Clathrate Formation Research Articles

Tuneable mesoporous silica material for hydrogen storage application via nano-confined clathrate hydrate construction

Safe storage and utilisation of hydrogen is an ongoing area of research, showing potential to enable hydrogen becoming an effective fuel, substituting current carbon-based sources. Hydrogen storage is associated with a high energy cost due to its low density and boiling point, which drives a high price. Clathrates (gas hydrates) are water-based (ice-like) structures incorporating small non-polar compounds such as H2 in cages formed by hydrogen bonded water molecules. Since only water is required to construct the cages, clathrates have been identified as a potential solution for safe storage of hydrogen. In bulk, pure hydrogen clathrate (H2O-H2) only forms in harsh conditions, but confined in nanospaces the properties of water are altered and hydrogen storage at mild pressure and temperature could become possible. Here, specifically a hydrophobic mesoporous silica is proposed as a host material, providing a suitable nano-confinement for ice-like clathrate hydrate. The hybrid silica material shows an important decrease of the pressure required for clathrate formation (approx. 20%) compared to the pure H2O-H2 system. In-situ inelastic neutron scattering (INS) and neutron diffraction (ND) provided unique insights into the interaction of hydrogen with the complex surface of the hybrid material and demonstrated the stability of nano-confined hydrogen clathrate hydrate.

Interplay between the Formation of Colloidal Clathrate and Cubic Diamond Crystals.

Controlling the valency of directional interactions of patchy particles is insufficient for the selective formation of target crystalline structures due to the competition between phases of similar free energy. Examples of such are stacking hybrids of interwoven hexagonal and cubic diamonds with (i) its liquid phase, (ii) arrested glasses, or (iii) clathrates, all depending on the relative patch size, despite being within the one-bond-per-patch regime. Herein, using molecular dynamics simulations, we demonstrate that although tetrahedral patchy particles with narrow patches can assemble into clathrates or stacking hybrids in the bulk, this behavior can be suppressed by the application of external surface potential. Depending on its strength, the selective growth of either cubic diamond crystals or empty sII clathrate cages can be achieved. The formation of a given ordered network depends on the structure of the first adlayer, which is commensurate with the emerging network.

Mesomorphology of clathrate hydrates from molecular ordering.

Clathrate hydrates are crystals formed by guest molecules that stabilize cages of hydrogen-bonded water molecules. Whereas thermodynamic equilibrium is well described via the van der Waals and Platteeuw approach, the increasing concerns with global warming and energy transition require extending the knowledge to non-equilibrium conditions in multiphase, sheared systems, in a multiscale framework. Potential macro-applications concern the storage of carbon dioxide in the form of clathrates, and the reduction of hydrate inhibition additives currently required in hydrocarbon production. We evidence porous mesomorphologies as key to bridging the molecular scales to macro-applications of low solubility guests. We discuss the coupling of molecular ordering with the mesoscales, including (i) the emergence of porous patterns as a combined factor from the walk over the free energy landscape and 3D competitive nucleation and growth and (ii) the role of molecular attachment rates in crystallization-diffusion models that allow predicting the timescale of pore sealing. This is a perspective study that discusses the use of discrete models (molecular dynamics) to build continuum models (phase field models, crystallization laws, and transport phenomena) to predict multiscale manifestations at a feasible computational cost. Several advances in correlated fields (ice, polymers, alloys, and nanoparticles) are discussed in the scenario of clathrate hydrates, as well as the challenges and necessary developments to push the field forward.

ASPHALT- RESIN- PARAFFIN ASSOCIATION CRUSHING IN THE VOLUME OF OIL AND OIL EMULSION WITH NEW NANOSTRUCTURE COORDINATION POLYMERS

A short list of existing methods for the prevention and removal of asphalt-resin-paraffin deposits from oilfield equipment is given. Chemical methods related to the use of various additives, reagents, and remover agents are discussed in more detail. A brief description of the main classes of chemicals used in solving the problem of preventing and removing asphalt-resin-paraffin deposits is given. It has been shown that in order to select the most chemically effective ways to prevent and remove organic deposits, it is necessary to obtain an adequate understanding of the composition, properties, and structure of the source oil and the formed deposits. The mechanism of action of the reagents on asphalt-resin-paraffin deposits was clarified, and it was established that the reagents BAF-1 and BAF-2 (technical conditional name of composites) when interacting with the deposits, grind the associates and ensure their uniform distribution in the oil, which improves the rheological properties of the oil. It is indicated that the technology being put forward is based on the clathrate formation, i.e. Lewis's theory of "host-guest". Keywords: asphalt-resin-paraffin deposits, crushing, factors affecting the formation of ARPD, coagulation, the chemical composition of oil, mechanism of ARPD formation, methods of ARPD control.

Evidence of Spontaneous Formation of Two-Dimensional Amorphous Clathrates on Superhydrophilic Surfaces.

Clathrate hydrates reserved in the seabed are often dispersed in the pores of coarse-grained sediments; hence, their formation typically occurs under nanoconfinement. Herein, we show the first molecular dynamics (MD) simulation evidence of the spontaneous formation of two-dimensional (2D) clathrate hydrates on crystal surfaces without conventional nanoconfinement. The kinetic process of 2D clathrate formation is illustrated via simulated single-molecule deposition. 2D amorphous patterns are observed on various superhydrophilic face-centered cubic surfaces. Notably, the formation of 2D amorphous clathrate can occur over a wide range of temperatures, even at room temperature. The strong water-surface interaction, the characteristic properties of guest-gas molecules, and the underlying surface structure dictate the formation of 2D amorphous clathrates. Semiquantitative phase diagrams of 2D clathrates are constructed where representative patterns of 2D clathrates for characteristic gas molecules on prototypical Pd(111) and Pt(111) surfaces are confirmed by independent MD simulations. A tunable pattern of 2D amorphous clathrates is demonstrated by changing the lattice strain of the underlying substrate. Moreover, ab initio MD simulations confirm the stability of 2D amorphous clathrate. The underlining physical mechanism for 2D clathrate formation on superhydrophilic surfaces is elucidated, which offers deeper insight into the crucial role of water-surface interaction.

Zr-Porphyrin Metal-Organic Framework as nanoreactor for boosting the formation of hydrogen clathrates.

We report the first experimental evidence for rapid formation of hydrogen clathrates under mild pressure and temperature conditions within the cavities of a zirconium-metalloporphyrin framework, specifically PCN-222. PCN-222 has been selected for its 1D mesoporous channels, high water-stability, and proper hydrophilic behavior. Firstly, we optimize a microwave (MW)-assisted method for the synthesis of nanosized PCN-222 particles with precise structure control (exceptional homogeneity in morphology and crystalline phase purity), taking advantage of MW in terms of rapid/homogeneous heating, time and energy savings, as well as potential scalability of the synthetic method. Second, we explore the relevance of the large mesoporous 1D open channels within the PCN-222 to promote the nucleation and growth of confined hydrogen clathrates. Experimental results show that PCN-222 drives the nucleation process at a lower pressure than the bulk system (1.35 kbar vs 2 kbar), with fast kinetics (minutes), using pure water, and with a nearly complete water-to-hydrate conversion. Unfortunately, PCN-222 cannot withstand these high pressures, which lead to a significant alteration of the mesoporous structure while the microporous network remains mainly unchanged.

Probing the critical nucleus size in tetrahydrofuran clathrate hydrate formation using surface-anchored nanoparticles

Controlling the formation of clathrate hydrates is crucial for advancing hydrate-based technologies. However, the microscopic mechanism underlying clathrate hydrate formation through nucleation remains poorly elucidated. Specifically, the critical nucleus, theorized as a pivotal step in nucleation, lacks empirical validation. Here, we report uniform nanoparticles, e.g., graphene oxide (GO) nanosheets and gold or silver nanocubes with controlled sizes, as nanoprobes to experimentally measure the size of the critical nucleus of tetrahydrofuran (THF) clathrate hydrate formation. The capability of the nanoparticles in facilitating THF clathrate hydrate nucleation displays generally an abrupt change at a nanoparticle-size-determined specific supercooling. It is revealed that the free-energy barrier shows an abrupt change when the nanoparticles have an approximately the same size as that of the critical nucleus. Thus, it is inferred that THF clathrate hydrate nucleation involves the creation of a critical nucleus with its size being inversely proportional to the supercooling. By proving the existence and determining the supercooling-dependent size of the critical nucleus of the THF clathrate hydrates, this work brings insights in the microscopic pictures of the clathrate hydrate nucleation.

Zr‐Porphyrin Metal–Organic Framework as nanoreactor for boosting the formation of hydrogen clathrates

AbstractWe report the first experimental evidence for rapid formation of hydrogen clathrates under mild pressure and temperature conditions within the cavities of a zirconium‐metalloporphyrin framework, specifically PCN‐222. PCN‐222 has been selected for its 1D mesoporous channels, high water‐stability, and proper hydrophilic behavior. Firstly, we optimize a microwave (MW)‐assisted method for the synthesis of nanosized PCN‐222 particles with precise structure control (exceptional homogeneity in morphology and crystalline phase purity), taking advantage of MW in terms of rapid/homogeneous heating, time and energy savings, as well as potential scalability of the synthetic method. Second, we explore the relevance of the large mesoporous 1D open channels within the PCN‐222 to promote the nucleation and growth of confined hydrogen clathrates. Experimental results show that PCN‐222 drives the nucleation process at a lower pressure than the bulk system (1.35 kbar vs 2 kbar), with fast kinetics (minutes), using pure water, and with a nearly complete water‐to‐hydrate conversion. Unfortunately, PCN‐222 cannot withstand these high pressures, which lead to a significant alteration of the mesoporous structure while the microporous network remains mainly unchanged.

Separation of Propane and Propylene by Urea Clathrate Formation

Separation of Propane and Propylene by Urea Clathrate Formation

Timing and Abundance of Clathrate Formation Control Ocean Evolution in Outer Solar System Bodies: Challenges of Maintaining a Thick Ocean within Pluto

Clathrate hydrates may represent a sizable fraction of material within the icy shells of Kuiper Belt objects and icy moons. They influence the chemical and thermal evolution of subsurface oceans by locking volatiles into the ice shell and by providing more thermal insulation than pure water ice. We model the formation of these crystalline compounds in conditions relevant to outer solar system objects, using Pluto as an example. Although Pluto may have hosted a thick ocean in its early history, Pluto’s overall heat budget is probably insufficient to preserve liquid today if its outer shell is pure water ice. One previously proposed reconciliation is that Pluto’s ocean has a winter jacket: an insulating layer of methane clathrate hydrates. Unfortunately, assessments of the timing, quantity, and type of clathrate hydrates forming within planetary bodies are lacking. Our work quantifies the abundance of clathrate-forming gases present in Pluto’s ocean from accreted ices and volatiles released during thermal metamorphism throughout Pluto’s history. We find that if Pluto formed with the same relative abundances of ices found in comets, then a buoyant layer of mixed methane and carbon dioxide clathrate hydrates may form above Pluto’s ocean, though we find it insufficient to preserve a thick ocean today. In general, our study provides methodology for predicting clathrate formation in ocean worlds, which is necessary to predict the evolution of the ocean’s composition and whether a liquid layer remains at present.

The gelation mechanism of mung bean starch as affected by edible alum

Abstract To understand the gelation mechanism of mung bean starch (MBS) as affected by addition of edible alum, the physicochemical properties of MBS gels and their gelation process under 0–0.25 % of alum addition were studied. The results showed that alum incorporation enhanced the gel texture and starch-water interaction in a concentration-dependent manner. With increasing amount of alum addition, the pH value and ζ-potential of MBS decreased, while the swelling power, pasting viscosity, the leached amylose content, gelation temperature, short-range ordered structure and the crystallinity of MBS gels increased. It is believed that alum addition improved the texture of MBS gels by promoting amylose leaching, starch aggregation and recrystallization. The increase in starch-water interaction might be due to the destruction of MBS structure by polar ions and the formation of clathrates by leached amylose and Al3+ ions.

Accelerated methane storage in clathrate hydrates using mesoporous (Organo-) silica materials

Methane (CH4) clathrate hydrates have gained much attention in the ever-growing search for novel energy storage methods; however, they are currently limited due to their poor water-to-hydrate conversions and slow formation kinetics. To surmount these bottlenecks, significant research has been centered on the design of novel methods (porous media). In this vein, the present work explores two hydrophobic mesoporous solids, an alkyl-grafted mesoporous silica (SBA-15 C8) and a periodic mesoporous organosilica (Ring-PMO), in their ability to promote CH4 clathrates. Both materials have shown to facilitate CH4 clathrate formation at mild operating conditions (6 MPa and 269–276 K). The study revealed that the maximal CH4 storage capacities are strongly linked to the critical/optimal quantity of water in the system which was determined to be at 130% and 200% of the pore volume for SBA-15 C8 and Ring-PMO, respectively. Up to 90% and 95% of the maximum water-to-hydrate conversions were achieved in 90 min at the lowest experimental temperature and critical water content for SBA-15 C8 and Ring-PMO, respectively. At these conditions, SBA-15 C8 and Ring-PMO showed a maximum gas uptake of 98.2 and 101.2 mmol CH4/mol H2O, respectively. Both the materials exhibited no chemical or morphological changes post-clathrate formations (characterized using FT-IR, N2 sorption, XRD, and TEM), inferring their viability as clathrate promoters for multiple cycles. An integrated multistep model was considered adequate for representing the hydrate crystallization kinetics and fits well with the experimental kinetic data with a low average absolute deviation in water-to-hydrate conversions among the three distinct kinetic models analyzed. Overall, the results from this study demonstrate hydrophobic porous materials as effective promoters of CH4 clathrates, which could make clathrate-based CH4 storage and transport technology industrially viable.

Formation and Transformation of Clathrate Hydrates under Interstellar Conditions.

ConspectusContinuing efforts by many research groups have led to the discovery of ∼240 species in the interstellar medium (ISM). Observatory- and laboratory-based astrochemical experiments have led to the discovery of these species, including several complex organic molecules (COMs). Interstellar molecular clouds, consisting of water-rich icy grains, have been recognized as the primordial sources of COMs even at extremely low temperatures (∼10 K). Therefore, it is paramount to understand the chemical processes of this region, which may contribute to the chemical evolution and formation of new planetary systems and the origin of life.This Account discusses our effort to discover clathrate hydrates (CHs) of several molecules and their structural varieties, transformations, and kinetics in a simulated interstellar environment. CHs are nonstochiometric crystalline host-guest complexes in which water molecules form cages of different sizes to entrap guest molecules. CHs are abundant on earth and require moderate temperatures and high pressures for their formation. Our focus has been to form CHs at extremely low pressure and temperature as in the ISM, although their existence under such conditions has been a long-standing question since water and guest molecules (CH4, CO2, CO, etc.) exist in space. In multiple studies conducted at ∼10-10 mbar, we showed that CH4, CO2, and C2H6 hydrates could be formed at 30, 10, and 60 K, respectively. Well-defined IR spectroscopic features supported by quantum chemical simulations and temperature-programmed desorption mass spectrometric analyses confirmed the existence of the 512 (for CH4 and CO2) and 51262 (for C2H6) CH cages. Mild thermal activation for long periods under ultrahigh vacuum (UHV) allowed efficient molecular diffusion, which is crucial for forming CHs. We also explored the formation of THF hydrate (a promoter/stabilizer for binary CHs), and a spontaneous method was found for its formation under UHV. In a subsequent study, we observed a binary THF-CO2 hydrate and its thermal processing at 130 K leading to the transportation of CO2 from the hydrate cages to the matrix of amorphous water. The findings imply that such systems possess a dynamic setting that facilitates the movement of molecules, potentially accounting for the chemical changes observed in the ISM. Furthermore, an intriguing fundamental phenomenon is the consequences of these CHs and their dynamics. We showed that preformed acetone and formaldehyde hydrates dissociate to form cubic (Ic) and hexagonal (Ih) ices at 130-135 K, respectively. These unique processes could be the mechanistic routes for the formation of various ices in astrophysical environments.Other than adding a new entry, namely, CHs, to the list of species found in ISM, its existence opens new directions to astrochemistry, observational astronomy, and astrobiology. Our work provides a molecular-level understanding of the formation pathways of CHs and their transformation to crystalline ices, which sheds light on the chemical evolution of simple molecules to COMs in ISM. Furthermore, CHs can be potential candidates for studies involving radiation, ionization, and electron impact to initiate chemical transformations between the host and guest species and may be critical in understanding the origin of life.

Molecular basis for inhibition of methane clathrate growth by a deep subsurface bacterial protein.

Methane clathrates on continental margins contain the largest stores of hydrocarbons on Earth, yet the role of biomolecules in clathrate formation and stability remains almost completely unknown. Here, we report new methane clathrate-binding proteins (CbpAs) of bacterial origin discovered in metagenomes from gas clathrate-bearing ocean sediments. CbpAs show similar suppression of methane clathrate growth as the commercial gas clathrate inhibitor polyvinylpyrrolidone and inhibit clathrate growth at lower concentrations than antifreeze proteins (AFPs) previously tested. Unlike AFPs, CbpAs are selective for clathrate over ice. CbpA3 adopts a nonglobular, extended structure with an exposed hydrophobic surface, and, unexpectedly, its TxxxAxxxAxx motif common to AFPs is buried and not involved in clathrate binding. Instead, simulations and mutagenesis suggest a bipartite interaction of CbpAs with methane clathrate, with the pyrrolidine ring of a highly conserved proline residue mediating binding by filling empty clathrate cages. The discovery that CbpAs exert such potent control on methane clathrate properties implies that biomolecules from native sediment bacteria may be important for clathrate stability and habitability.

Neon encapsulation by a hydroquinone organic crystalline clathrate under ambient conditions

The recent use of noble gases in laser devices and semiconductor lithography has greatly increased. However, there is no commercial technology for the storage of noble gases in solid materials owing to their chemical inertness and relative lightness. Here we report the simple synthesis and characteristics of a hydroquinone clathrate that stably captures neon at atmospheric pressure and room temperature. The highly flexible structure enables neon encapsulation in the one-dimensional channels of the clathrate framework despite their inter-cage migration through the hexagonal entrance of the cages. The neon uptake of as-synthesized hydroquinone clathrates is 37.3 g L−1 at 1 bar and 298 K. Increasing the temperature accelerates the release of neon from the flexible hydroquinone clathrate hydrogen-bonded organic framework, leading to guest-free clathrate formation at 1 bar and 400 K. This method represents a technological development for better storage and the controlled release of noble gases in solid structured materials.

Colored Wastewater Treatment by Clathrate Hydrate Technique

Numerous recent studies have shown that discharging colored wastewater into the environment causes contamination, which has adverse impact due to textile, dyeing, and food industries. The current study presents experimental research on the clathrate hydrate technique used for producing pure water from of wastewater contaminated by dyes. Under constant starting conditions, the clathrate formation for binary (water + refrigerant gas) and ternary (water + refrigerant gas + promotor) systems were studied. The R134a gas was used along with Cyclohexane (2.5 vol%), Tween 80 (100 ppm), and silica gel powder as promotors (100 ppm). Moreover, povidone-iodine (500, 2500, and 5000 ppm) and potassium permanganate (10, 50, and 100 ppm) were used as colored compounds in order to prepare synthetic wastewater (model wastewater). The production of hydrates, which rapidly captured the refrigerant gas molecules in the solid phase, was primarily responsible for the pressure drop. Both povidone-iodine and potassium permanganate have a negligible impact on the hydrate formation rates. It was found that the concentration of povidone-iodine and potassium permanganate in the produced water was decreased. As far as we know, the method of using clathrate hydrate to remove the dyes in water has never been investigated. The results showed that the povidone-iodine removal efficiency ranged between 86% and 92%, and the potassium permanganate removal efficiency ranged between 90% and 95%. The removal efficiency was improved by adding promotors, which increased the dissolved gas quantity and the amount of water hydrates. The maximum removal efficiency was accomplished using silica gel powder and cyclohexane, which are more significant than in pure water and Tween 80. This study demonstrated the viability of the clathrate hydrate technique as a green technology for the treatment of colored wastewater effluents from different industries.

Crystal Engineering, Electron Conduction, Molecular Recognition and Reactivity by Chalcogen Bonds in Tetracyanoquinodimethanes Fused with [1,2,5]Chalcogenadiazoles

AbstractStudies on a series of tetracyanoquinodimethanes (TCNQs) fused with [1,2,5]chalcogenadiazole rings reveals that chalcogen bonds (ChBs), through E•••N≡C (E = S or Se) contacts, are a decisive factor in determining their crystal structures, with the formation of one- or two-dimensional networks in a lateral direction. For anion-radical salts generated by one-electron reduction, electron conduction occurs in the direction of the network due to intermolecular electronic interactions involving ChBs. Based on the reliable synthon E•••N≡C for crystal engineering, molecular recognition occurs so that solid-state molecular complexes are selectively formed with certain donors, such as xylenes, among their isomers by charge-transfer-type clathrate formation. The inclusion cavity of the clathrate might provide a reaction environment for photoinduced electron transfer in the solid state. The accommodation of multiple conformers of overcrowded ethylene exhibiting thermo/mechanochromism is another example of a novel function that can be realized by ChBs through E•••N≡C contacts. Therefore, these chalcogenadiazolo-TCNQs endowed with the ability to form ChBs are promising materials for the development of novel solid-state functions.1 Introduction2 Bis[1,2,5]thiadiazolo-TCNQ (BTDA)2.1 Chalcogen Bonds in Crystal Structures of BTDA and its Se Analogues2.2 Electronic Effects of Chalcogen Bonds in Organic Conductors Consisting of BTDA2.3 Molecular Recognition by Chalcogen Bonds in Molecular Complexes of BTDA2.4 Single-Crystalline-State Photoreactions of Molecular Complexes of BTDA2.5 Overcrowded Ethylene Composed of a BTDA Substructure3 TCNQ Analogues Fused with a [1,2,5]Chalcogenadiazole3.1 Crystal Structures of Chalcogenadiazolo-TCNQs3.2 Crystal Structures of Chalcogenadiazolo-TCNNQs: An E•••N≡C Chalcogen Bond versus a Weak C–H•••N≡C Hydrogen Bond3.3 Molecular Recognition by Chalcogen Bonds in TCNNQ Derivatives4 Outlook

Geology, geochemistry, fluid inclusion data, stable isotope characteristics, and ore genesis of the Barout Aghaji gold deposit, NW Zanjan, Iran

The Barout Aghaji gold deposit is located ∼90 km northwest of Zanjan, within the Takab-Takht-e-Soleyman subzone of the Sanandaj-Sirjan metamorphosed-deformed zone. Ore-bearing quartz veins are hosted by Neoproterozoic amphibolite and Eocene to Oligocene granitic gneisses. Oligo-Miocene Upper Red Formation unconformably overlies the amphibolite and granitic gneisses. Field observations and petrographic studies show that two deformation stages occurred in this area. The first deformation stage was ductile, producing mylonitic and proto-mylonitic microstructures, but the second one was brittle, represented by sheeted quartz veins and veinlets. In the first stage, barren milky quartz veins occurred containing minor sulfide minerals, but dark to light gray ore-bearing quartz veins and veinlets are formed in the latter stage. The mineralized veins appear as massive microcrystalline quartz cut by sheeted quartz veins with comb, druse, and crustiform textures. The gold-bearing quartz veins contain as much as 3% sulfide minerals. Pyrite is the main sulfide mineral and is associated with minor chalcopyrite. Sulfides are commonly altered to hematite, goethite, and rarely malachite. Hydrothermal alteration around the quartz veins consists of silicification, pyritization, and sericitization. The whole-rock geochemistry of the collected samples from the granitic gneisses and quartz veins shows that Au is enriched in the quartz veins (average of 114 ppb) relative to host rocks (average of 22.5 ppb). Au shows strong positive correlations with As, Ba, Mo, Pb, Sc, Tl, Ag, and negative correlations with Cu, Bi, Se, and Te in the granitic gneisses. It also shows strong positive correlations with S, Hg, Th, Co, Bi, Pb, and Ag and negative correlations with P, V, Te, W, Sc, Zn in quartz veins. Four types of primary fluid inclusions were identified, including type I, two-phase aqueous-rich fluid inclusions (liquid > vapor; LV); type II, two-phase vapor-rich fluid inclusions (gas > liquid; VL); type III, three-phase fluid inclusions containing CO2 with clathrate formation (L1L2V); and type IV three-phase fluid inclusions (aqueous, vapor, and solid; LVS). The homogenization temperatures of fluid inclusions in auriferous quartz veins range from 199 −446 with a mode of 270–300 °C. Salinities range from 0.8 to 49.02 wt% NaCl Equiv. with two distinct populations at 0.8–8.5 and 31.1–49.02 wt% NaCl Equiv. The large variations in the homogenization temperatures and salinities can be attributed to the cooling and isothermal mixing of fluids. The δ34S values for four pyrites separated from auriferous quartz veins range from +2.9 to +7.1‰, with an average of 4.5‰. δ34S values of fluids in equilibrium with pyrite were calculated from +3.5 to +7.3‰, with an average of 5.4‰, indicating a metamorphic source for the sulfur using temperatures estimated from the fluid inclusion study. The Field observations, vein textures, mineralogy, ore geochemistry, fluid inclusion studies, and sulfur isotope data indicate that gold mineralization in the Barout Aghaji area has many similarities to orogenic and intrusion-related gold deposits, such that low salinity fluids derived from metamorphic rocks are mixed with high salinity fluid inclusions possibly derived from granitic gneisses during syn to post tectonic magmatism.

Microscopic Insights into the Effects of Anti-Agglomerant Surfactants on Surface Characteristics of Tetrahydrofuran Hydrate

The formation of clathrate hydrates in pipelines is potentially threatening to exploration and gas transportation in the petroleum industry. To reduce such risks, various surfactants have been explored as anti-agglomerants to prevent the aggregation of hydrate particles. However, the anti-agglomeration mechanisms are not yet fully understood. In this study, modified atomic force microscopy is first developed to investigate the effects of two surfactants, namely, 1-naphthaleneacetic acid and dodecylbenzenesulfonic acid, on the surface of a tetrahydrofuran (THF) hydrate. The surfactants have remarkable effects in terms of changing the grain size and decreasing the grain boundary depth and surface roughness of the THF hydrate. In addition, the surfactants reduce the quasi-liquid layer (QLL) thickness of the THF hydrate and the adhesion forces between the hydrate and the microsphere probe. This phenomenon may be caused by the changes induced by surfactant molecules on the water–guest molecule structure near the gas/water interface. Thus, hydrate growth is enhanced in the QLL. The adhesion forces decrease linearly with QLL thickness after adding the surfactants. These findings indicate that surfactants reduce the adhesion forces by reducing the QLL thickness at higher temperatures. The effects of surfactants on the QLL thickness and surface morphology of the hydrate are investigated, providing critical information on the cohesive behaviors among hydrate particles or between hydrate particles with other materials. Our work provides new insights into the underlying mechanism of how surfactants prevent hydrate aggregation, which is crucial in hydrate-related safety management.

Engineering of hollow periodic mesoporous organosilica nanorods for augmented hydrogen clathrate formation

Careful engineering of the surface chemistries of porous additives for H2 clathrate formation could enhance the H2 storage capacities, a vital requirement for their use as alternative H2 storage medium.