Trace Amounts Of Water Research Articles

Carbon dots for efficient detection of water content in organic solvents

The trace amount of water in organic solvents can affect the progress of chemical reactions, which will adversely affect chemical production in many industries, resulting in a doubling of costs. In this work, carbon dots (CDs) with abundant polar groups were synthesized by a simple one-step hydrothermal method. The prepared CDs showed superior dispersibility and fluorescence performance compared to the CDs that have been reported for the detection of water content in organic solvents. It can realize the fluorescence detection of trace water in several water-soluble organic solvents such as N,N-dimethylformamide, ethanol and methanol with wide linear range (0 %–100 %) and high sensitivity. This will provide a powerful tool for the rapid detection of water content in organic solvents in chemical production.

Rapid and ultra-sensitive trace water determination in organic solvents utilizing nitrobenzoxadiazole (NBD)-based fluorescent sensing system

The presence of minute quantities of water in organic solvents can affect the progress of many reactions and cause unnecessary losses and even safety accidents in the chemical industry, especially in the productions process of organic fine chemicals. Therefore, it is necessary to carry out high-performance strategies for trace water detections in commonly used organic solvents. In this work, a fluorescent sensing system based on competitive binding of protons has been developed, demonstrating remarkable responses by UV–vis absorption and fluorescence two-modes toward a trace amount of water in organic solvents including 1,4-dioxane (Diox), tetrahydrofuran (THF), acetonitrile (MeCN), acetone (ACE), dimethylsulfoxide (DMSO) and mixed organic solvents (THF: MeCN=1: 1). The key component of the sensing system is a newly designed fluorophore NBD-PMA, which can be deprotonated to form a dynamic non-luminescent adduct, namely NBD-PMA-F, by an organic fluoride salt tetrabutylammonium fluoride (TBAF). NBD-PMA-F can be reprotonated via using trace water, exhibiting fluorescence turn on of the system. The as-prepared sensing system shows superior sensitivity, low detection limits (v/v, 0.0007 %), quick response speed (≤1.2 s) and good reversibility. Moreover, naked-eye visual rapid detection has also been successfully realized at ambient temperature, which demonstrated their practical applications value for trace water determinations.

Propeller shaped triarylamine acid: An ultra-sensitive fluorescence probe for distinguishing propanol isomers and water sensing in organic solvents

The photophysical properties of conformationally flexible (TPA-C) and partially rigidified (Cz-C) triarylamine acids were explored in solid as well as solution state and correlated with the structure. TPA-C and Cz-C exhibited moderate solid-state fluorescence (Φf = 6.2 % (TPA-C) and 5.6 % (Cz-C)) and self-reversible mechanofluorochromism. TPA-C produced fluorescent polymorphs (TPA-C-1 and TPA-C-2) with tunable fluorescence. TPA-C-1 showed unusual carboxylic acid intermolecular interactions whereas TPA-C-2 and Cz-C showed usual carboxylic acid dimer. TPA-C exhibited strong solvent polarity dependent tunable fluorescence (Φf = 0.01 to 0.11 compared to quinine sulphate standard) but Cz-C was non-emissive in the solution state. The dual emissive TPA-C showed highly sensitive fluorescence changes in organic solvents (CH3CN, THF, DMF, EtOH) when trace amount of water was added. In CH3CN, TPA-C showed weak fluorescence at 474 nm and addition of water (1 %) exhibited significant blue shift (λmax = 416 nm). The fluorescence intensity was gradually decreased with blue shifting in DMF, THF and EtOH with water addition. Importantly, TPA-C showed drastically different fluorescence in n-propanol (n-PA) and iso-propanol (IPA). TPA-C in n-PA showed fluorescence at 408 nm that was clearly red shifted to 438 nm with 0.1 % addition of IPA. The limit of detection (LOD) of water in CH3CN, DMF, THF and EtOH by TPA-C revealed 0.02, 0.7, 0.08 and 0.77 %, respectively. The LOD of IPA sensing in n-PA is 0.05 % and indicated the very efficient sensing and distinguishing propanol isomers. Thus, simple triphenylamine acid showed excellent water sensing and propanol isomers discrimination that could be attributed to the twisted intramolecular charge transfer (TICT) formation.

Efficient visible light-driven Photodegradation of malachite green dye using carbon quantum dots-MXene nanocomposite: Synthesis, characterization, and performance evaluation

BackgroundRemoval of azo dyes is one of important issue in water treatment studies and many of research works focused on it. Current work represents a simple and economical feasible to synthesize carbon quantum dots (CQDs) integrated with Ti3C2(OH)2 MXene nanocomposite (CQDs/MXene) for rapid photodegradation of Malachite green (MG) under visible light irradiation. In practice, CQDs were synthesized via a hydrothermal method from Petroselinum crispum leaves, while Ti3C2(OH)2 nanosheets resulted from a simple etching process of Ti3AlC2 using an alkaline solution (KOH with a trace amount of water). MethodsSubsequently, nanocomposites (CQDs/MXene) were prepared by a self-assembly process through sonication-assisted mixing process under ambient conditions. The prepared catalysts were characterized using various analyses like analysis employing field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and an energy dispersion X-ray (EDX) spectrometer to determine the chemical composition. The optimum measurement of this activity of the CQDs/MXene was attained through adjusting several constraints such as pH, dye concentration, amount of temperature and photocatalyst. Significant findingsThe kinetics of the degradation process were represented using the Langmuir–Hinshelwood model, with a rate constant (k) of 0.1382 min−1. This means that the degradation of MG dye follows a first-order reaction with respect to the dye concentration. In addition, the study also looked at the reusability of the prepared CQDs/MXene nanophotocatalyst and found that it exhibited outstanding stability after three reaction cycles. This suggests that the nanophotocatalyst is a promising material for efficient and sustainable degradation of MG dye. The nanocomposite displays high photocatalytic activity with the ability to reduce 96.1 % of the MG dye concentration after being exposed to 25 min of visible light.

Superamphophilic antimicrobial membrane engineered with zinc-coordinated metallo-polymeric framework nanocoating

The combat against contamination by trace amounts of water and bacteria in aviation fuel remains a challenge, necessitating a comprehensive strategy. Here, a superamphophilic antimicrobial membrane is developed by featuring a stable zinc-coordinated polydopamine metallo-polymeric framework (PDA/Zn) on the skeleton of polyethylene terephthalate (PET) non-woven fabric. The formation of the PDA/Zn framework is streamlined through dopamine polymerization synchronized with metallo-ion coordination. This work delves into the intrinsic stability and superamphiphilic properties of the PDA/Zn framework, as well as systematically investigates its performance in fuel dehydration and carbophilus elimination. The resulting membrane exhibits a high gravity-driven flux and achieves a significant reduction in water content to below 10 ppm in aviation fuel, attributed to a demulsification and aggregation mechanism. Furthermore, our findings highlight the nearly complete antibacterial multifunctionality of the proposed membrane. It effectively prevents bacterial attachment at the liquid-solid interface and brings about bacterial eradication through the presence of Zn2+ ions and the mechanical puncturing effect of nanostructure cusps. This work not only advances applications in water dehydration and bacterial elimination but also pioneers opportunities for designing advanced functional membranes with multifaceted functionalities, including anti-fouling, self-cleaning, and antimicrobial properties, setting the stage for broader applications in membrane field.

Exploring the interactions of NH3 and H2O co-condensation: A study on the potential of supersonic separators for NH3–H2 separation

The use of a supersonic separator presents a novel approach for separating ammonia (NH3) from hydrogen (H2). Even trace amounts of water (H2O) can significantly influence the condensation characteristics of NH3. This study presents mathematical models for homogeneous NH3 and H2O condensation and heterogeneous NH3–H2O condensation. Through computational analysis, we revealed that the droplet radius and liquid mass fraction of a single condensable gas condensation increased accordingly with increasing inlet condensable gas content. Interactions between the condensation processes of NH3 and H2O were also captured in the simulation. Notably, at 100 ppm H2O content, H2O spontaneously condensed before NH3, serving as a condensation nucleus for NH3, and the heterogeneous condensation of NH3 decreased the rate of its spontaneous condensation. At an inlet H2O content of 50 ppm, the onset of spontaneous NH3 condensation coincided with that of H2O, with H2O having a negligible effect on NH3 condensation. The impact of H2O on NH3 condensation transitioned from minimal to inhibitory and then to facilitative as the content of H2O increased from 25 ppm to 250 ppm. At the nozzle outlet, the liquid mass fraction of NH3 initially decreased from 0.0414 to 0.0352 and then increased to 0.0446.

Mechanistic Studies on Rhodium-Catalyzed Chemoselective Cycloaddition of Ene-Vinylidenecyclopropanes: Water-Assisted Proton Transfer.

Rhodium-catalyzed cycloaddition reactions are a powerful tool for the construction of polycyclic compounds. Combined experimental and DFT studies were used to investigate the temperature-controlled chemoselectivity of cationic rhodium-catalyzed intramolecular cycloaddition reactions of ene-vinylidenecyclopropanes. After a series of mechanistic studies, it was found that trace amounts of water in the reaction system play an important role in generating the product with endo double bond located on a five-membered ring and revealed that trace amounts of water in the reaction system, including the rhodium catalyst, substrate and solvent, were sufficient to promote the formation of the product with endo double bond located on a five-membered ring, and additional water could not further accelerate the reaction. DFT calculation results show that the addition of water indeed significantly lowers the energy barrier of the proton transfer step, making the formation of the product with endo double bond located on a five-membered ring more likely to occur and confirming the rationality of water-assisted proton transfer occurring in the selective access to the product with endo double bond located on a five-membered ring.

Reversible hydrochromic CsPbBr3/Cs4PbBr6@MCM-41 to enable organic solvent polarity detection

Hydrochromic materials have received much attention in anticounterfeiting due to their reversible photoemission properties toward water. However, existing hydrochromic materials usually suffer from slow hydrochromic response and limited stability, repeatability, and color tunability. This paper found for the first time that CsPbBr3/Cs4PbBr6 composites with quantum-limited domain effects had reversible hydrochromism. CsPbBr3/Cs4PbBr6 composites were successfully synthesized in molecular sieve MCM-41 using an improved mechanochemical method. The composites underwent a reversible phase transition from Cs4PbBr6/CsPbBr3 to CsPbBr3 upon treatment with a trace amount of water, the photoluminescence colors underwent a change from blue to green, and reversion occurred due to heating. Mechanistic investigation revealed that quantum dots underwent soft agglomeration due to van der Waals forces in polar solvent environments, affecting the action of quantum domain-limiting effects. Therefore, organic solvents with different polarities can cause different degrees of reversible discoloration of the material. This study provides new ideas for understanding the phase transition and agglomeration of metal halide perovskite quantum dots in polar solvent environments. Additionally, it offered new options for aqueous color-changing materials and organic solvent polar detection materials.

Water sensitive fluorescence tuning of V-shaped ESIPT fluorophores: Substituent effect and trace amount water sensing in DMSO

Highly sensitive nature of excited state intramolecular proton transfer (ESIPT) functionality in organic fluorophores made them potential candidates for developing environmental sensors and bioimaging applications. Herein, we report the synthesis of V-shaped Dapsone based Schiff base ESIPT derivatives (1–3) and water sensitive wide fluorescence tuning from blue to red in DMSO. Solid-state structural analysis confirmed the V-shaped molecular structure with intramolecular H-bonding and substituent dependent molecular packing in the crystal lattice. 1 showed strong solid-state fluorescence (λmax = 554 nm, Φf = 21.2 %) whereas methoxy substitution (2 and 3) produced tunable but significantly reduced fluorescence (λmax = 547 (2) and 615 nm (3), Φf = 2.1 (2) and 6.5 % (3)). Interestingly, aggregation induced emission (AIE) studies in DMSO-water mixture revealed water sensitive fluorescence tuning. The trace amount of water (less than 1 %) in DMSO converted the non-emissive 1–3 into highly emissive state due to keto tautomer formation. Further increasing water percentage produced deprotonated state of 1–3 in DMSO and enhanced the fluorescence intensity with red shifting of emission peak. At higher water fraction, 1–3 in DMSO produced aggregates and red shifted the emission with reduction of fluorescence intensity. The concentration dependent fluorescence study revealed the very low detection limit of water in DMSO. The limit of detection (LOD) of 1, 2 and 3 were 0.14, 1.04 and 0.65 % of water in DMSO. Hence, simple Schiff bases of 1–3 showed water concentration dependent keto isomer, deprotonated and aggregated state tunable fluorescence in DMSO. Further, scanning electron microscopic (SEM) studies of 1–3 showed water concentration controlled self-assembly and tunable fluorescence.

Hydration MgCl2-NaCl-KCl molten salt using a novel approach for training machine learning potential

The structural information and thermophysical properties of high-temperature magnesium electrolytes play critical roles in controlling the energy consumption of industrial production and the quality of magnesium alloys. Large-scale molecular dynamics simulations can achieve accuracy similar to that of DFT while overcoming the limitations of high-temperature experiments by integrating machine learning (ML) strategies. However, many AIMD simulation tasks, computationally expensive due to configuration and volume optimization, are required to construct an initial dataset for the current ML potential training scheme. To bypass this issue, we developed a novel scheme using Deep Potential to generate ML potential that can be applied to multiple temperatures, improving efficiency without compromising accuracy. A short-time AIMD simulation at a certain target temperature was involved, followed by an iterative task using the DP-GEN package to generate an initial dataset based on a varying upper bound for model force deviation. This dataset was then used in a new DP-GEN task to train ML potential. Our method has been applied for the first time to the molten MgCl2-NaCl-KCl system with trace amounts of water (hydration MNK). The trained potential effectively predicted interatomic energies and forces, with errors of 0.5517 meV/atom and 3.063 meV/Å, respectively, denoting the trained potential is similar accuracy relative to DFT. DPMD simulation, the large-scale methodology, was performed to investigate the structural information and thermophysical properties of the hydration MNK system. Through analyzing the obtained structural information, Coulombic interactions are the dominant forces in the melt and a stronger affinity between Na+ and water molecules relative to other cations. H2O is unable to cross the first coordination layer of Cl-Mg. There are also differences in how the hydrogen and oxygen atoms of the water molecules interact with the cations in the melt. This work discusses the temperature-dependent evolution of several thermophysical properties, including density, self-diffusion coefficient, viscosity, and ionic conductivity. Our results show that density, viscosity, and ionic conductivity all exhibit negative relationships with temperature. In addition, the order of diffusion is as follows: DMg2+<DCl-<DNa+<DK+<DH2O.

Hydration is not detrimental for Glycerol:Lactic acid deep eutectic mixtures

Natural deep eutectic solvents (NADES) have been proposed as eco-friendly alternatives to organic solvents. A trace amount of water is frequently unavoidable as a contaminant and may be also purposely added to the mixtures to reduce their problematically high viscosity and costly price. It is critical to understand the different effects of water on the characteristics of NADES, particularly for their use in procedures such as bioactives’ extraction, and enzymatic synthesis, among others. In this work, the effect of water on the physicochemical properties and structural features of glycerol:lactic acid (GLY:LAC) deep eutectic mixture was investigated. The structural changes after water addition were evaluated using FTIR-ATR and 1H NMR spectroscopy. The pH, conductivity, and polarity of the mixtures were also evaluated after the addition of different percentages of water. Molecular dynamics simulations (MD) were applied to assess the role of water on NADES components' distribution and properties, including the number of hydrogen bonds (HB), the radial distribution functions (RDF), and the spatial distribution functions (SDF). The results demonstrated that when water enters the system, the hydrogen bonds between the eutectic components break but new ones are formed creating strong interactions between them and the water. A ternary eutectic combination arises, leading to a melting point lower than the original counterparts, even with 90 % water, caused by the formation of stronger intermolecular interactions. The MD simulations indicate no phase separation regardless of the ratio of the components or the water content in the mixture, showing preservation of the eutectic behavior.Overall, these unprecedented results, in which the rupture of the HB between eutectic mixtures is never observed up to 90 % water, unravel the potential of these novel mixtures for multiple applications.

Polynitrogen clusters interaction with water: experimental and theoretical perspectives

Polynitrogen clusters are of great interest as potential high-energy-density materials (HEDMs). However, it is still a challenge to effectively manufacture pure nitrogen clusters. Here, we present a method to produce all-nitrogen clusters ranging in size from 3 to 10 using a self-developed apparatus consisting of a laser vaporization cluster source and a mass spectrometer. The results indicate that the mass peak of the N4 + cluster is dominant, and the cooling of the cluster source with liquid nitrogen effectively enhanced the intensities of larger nitrogen clusters. The trace amounts of water in the carrier gas affects the relative signal intensities of nitrogen clusters, suggesting that water molecules can affect their stabilities. The geometrical structures of the N(n = 3–10) clusters are determined by CALYPSO cluster structural search method and density functional theory calculations. A series of promising polynitrogen clusters, such as Z-shaped N clusters and bicyclic N clusters, are identified. The molecular dynamics simulations indicate the decomposition energy barrier of (N4–H2O)+ cluster is lower than that of N4 + cluster by 2.3 kcal mol−1, while the decomposition energy barrier of (N8–H2O)+ cluster is higher than that of N8 + cluster by 1.4 kcal mol−1. These findings provide useful information for the generation and stabilization of polynitrogen clusters, which are valuable for the design and synthesis of HEDMs.

Anchoring Bi2S3 quantum dots on flower-like TiO2 nanostructures to boost photoredox coupling of H2 evolution and oxidative organic transformation

The rational integration of semiconductor quantum dots (QDs) with anatase TiO2 nanostructures is a promising strategy to develop efficient photocatalysts. Herein, Bi2S3QD/TiO2 photocatalyst was constructed by controllably depositing Bi2S3 QDs on flower-like TiO2 nanostructures and used for the photocatalytic redox-coupling reaction of H2 evolution and oxidative transformation of benzyl alcohol. The abundant amino groups in TiO2 nanostructures served as the anchoring sites for uniform growth of Bi2S3 QDs. The anchoring of Bi2S3 QDs onto TiO2 nanostructures not only enhanced the photoabsorption ability and the photogenerated charge separation efficiency but also afforded powerful photogenerated charge carriers and abundant active sites for the photocatalytic reaction. As a result, the Bi2S3QD/TiO2 photocatalyst exhibited a favorable performance in the redox-coupling reaction, providing the high production rates of H2 up to 4.75 mmol·gcat−1·h−1 and benzaldehyde up to 6.12 mmol·gcat−1·h−1, respectively, as well as an excellent stability in the long-term photocatalytic reaction. Meanwhile, a trace amount of water in the reaction system could act as a promoter to accelerate the photocatalytic redox-coupling reaction. The photocatalytic mechanism following S-scheme heterojunction was proposed according to the systematic characterizations and experimental results. This work offers some insight into the rational construction of efficient and cost-effective photocatalysts for the conversion of solar to chemical energy.

Fluoride Induced Dual Mode Moisture Detection in Organic Solvents, Food, and Agricultural Materials using Benzothiazole Based Azo Dye Sensor

AbstractMoisture detection through naked eye is important in various fields, including pharmaceuticals, fuels, materials, and agriculture. In this study, we demonstrate the use of a strategically designed organic molecule, 2AMBP, for the detection of moisture in organic solvents and real‐life samples. The principle behind this sensory system involves fluoride‐induced deprotonation followed by water‐induced re‐protonation. The deprotonated form of 2AMBP displays a color‐changing response (yellow to pink) even in trace amounts of water (LOD: 0.0207 % by spectrophotometric analysis), making it a highly sensitive probe for detecting moisture. We show that the anionic receptor moieties of 2AMBP can be employed for the quantification of water impurity in various real‐life samples, and we develop inexpensive, reusable, dye‐coated paper sensor for quick onsite moisture detection and quantification. Interestingly, a smart phone camera can be used to provide relative RGB values that directly correlate to the amount of moisture present in the sample. The 2AMBP‐F‐ exhibits significant changes in fluorescence properties in the presence and absence of water, which makes it an effective fluorescent switch for detecting moisture. Overall, 2AMBP is a highly sensitive, sustainable material that can be conveniently used by laymen for moisture detection without the need for specific instruments or expertise.

Role of decomposition products in the oxidation of cyclohexene using a manganese(III) complex

Metal complexes are extensively explored as catalysts for oxidation reactions; molecular-based mechanisms are usually proposed for such reactions. However, the roles of the decomposition products of these materials in the catalytic process have yet to be considered for these reactions. Herein, the cyclohexene oxidation in the presence of manganese(III) 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine chloride tetrakis(methochloride) (1) in a heterogeneous system via loading the complex on an SBA-15 substrate is performed as a study case. A molecular-based mechanism is usually suggested for such a metal complex. Herein, 1 was selected and investigated under the oxidation reaction by iodosylbenzene or (diacetoxyiodo)benzene (PhI(OAc)2). In addition to 1, at least one of the decomposition products of 1 formed during the oxidation reaction could be considered a candidate to catalyze the reaction. First-principles calculations show that Mn dissolution is energetically feasible in the presence of iodosylbenzene and trace amounts of water.

Regulating side chain of flexible polyacrylate resins for efficient removal of trace dissolved organics with moderate polarity

Efficient removal of trace amounts of dissolved organics with moderate polarity (DOMP) in water via adsorption method is a challenge. Most typical adsorption materials such as activated carbon exhibits poor selectivity and few polymers can remove DOMP in water. Herein, four polyacrylate resin (PAR)-based materials with different side chain are successfully fabricated, which can selectively adsorb pure organics with moderate polarity (dielectric constant ranging from 2.21 to 21). Interestingly, PARs can also selectively remove low concentration of toluene (5 ppm) and chloroform (1 ppm) in water with maximum removal efficiencies of 98.16% and 95.65%, respectively. Molecular dynamic (MD) simulations reveals that the driving force and selectivity of the adsorption behaviors can be attributed to the van der Waals interactions between the side chain of PARs and organics. Our study provides a designing strategy and novel material for efficient removal of organic pollutants with trace amounts in water.

Redox‐Independent Low Water Solubility in Quartz and Implications for Water Storage in the Crust

AbstractQuartz is an important mineral constituent of the continental crust, which commonly contains trace amounts of water as hydroxyl in the lattice. Despite considerable efforts to document the roles of pressure, temperature, and chemistry on water storage in quartz, the effect of redox state, a key thermodynamic factor in Earth sciences, has not been well established. We assessed the redox effect on water solubility in quartz at 2 and 10 kbar and 800°C, by equilibrating two natural gem‐quality crystals with water over a range of redox conditions. Recovered samples show infrared absorption bands at 3,100–3,600 cm−1. Dehydration experiments at 1200°C (room pressure) suggest that the two bands at ∼3,197 and 3,293 cm−1 are linked to Si‐O overtones, with the other bands to hydroxyl. The water solubility, ∼3.7–32.2 ppm wt. H2O, is redox‐independent, differing from other minerals such as feldspar, pyroxenes, garnet, rutile, and olivine in which the water solubility is significantly redox‐dependent. This provides evidence that the water incorporation in quartz is not controlled by polyvalent elements and/or other redox‐linked mechanisms. Considering the roles of Al, Li, and B in incorporating water and its low solubility over remarkable variations in the abundances of those elements in most natural samples, quartz is not a major water carrier compared to other nominally anhydrous minerals (NAMs) in the crust. The partitioning of water between quartz and other crustal NAMs such as feldspar, pyroxenes, rutile, and garnet is redox‐influenced, and is unlikely to be constant in the crust.

Aqueous Solid Formation Kinetics in High-Pressure Methane at Trace Water Concentrations.

Natural gas containing trace amounts of water is frequently liquefied at conditions where aqueous solids are thermodynamically stable. However, no data are available to describe the kinetics of aqueous solid formation at these conditions. Here, we present experimental measurements of both solid formation kinetics and solid-fluid equilibrium for trace concentrations of (12 ± 0.7) ppm water in methane using a stirred, high-pressure apparatus and visual microscopy. Along isochoric pathways with cooling rates around 1 K·min-1, micron-scale aqueous solids were observed to form at subcoolings of (0.3-8.6) K, relative to an average equilibrium melting temperature of (253 ± 1.9) K at (8.9 ± 0.08) MPa; these data are consistent with predicted methane hydrate dissociation conditions within the uncertainty of both the experiment and model. The 36 measured formation events were used to construct a cumulative formation probability distribution, which was then fitted with a model from Classical Nucleation Theory, enabling the extraction of kinetic and thermodynamic nucleation parameters. While the resulting nucleation parameter values were comparable to those published for methane hydrate formation in bulk-water systems, the observed growth kinetics were distinctly different with only a small percentage of the water in the system converting into micron-scale solids over the experimental time scale. These results may help explain how cryogenic heat exchangers in liquefied natural gas facilities can operate for long periods without blockages forming despite being at very high subcoolings for aqueous solids.

Effect of Flow on the Corrosion Behavior of Pipeline Steel in Supercritical CO2 Environments with Impurities

Corrosion is a major concern in transmission pipelines that transport captured CO2. While dry CO2 is noncorrosive, significant corrosion has been reported in dense-phase CO2 with trace amounts of water and impurities such as O2, H2S, SOx, and NOx. The aim of this work is to improve our understanding of the physicochemical aspects of the corrosion of carbon steels in the high-pressure environments associated with CO2 transmission pipelines. The effect of flow on the corrosion of X65 carbon steel was investigated in a series of autoclave tests with different combinations of impurity concentrations in supercritical CO2 conditions (8 MPa and 35°C). The corrosion rate of specimens was determined by weight loss measurements. The surface morphology and composition of the corrosion product layers were characterized using surface analytical techniques (scanning electron microscopy, eneregy dispersive x-ray spectroscopy, and Raman microscopy). Localized corrosion was measured via surface profilometry after corrosion products were removed. Results showed that no corrosion was observed in the supercritical CO2 with 650 ppmv of water, 50 ppmv SO2, and 100 ppmv NO, but corrosion occurred when SO2 concentration was increased to 4,500 ppmv and 40,000 ppmv of O2 was added to the system. The presence of flow significantly accelerated the corrosion of carbon steel. Furthermore, localized corrosion was observed in the presence of both O2 and flow.

Water Increases the Faradaic Selectivity of Li-Mediated Nitrogen Reduction.

The lithium-mediated system catalyzes nitrogen to ammonia under ambient conditions. Herein we discover that trace amount of water as an electrolyte additive-in contrast to prior reports from the literature-can effect a dramatic improvement in the Faradaic selectivity of N2 reduction to NH3. We report that an optimal water concentration of 35.9 mM and LiClO4 salt concentration of 0.8 M allows a Faradaic efficiency up to 27.9 ± 2.5% at ambient pressure. We attribute the increase in Faradaic efficiency to the incorporation of Li2O in the solid electrolyte interphase, as suggested by our X-ray photoelectron spectroscopy measurements. Our results highlight the extreme sensitivity of lithium-mediated N2 reduction to small changes in the experimental conditions.