 5-fold, 10-fold, and 15-fold) of citric acid and L-Asn (molar ratio 5: 1). The molar ratio of citric acid and L-Asn (5: 1) was specified to mimic that in ume juice. Results The chemical structure of UK1 was determined as 2-[3-(carboxymethyl)-3-hydroxy-2,5-dioxopyrrolidin-1-yl]butanedioic acid. More simply, UK1 was identified as an imide in which citric acid was bound to Asp. UK1 could be synthesized by heating (110 °C for 4 h) a solution containing citric acid and L-Asn, or citric acid and L-Asp. The yield of UK1 was dependent on the concentrations of citric acid and L-Asn. Conclusions The findings of this study further validate the conclusions made in Part 1 that UK1 is a novel hepatoprotective substance in ume extract. Based on the structure, UK1 is referred to as “ASP citrimide.” This study demonstrates that ASP citrimide is formed by the association of citric acid and L-Asn (or L-Asp) during the heat concentration of ume juice.

The development of environmental friendly low dose hydrate inhibitors like kinetic hydrate inhibitors (KHIs) is of great significance for the flow assurance in oil & gas production and transportation. In this work, a combined molecular dynamic simulation and experimental verification approach was adopted to increase the efficiency of KHIs development. The inhibition effect of a series of copolymers (N-vinylpyrrolidone and N-acrylate) on hydrate growth was studied by using both molecular dynamics simulation and experimental approaches. The simulation results demonstrate that introduction of hydrophobic ester and butyl group in PVP is beneficial for the inhibition. The length of the alkyl chain of ester group plays an important role in improving inhibition performance. PVP-A, the one being introduced butyl ester group into PVP gets the best inhibition effect. In addition, inhibitors can restrict methane bubbles to re-dissolve into the liquid phase, thereby inhibiting the growth of methane hydrate. Increasing the interaction between KHIs and methane can also improve the inhibitory effect of KHIs. The experimental results confirm the reliability of the molecular dynamics simulation.

We explore the use of deep artificial neural networks (DNNs) to impute data to the experimental data reported by the methane hydrate crystal growth at a bubble surface reported in the literature (Ma, et al., 2002; Sun et al., 2007). We use a genetic programming symbolic regressor to propose a novel empirical rate equation as a function of the temperature and the pressure from the new data set.

Nanoparticles are potential candidates for numerous biological as well as chemical applications due to their exotic properties 1 - 3. Low lattice energy ions are found in deep eutectic solvents (DES). A quaternary ammonium salt is frequently complexed with a metal salt or hydrogen bond donor to produce these compounds (HBD) 4 - 6. The green synthesis of nanoparticles using DESs is always eco-friendly and attractive. The current study focuses on the synthesis of mercuric sulphide, Zirconium oxide, Manganese oxide and Copper oxide nanoparticles using the Choline Chloride - Ethylene Glycol DES as the solvent in presence of a reducing agent, hydrazine hydrate. The UV-Visible, FTIR spectra, XRD, SEM and EDAX analysis were carried out on these metal nanoparticles. The average sizes of these metal nanoparticles were found to be 50 to 150 nm. Hence the green synthesis of metal nanoparticles using Ch. Cl – EG can be considered as an alternative route in chemical synthesis of metal nanoparticles.

Co-pyrolyzing gallium nitrate hydrate and melamine, melem, or g-C3N4 generates gallium nitride (GaN) for the conversion of methane to acetonitrile (AcCN). The solid-state-pyrolysis-made GaN catalysts exhibited better activity than commercial GaN. Among the as-prepared catalysts, GaN made using g-C3N4 as the nitrogen precursor with a N/Ga ratio of 2 (i.e., GaN-(C3N4)-(2)) was the most attractive: a high initial methane conversion (12.5%), a high initial AcCN productivity (26 μmol/gcat/min), and an accumulated AcCN yield (3309 μmol/gcat) in a 6-h reaction time were obtained. GaN-(C3N4)-(2) had isolated GaN phases and enriched amorphous C and N species (e.g., sp2 N and C≡N groups). A six-fold cavity of g-C3N4 as the docking port of Ga3+ to elevate the GaN dispersion in solid-state pyrolysis was proposed. The analysis of the structure-activity correlation revealed that the accumulated AcCN yield had an inverse trend with respect to the crystallite size of GaN and the sp3/sp2 ratio of the N environment.

A series of quinoxaline 1,4-di-N-oxide derivatives, which have been proven to be active cytotoxic agents under hypoxic conditionswere synthesized. Ethyl-3-hydroxyquinoxaline-2-carboxylate (1) on reaction with hydrazine hydrate in ethanol yielded 3-hydroxyquinoxaline-2-carbohydrazide(2). This product on condensation with different aromatic aldehydes yielded N-4-bromobenzylidine)-3-hydroxyquinoxaline-2-carbohydrazide(3) which upon reaction with mCPBA in THF resulted in the abovementionedproducts. These derivatives were evaluated for theiranti-bacterial activity using four different strains. A few compounds among them were also evaluated for their anti-tumour activity towards breast cancer (MCF7) and cervical cancer (HeLa) cell lines. Compound 4a showed moderate activity towards breast cancer cell lines (MCF7) and 4b towards cervical cancer cell lines (HeLa). All the compounds were characterized by IR, 1H NMR and Mass spectroscopy.

Compound dimethyl pyridine-2,6-dicarboxylate (1) was synthesized via the reaction of pyridine-2,6-dicarboxylic acid with methanol. Pyridine-2,6-dicarbohydrazide (2) was synthesized via the reaction of compound (1) with hydrazine hydrate compounds of N,N-bis-(sub. benzylidine) pyridine-2,6-dicarbohydrazide (3–8) were synthesized Via the reaction of compound (2) with aromatic aldehyde compounds of N,N-bis(3-chloro(sub,phenyl)-4-oxoazetine-1-yl-pyridine)-2,6-dicarboxamide (9–14) were synthesized via the reaction of compounds (3–8) with chloro acetyl chloride the biological activity for some compounds were tested the synthesized compounds were identified by I.R, C13.N.M.R, H1.N.M.R and melting point.

During open-pit mining operations of phosphates, huge volume of rocks by products are accumulated and deposited in the mine site. The aim of this paper is to investigate the use of marls as an only aluminosilicate precursor to produce alkali-activated geopolymers. Marls from Moroccan phosphate basins are composed of carbonates, quartz and clays. Raw marl was dried, grinded and calcined at 750 °C. After the heat treatment, the calcined powder was activated using a strong alkali solution, which is a mixture of sodium hydroxide and sodium silicate with a ratio of 0.5. The physical and chemical properties of raw and calcined marls were analyzed using TGA, BET, Pycnometer, particle size analyzer, XRF, XRD, FTIR and SEM. Furthermore, elaborated geopolymers were characterized after 7 and 120 days of curing at ambient temperature using XRD, XRF, TGA, SEM and the mechanical behavior was tested by measuring the compressive strength. The results showed the formation of both; C-A-S-H (Calcium aluminum silicate hydrate) and N-A-S-H (Calcium aluminum silicate hydrate) gels with a compressive strength of 38 MPa confirming that marls from phosphate extraction by-products could be used as a source for the elaboration of geopolymers.

Identifying the characteristic properties of gas hydrates – including thermo-physical properties – is essential for determining their formation condition and in turn, controlling their yield/growth-rate for/in various applications/environments. Gathering these properties, during in-situ crystallization of gas hydrates, is rather challenging due to the harsh conditions they form and limited by the lack of co-existence of multiple characterization techniques. Owing to these limitations, crystallization process of some sII type gas hydrates and their characteristic properties are ill-defined. Therefore to unveil the complete picture of crystallization process of sII type gas hydrates, in this study, in-situ formation of a model system “cyclopentane hydrate” was monitored using a customized DSC sample holder with a transparent window on top. To this end, in-situ crystallization of cyclopentane hydrate was simultaneously followed by coupling optical microscopy along with scanning calorimetry. Further, we show that the cyclopentane hydrate formed by consuming a part of fresh water appearing after the fusion of ice instead of at a very low temperature ≤ −20 °C.

Drug-drug cocrystals, which can regulate physicochemical properties of individual drugs and might produce synergistic therapeutic effects, have drawn growing interest in the pharmaceutical industry. In this study, a novel drug-drug (1:1) cocrystal hydrate of slightly water-soluble dihydromyricetin (DMY) and highly water-soluble pentoxifylline (PTX), DMY-PTX•H2O (1), was prepared by a slurry method. The single-crystal X-ray diffraction results reveal that the cocrystal is formed through hydrogen-bonding interactions between hydroxyl groups of DMY and four acceptors of PTX. The dynamic vapour sorption results indicate that the cocrystal displays reduced hydrophilicity compared with DMY. It is found that cocrystal formation narrows the solubility difference between two parent drugs. The equilibrium solubility of PTX decreases greatly, while that of DMY increases slightly. As a result, DMY and PTX are synchronously and sustainedly released from the cocrystal. Further, a synergistic anti-cancer effect of the cocrystal DMY-PTX•H2O (1) on HepG2 cells in vitro at a drug concentration of 100 μM was discovered. This study brings evidence of cocrystallization as a successful approach for synchronous sustained-release of two drugs with substantially different aqueous solubility.

Earth-abundant transition metal-based bifunctional electrocatalysts are promising alternatives to noble metals for overall water electrolysis, but restricted by low activity and durability. Herein, a three-dimensional phosphorus-doped nickel molybdate/nickel molybdate hydrate @phosphates core–shell nanorod clusters on nickel foam self-supported electrode was fabricated by a combined hydrothermal and phosphating process. The phosphorus doping and phosphate coating induced by phosphating process bring in a synergistic effect to improve the electrical conductivity, provide abundant active surface sites and accelerate the surface reaction for nickel molybdate/nickel molybdate hydrate (NiMoO4/NiMoO4·nH2O) heterostructures. These advantages enable the self-supported electrode to exhibit high hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity in 1.0 M KOH with low overpotentials of 148 and 260 mV at 10 mA cm−2, respectively. When it was employed both as anode and cathode, a cell voltage of 1.62 V is only required to reach the current density of 10 mA cm−2 in alkaline solution. Especially, the self-supported electrode reveals outstanding durability, which could maintain over 25 h at 10 mA cm−2 for HER, OER or overall water splitting. This work provides a novel avenue to enhance the electrocatalytic performance of the catalysts by synergistically modulating the intrinsic electrical conductivity, active surface sites and surface reaction.

A new liquid chromatography system in which tetrabutylammonium bromide semiclathrate hydrate (TBAB-SCH) was used as the column-packing material is proposed to evaluate the adsorption mechanisms of polar small molecules on a TBAB-SCH surface. It has been revealed that the more hydrophilic molecules tend to be more strongly retained on the TBAB-SCH/hexane-diethyl ether interface, and the retentions of aromatics (ARs) and crown ethers (CEs) are differently controlled. CEs are likely retained on the TBAB-SCH interface via hydrogen-bond formation as well on water-ice, whereas the retention mechanism of ARs is unique to TBAB-SCH and has not previously been observed on water-ice. This difference between CEs and ARs may arise from differences in the types of polar groups or molecular size. This chromatographic approach will provide useful information for evaluating the adsorption mechanisms of inhibitors for clathrate hydrate agglomeration, which is a common agglomeration problem experienced by industries.

Natural gas hydrates are mostly formed in low-permeability and fractured muddy sedimentary formations. Adding suitable nanoparticles to the drilling fluid system can improve its filtrate resistance and fracture plugging, and effectively weaken the invasion of drilling fluid into the reservoir. However, it is likely that nanoparticles promote hydrate formation and accumulation in wellbores and will induce accidents. Therefore, this study investigated the effect of hydrophilic silica nanoparticles with particle sizes of 30 nm, 60 nm, and 80 nm and concentrations of 0.5–4.0 wt.% on hydrate formation during upward migration of methane gas using a dynamic simulation system for hydrate formation in a wellbore. The experimental results show that under the condition of methane gas migration, hydrophilic silica nanoparticles inhibit hydrate formation. The inhibition effect increased with an increase in the particle size under a constant concentration, whereas it first increased and then decreased with increasing nanoparticle concentration under a constant particle size. The strongest inhibition effect was observed at a hydrophilic silica nanoparticle concentration of 2.0 wt.%. The influence of hydrophilic silica nanoparticles on hydrate formation may be mainly determined by their hydrophilic properties, heat and mass transfer, and gas migration in the wellbore. Our research indicates that hydrophilic silica nanoparticles can be added to hydrate drilling fluid systems if their concentration can be properly controlled.

Drilling in a natural gas hydrate formation is challenging due to the poor consolidation of the formation and the potential evaporation of the hydrate. The unreasonable down-hole pressure of the drilling fluid can not only lead to the wellbore instability, but also change the predrilling condition of the natural gas hydrate formation, thus leading to an instable wellbore. In this paper, the integrated discrete element method (DEM)-computational fluid dynamics (CFD) work flow is developed to study the wellbore instability due to the penetration of the drilling fluid into the hydrate formation during crack propagations. The results show that the difference between in-situ stresses and overpressure directly affect the drilling fluid invasion behavior. The lower hydrate saturation leads to an easier generation of drilling fluid flow channels and the lower formation breakdown pressure. The breakdown pressure increases with the increase of hydrate saturation, this also indicates that hydrates can enhance the mechanical properties of the formation. The induced cracks are initially accompanied with higher pressure of the drilling fluid. According to the rose diagram of the fracture orientation, a wider orientation of the fracture distribution is observed at higher pressure of the invasion fluid.

In order to improve the utilisation rate of the cores of natural gas hydrate samples from the seafloor and broaden the means of the analysis of pressured cores, long-columnar cores obtained by the gravity-piston pressure corer are usually cut into smaller segments, which are then transferred to pressure chambers before they are sent to the laboratory for further analysis. The transfer system for the core of the natural gas hydrate sample in this paper is able to keep the in situ pressure during the transfer process, which can prevent the changing of physicochemical properties of the cores. In addition, the system can also realise the actions of core pushing, cutting and subsampling. The pressure-retaining feature of the transfer system is discussed in this paper, and an experiment was carried out to test the reliability of the pressure retaining of the system. Moreover, the transfer system was tested in the South China Sea twice and showed an excellent performance of pressure maintenance.

Natural gas hydrate is a kind of clean energy with huge reserves, and the saturation (volume percentage of hydrate in pore space of sediments) is the key parameter for determining whether the reservoir is worthy of exploitation. In this work, rapid hydrate dissociation by the combination of heat injection and NaCl inhibitor addition was studied, and an on-site evaluation method for hydrate saturation in sediment samples was proposed by using a core sampler to transfer hydrate samples under pressure. The results showed that the average gas production rate per unit volume was increased significantly to reach 7.22 L/Lr·min-1 by the injection of NaCl aqueous solution with 50.9 °C, which was attributed to the increase of the chemical potential to further accelerate the rate of hydrate dissociation in the presence of NaCl. Furthermore, for the measurement of methane hydrate samples saturation with a volume of 673 cm3 (which contained 1.4 mol hydrates with the saturation of 58%), hydrate saturation could be accurately achieved within 30 min with a relative error lower than 11.7% This work may provide new thoughts for on-site saturation evaluation and rapid dissociation of hydrate samples during natural gas hydrate exploitation.

Recently developed methane clumped isotope techniques provides fresh and novel insights into methane biogeochemistry, which have been unobtainable through other techniques such as conventional stable isotope determinations and molecular composition measurements of hydrocarbons. Nonetheless, the governing processes and mechanisms which control the clumped isotope signatures (Δ13CH3D and Δ12CH2D2) of natural methane samples remain an active area of investigation. Here, we present paired clumped isotope measurements in methane hydrate, which is a major methane reservoir widely distributed along the continental margins and which plays an important role in the global carbon cycle and climate system. Our study aims to shed new light into the fundamental processes of methane clumped isotope effects and their potential to answer fundamental questions regarding the source and migration of methane found in naturally occurring gas hydrate accumulations. Gas hydrate samples were recovered from five shallow marine sediment sites on the eastern margin of the Japan Sea and most of them present Δ13CH3D and Δ12CH2D2 temperatures ranging from ∼15 to ∼170 °C that apparently match expected methane formation temperatures. The distribution of these clumped isotope signatures along the equilibrium line is best explained by the mixing effect of equilibrated thermogenic methane formed at temperatures of 165 ± 15 °C and biogenic methane equilibrated at 1–2 °C, which may result from slow methanogenesis, anaerobic oxidation of methane (AOM), or their combination. The influences of gas migration/diffusion, hydrate formation and dissociation on Δ13CH3D and Δ12CH2D2 values are insignificant. By combining clumped isotope results with other traditional approaches, a thermogenic and two microbial end-members as well as their isotopic compositions were identified and the relative contribution of each end-member was also quantified. The results not only demonstrate the applicability of methane clumped isotope data to identify potential end-members in natural methane samples, but also reveal that more conventional carbon isotope approaches may significantly underestimate the fraction of thermogenic methane present in global gas hydrate reservoirs. Improvements in the accuracy of source apportionment enable us to better understand the formation history and mechanisms of gas hydrate accumulation, as well as the role played by gas hydrate dissociation in past geological events. The estimated formation temperatures of thermogenic end-member can be further applied in reconstruction of the paleo geothermal gradient at the time when the thermogenic methane was formed at marine sedimentary environment.

To investigate the morphological evolution of the whole growth and aggregation processes of hydrate crystals near the gas–liquid interface, we used a high-pressure visual reactor with high-speed camera to capture the micromorphology of hydrate particles in a natural gas + pure water system with pressure from 2.6 MPa to 3.6 MPa and sub-cooling from 4.7 to 6.23°C. The results showed that under low sub-cooling conditions, the amount and size of particles increased first and then decreased in the range of 0–330 μm, and the small particles always dominated. These particles can be roughly classified into two categories: planar flake particles and polyhedral solid particles. Then, the concept of maximum growth dominant particle size was proposed to distinguish the morphological boundary of growth and aggregation. In addition, the micro model was established to better reflect the effects of particle formation process and evolution mechanism near the gas–liquid interface under stirring condition. The results of this study can provide a guidance for flow assurance in multiphase pipeline.

In this study, the Discrete Element Method (DEM) was employed to investigate numerically the effects of hydrate cementation and intermediate principal stress on the stress-dilatancy relation of grain-cementing type methane hydrate-bearing sediment (MHBS) by conducting a series of conventional and true triaxial tests. A novel 3D thermo-hydro-mechanical-chemical (THMC) contact model for MHBS was employed. The numerical results show that with increasing hydrate saturation and back pressure, or decreasing confining pressure, temperature and salinity, the stress-dilation relation of grain-cementing type MHBS evolves from dilation-dominant to bond-dominant. For the clean sand samples, the relationship between the normalized stress ratio η/Mcr and the dilatancy rate d is close under different intermediate principal stress coefficients. However, for the MHBS samples, this relationship is still affected by the intermediate principal stress coefficient b, due to the effect of hydrate cementation.

The natural gas hydrate resources in the South China Sea alone are about 85 trillion cubic meters. In the drilling process of marine gas hydrate, the natural gas hydrate will decompose and produce gas, as the rising of temperature and dropping of the pressure in the annulus. This process will have a significant impact on drilling safety. Therefore, it is necessary to study the wellbore temperature distribution during the drilling of marine hydrate layer. In this paper, the wellbore temperature distribution of safe drilling in hydrated formation is taken as the research goal, and the research status of relevant domestic and international wellbore temperatures was investigated. According to the characteristics of the marine environment and reservoir-forming characteristics of hydrate reservoirs in the South China Sea, the wellbore temperature distribution model of offshore drilling wellbore under the condition of hydrate decomposition was established. The temperature distribution curve of drilling straight wellbore in hydrate layer of South China Sea was obtained. When drilling the hydrate reservoir, the distribution regularity of the wellbore temperature is similar to that of the conventional offshore drilling wellbore. However, the temperature of the wellbore annulus near the hydrate decomposition site is lower than the ambient temperature, mainly due to the hydrate decomposition endothermic. In this paper, the sensitivity analysis of several main parameters of the wellbore temperature distribution of drilling straight wellbore in hydrate layer of South China Sea was carried out. Through the conduction of experiment and numerical simulation, we have get some new findings: (1) The hydrate saturation has little effect on the wellbore temperature; (2) As the drilling fluid displacement increases, the annulus temperature of the wellbore above the mudline increases, and the temperature of the wellbore below the mudline decreases continuously; (3) As the density of the drilling fluid increases, the temperature at the wellhead decreases, and the temperature at the bottom of the well increases slightly; (4) The greater the rate of penetration of the well, the temperature at the upper part of the wellbore decreases, and the temperature at the bottom of the wellbore increases; Among them, the penetration rate has the most obvious effect on the annular temperature. The results are expected to be helpful to guide the drilling process of marine gas hydrate and offer some references.

Gas hydrates are large energy resources with estimated global reserves of approximately 500–10 000 Gt of carbon, which can be extracted from underground reservoirs. In addition, such reservoirs can...

The global amount of energy contained in natural gas hydrates is huge, maybe as much as twice all known conventional fossil fuel sources. Unlike the worldwide distribution of conventional fossil fuels, hydrocarbons trapped in water as hydrate is also available in countries with limited conventional hydrocarbon sources. The development towards lower global emissions of greenhouse gases requires new strategies for the use of hydrocarbons, whether they are available as conventional sources, or in the form of natural gas hydrates. In this work we outline some possible strategies of utilizing hydrocarbon energy sources in a clean and environmentally friendly way. The use of carbon dioxide for producing hydrates is not new. Results from several experimental studies are available. In this work we shed more light on thermodynamic limitations and the need for additives in order to make the approach technically efficient. Through thermodynamic analysis we show that up to 20 mol per cent N2 is feasible in a CO2/N2 injection gas based on ability to form a new hydrate with fee pore water and the released enthalpy needed to dissociate in situ CH4 hydrate. Surfactant is also needed in order to keep the injection gas front free of blocking hydrate films. Small alcohols like methanol and ethanol have surfactant properties. It is demonstrated that even 10 wt% ethanol in liquid pore water still makes it feasible to create a new hydrate from injection gas containing 20 mol per cent N2. Consequences of other components than CH4 in the hydrate are also discussed. And in practical cases with a well-defined source of CO2 it is also important to investigate impact of other components like for instance H2S on the stability of injection gas hydrate, as well as changes in enthalpy of hydrate formation. Another key element of this work is the conversion of produced hydrocarbons over to hydrogen and carbon dioxide using steam cracking. The technology for this is very old and in daily use.

Poly(N-vinylcaprolactam) (PVCap) and related copolymers have been used as kinetic hydrate inhibitors (KHIs) to combat gas hydrate formation in oil and gas field production flow lines. It is known that the addition of certain solvents to the KHI polymer can enhance its ability to hinder gas hydrate formation. In an earlier study, a wide range of alcohols, glycol ethers, and ketones were investigated as synergetic solvents with PVCap. In that study, an outstanding synergetic effect was achieved by 4-methyl-1-pentanol (iHexOl). This report builds on that study by investigating iHexOl in more detail as well as some newly synthesized solvents predicted by the first study to have good synergism. Both slow constant cooling (SCC) and isothermal KHI experiments were conducted in high-pressure steel rocking cells using a structure II-forming natural gas mixture. The KHI polymer concentration, solvent concentration, and mixed solvent systems were investigated. The solvent synergist water solubility, also in brines, and partitioning to the liquid hydrocarbon phase are shown to be important factors to consider for optimizing KHI performance. Further, it was observed that the optimal molecular weight distribution for the KHI polymer when used with a solvent synergist is not the same as the optimum distribution when using the polymer alone.

Mechanisms of growth and dissociation, growth rates, and morphology of gas hydrates of methane, carbon dioxide, and two CH4:CO2 mixtures (80:20 and 30:70 nominal concentration) were studied using using high resolution images and very precise temperature control. Subcooling and a recently proposed mass transfer-based driving force were used to analyze the results. When crystal growth rates did not exceed 0.01 mm/s, all systems showed faceted, euhedral crystal habits at low driving forces. At higher driving forces and growth rates, morphologies were different for all systems. These results solve apparent contradictions in literature about the morphology of hydrates of methane, carbon dioxide, and their mixtures. Differences in the growth mechanism of methane-rich and carbon dioxide-rich hydrates were elucidated. It was also shown that hydrate growth of methane, carbon dioxide, and their mixtures proceed via partial dissociation of the growing crystal. Temperature gradients were used to dissociate hydrates at specific locations, which revealed a most interesting phenomenon: On dissociation, carbon dioxide-rich hydrates propagated onto the bare substrate while drawing water from the opposite side of the sample. Furthermore, it was shown that an abrupt change in morphology common to all systems could be correlated to a change in the slope of growth rate data. This change in morphology was explained by a shift in the crystal growth mechanism.

Diimine (HN═NH) is a strong reducing agent, but the efficiency of diimine oxidized from hydrazine hydrate or its derivatives is still not good enough. Herein, we report an in situ neocuproine-copper complex formation method. The redox potential of this complex enable it can serve as an ideal redox catalyst in the synthesis of diimine by oxidation of hydrazine hydrate, and we successfully applied this technique in the reduction of alkynes. This reduction method displays a broad functional group tolerance and substrate adaptability as well as the advantages of safety and high efficiency. Especially, nitro, benzyl, boc, and sulfur containing alkynes can be reduced to the corresponding alkanes directly, which provides a useful complementary method to traditional catalytic hydrogenation. Besides, we applied this method in the preparation of the Alzheimer's disease drug CT-1812 and studied the mechanism.

A novel, efficient, and atom-economical approach for the construction of quinazolinones from 2-nitrobenzaldehydes has been unveiled via copper-catalyzed nitrile formation, hydrolysis, and reduction in one pot for the first time. In this reaction, urea is used as a source of nitrogen for nitrile formation, hydrazine hydrate is used for both the reduction of the nitro group and the hydrolysis of nitrile, and atmospheric oxygen is used as the sole oxidant. The method portrays a wide substrate scope with good functional group tolerances. Moreover, this method was applied for the synthesis of schizocommunin, tryptanthrin, phaitanthrin-A, phaitanthrin-B, and 8H-quinazolino[4,3-b]quinazolin-8-one.

Dentro da química sustentável, os hidratos de gás estão ganhando destaque devido às suas inovadoras aplicações, em diferentes contextos científicos e industriais. A capacidade de entender e controlar suas propriedades são cruciais para o pleno desenvolvimento de tecnologias baseadas em hidratos. Neste contexto, a partir do modelo matemático publicado por Vlasov para a formação de hidrato de metano, o presente estudo busca o desenvolvimento de um código computacional capaz de simular o grau de formação de diferentes hidratos de gás, em quaisquer condições termodinâmicas, com a vantagem de reduzir a quantidade de experimentos necessários para a avaliação do seu comportamento de formação. Para avaliar a viabilidade na simulação de formação de outras composições de hidratos de gás, o código foi utilizado para simular a formação do hidrato de ciclopentano. O modelo computacional idealizado apresentou sucesso na reprodução numérica das curvas experimentais para o hidrato de metano, apresentando o maior erro de 19,73%. Os resultados apresentados neste trabalho mostram-se coerentes frente à literatura, fornecendo meios de observação da influência das condições experimentais iniciais até a etapa final de formação. Ainda, o código computacional apresenta um caráter global, pois permite simular diferentes composições de hidratos de gás, com promissora aplicação no desenvolvimento de processos baseados na tecnologia de hidratos.

An economic, sustainable, and straightforward environmentally friendly route for synthesis of 3-methyl-4-aryl-1,4-dihydropyrazolo[4ʹ,3ʹ:5,6]pyrano[2,3-d]pyrimidine-5,7(6H,8H)-diones via condensation of ethyl acetoacetate, hydrazine hydrate, barbituric acid, and aromatic aldehydes in the presence of catalytic amount of H3PMo7W5O40·24H2O under solvent-free condition was reported. This environmentally benign protocol offers selective synthesis of pyrazolopyranopyrimidine derivatives without any side product with excellent yield in shorter time.

An efficient SO42−–ZrO2–TiO2 super acid catalyst was fabricated via simple impregnation precipitation strategy and applied in one-step synthesis of adipicdihydrazide (ADH). The purity and yield of ADH reached up to 97.5 and 96.7% respectively without separation treatment. After five recycling of the catalyst, the ADH yield still remained 82%, revealing the excellent stability performance of SO42−–ZrO2–TiO2 catalyst. Further, the excellent catalytic performance could be attributed to (1) solid super acid existed in SO42−–ZrO2–TiO2; (2) robust SO42− maintained in ZrO2–TiO2; (3) the accelerated cleavage of C =O and improved nucleophilic attack reaction rate of hydrazine hydrate by vast proton produced. DFT calculation was employed to further analyze the electron cloud change of ZrO2–TiO2 with the SO42− introduction and calculate the adsorption energy barrier of SO42−–ZrO2–TiO2 for AA (− 2.08 eV). An efficient SO42−-ZrO2-TiO2 super acid catalyst was fabricated via simple impregnation precipitation strategy and applied in one-step synthesie of adipic dihydrazide. The resulting acidic centers of SO42−-ZrO2-TiO2 attracted electrons from surrounding water molecules to restore neutrality. Meanwhile, a large amount of H+ floated around in the reaction system, which could break the C=O double bond and improve the adipic acid conversion rate. The extreme catalytic activity was based on the fact that the electronic effects of SO42− and ZrO2-TiO2 facilitated the interaction with H+ in adipic acid and reduced hydrazine hydrate nucleophilic attack difficulty.