Amine Systems Research Articles

Bio-thymol containing new high-performance thymolphthalein based polybenzoxazine: Thermal, superhydrophobic and dielectric properties

An increase of global population and consequent cause of environmental concerns, significant efforts have been made to reducing the use of fossil-based precursors and chemicals. The sustainable bio-benzoxazine resins were prepared using thymolphthalein and different amines systems such as aliphatic amines [butylamine (ba), hexylamine (ha), 2-ethylhexylamine (eha), dodecylamine (dda), octadecylamine (oda)), aryl amines (aniline (a), 4-fluoroaniline (fa), 3-trifluoromethylaniline (tfma)], and miscellaneous amines [cyclohexyamine (cha), allylamine (aa) and furfurylamine (ffa)] with paraformaldehyde through Mannich condensation. The molecular structure of corresponding benzoxazines was analysed using FTIR and 1H NMR spectroscopic techniques. Superhydrophobic cotton cloth was prepared using aliphatic amine based benzoxazine coating. The reinforcements bio-silica from bamboo ash and graphitic carbon nitride (GCN) from melamine precursors were separately prepared and functionalized under appropriate experimental conditions, which are used as reinforcement for the development of polybenzoxazine composites. Thermal stability, morphology and hydrophobicity of cardanol functionalized-GCN and GPTMS functionalized bio-silica reinforced polybenzoxazine composites were studied using TGA, FESEM and goniometer respectively. The poly(THP-oda) coated cotton fabric possesses the value of highest water contact angle of 154°. Further the poly(THP-oda) coated cotton fabric was tested for its efficiency towards oil-water separation. The value of dielectric constant of 15 wt% of bamboo ash silica reinforced poly(THP-ffa) and 15 wt% of C-GCN reinforced poly(THP-tfma) are 1.9 and 7.9 respectively.

Cascade Reaction with Preservation of Stereochemistry for the Synthesis of Fused Cyclic Amine Systems

Key words Mannich reaction - aza-Cope reaction - piperidines - cascade reaction

Flotation Mechanism of Sphalerite by Sulfuration–Amine Method

Sphalerite is a common sulfide mineral, and xanthate is usually used as the collector of sphalerite flotation. In order to realize the simultaneous flotation of sphalerite- and zinc-containing oxide ores, in this paper, dodecylamine was used as the collector and sodium sulfide as the regulator to explore the flotation behavior of sphalerite in a sulfuration–amine system through single mineral flotation tests, and several analytical methods, including contact angle measurement, adsorption capacity test, FT-IR, and XPS, were employed to discuss the interaction mechanism of dodecylamine on the surface of sphalerite. The results confirm that dodecylamine had a strong collecting effect on sphalerite throughout almost the entire pH range, and the flotation recovery increased with the increase in pH, reaching 86.81% at pH 12. It was found that the effect of sodium sulfide on the floatability of sphalerite was relatively weak, and a weak activation effect, of about 2% improved recovery, was achieved. The results of the mechanism analysis further show that dodecylamine underwent both physical adsorption and chemical adsorption on the surface of sphalerite, and the physical adsorption was enhanced with the increase in pH. The above findings provide evidence for the simultaneous flotation of zinc-containing sulfide-oxide mixed minerals.

Engineering pKa value of 3° amine for enhanced production of dialkyl carbonate via Se-catalyzed oxidative carbonylation

C1 chemistry plays a vital role in the chemical and energy industry in terms of recycling C1 molecules and high productivity. As one of the C1 chemistry reactions, oxidative carbonylation of alcohols to corresponding dialkyl carbonates (DACs) has been studied but still has problems with catalysts in terms of corrosion and low yield of DACs. To address this issue, various Se/Ph2Se2/tertiary amine catalytic systems were applied to the oxidative carbonylation of alcohols to produce DACs, and Se/Ph2Se2/DMAP showed higher catalytic activity [60.9% yield of bis(2-methoxyethyl) carbonate (BMEC) at a turnover frequency (TOF) value = 32.5 h−1] compared to other tertiary amines (TAs) systems in the oxidative carbonylation of 2-methoxyethanol (MEG). Moreover, with this catalytic system, the oxidative carbonylation of C1–C4 n-alcohols yielded over 40% of DACs with high TOF value (over 40 h−1), which are unprecedented catalytic activity in terms of both yield and TOF value, compared with previous reports. We also found a relationship between the hydrogen bond (HB) strength of alcohol···TA and the catalytic performances. Additionally, the catalytic activity with pKa of TA showed volcano-type correlation. Finally, we investigated the role of TA and proposed a plausible mechanism based on 1H NMR study and the aforementioned correlations.

Influence of Water on an Epoxy/Amine-Metal Interphase: A Combined DFT and Mixing Calorimetry Approach.

Epoxy-amine systems are ubiquitous in the field of industrial thermosetting polymers, often used in a moist atmosphere. In addition, previous studies showed amine-metal interactions through the formation of an interphase, with the formation of surface complexes that may involve the formation of water molecules. However, to date, the impact of water on an epoxy/amine-metal interphase has not been specifically addressed. In this work, we examined for the first time the role of this potential fourth component by way of a dual experimental/computational approach. The effect of water on the glass-transition temperature of the obtained polymers was quantified. The in situ formation of a DETA-Al-water interphase was followed by mixing calorimetry. The DETA-water interaction was highly exothermic, and the underlying mechanism was discussed on the basis of DETA hydration, which was confirmed by density functional theory (DFT) and Monte Carlo simulations. Taking into account the pre-existing interaction between diethylenetriamine (DETA) molecules allowed us to model all experimental data. Comparison of experimental and calculated IR spectra contributed to validate the simulation parameters used. Our findings indicate that the presence of water may noticeably affect epoxy-amine-based systems. Mixing calorimetry and computational modeling appear as particularly adapted tools for the comprehension of such complex systems.

Natural attapulgite supported nano-Ni catalysts for the efficient reductive amination of biomass-derived aldehydes and ketones

The efficient synthesis of useful primary amines via reductive amination of biomass-based aldehydes and ketones over earth-abundant base metal catalysts is an attractive biomass value-adding technology yet facing lots of challenges. Herein, natural attapulgite (ATP) was applied as support for the fabrication of active Ni catalysts with different Ni loadings (5–30 ​wt%) by the deposition-precipitation method. The Ni/ATP-550 catalyst with 10–15 ​wt% Ni loadings was found to present the highest catalytic performance for the synthesis of valuable 5-amino-1-pentanol (5-AP) via reductive amination of biofurfural-derived 2-hydroxytetrahydropyran among a variety of commonly used oxide supports loaded Ni catalysts, as well as ATP supported nickel catalysts with other loadings, achieving 5-AP yield up to 94%. The intrinsic activity of the Ni/ATP catalysts was found to depend strongly on the Ni0 crystallite size and Ni0 fraction of the catalysts, which generally increased with increasing Ni0 crystallite size and fraction, owing probably to the hydrogenation of imine intermediate is a structure-sensitive reaction. The efficient 10Ni/ATP-550 catalyst also exhibited good activity and stability in the reductive amination of several other biomass-derived aldehydes and ketones to their corresponding primary amines with good to excellent yields (81%–99%). This work provided a clean and efficient natural ATP-supported non-noble metal nickel-based catalytic system for the reductive amination of aldehydes and ketones to synthesize high-value-added primary amines, which could be a promising candidate for the industrial production of amines.

Analysis of Immunobiochemical Parameters in Overweight People in Assessing the Risk of Cardiovascular Diseases

A comparative analysis of specific immunobiochemical parameters, including natural antibodies (NAb) to endogenous regulators of the cardiovascular system, adrenal and gastrointestinal hormones, was performed in students aged 18-22 years with normal and increased body weight (the body mass index from 18.5 to 24.9 kg/m2 and from 25 to 29.9 kg/m2, respectively). The serum content of NAb and hormones was determined by ELISA. The level of the studied indicators depended on the body mass index value. In overweight subjects, the main immune indicators of the biogenic amine system, renin-angiotensin system, and kinin system exceeded the normal. The cortisol level was higher than in subjects with normal body weight. Aldosterone secretion was less dependent on the ACTH content and was lower than in students with normal body weight. The content of cholecystokinin and gastrin corresponded to the values for overweight. These trends in hormone contents are a predisposing factor for further weight gain. Practical significance of the combined assessment of disturbances in the immunological and biochemical homeostasis has been established. Analysis of the adrenal and gastrointestinal hormones can predict the risk of weight gain, but at the same time, changes in the level of immunological indicators in subjects with increased body weight characterizes the possibility of developing cardiovascular pathologies.

Gas absorption in reactive solutions: Adapted instrumentation of a stirred cell for kinetic study and application to CO2/amine systems

The elimination of impurities from natural gas (water, CO2, H2S, mercaptans) is an obligation: in Europe, a max. of 20 mg/Sm3 in total sulfur (at 15°C and 1 atm) is allowed, as well as 2.5 vol% in CO2. It maximizes the calorific value of delivered gas and limits chemical risks (corrosion, toxicity) associated with this transition fuel to cleaner energy sources. Acid gas separation is commonly performed by reactive gas-liquid absorption. Raw gas and absorptive solution are brought into counter current contact in an absorber at 40-80°C and 30-80 bar. Then the acid-gas loaded solvent is sent to a stripper where acid gas desorption from the solvent takes place at T between 105 and 140°C and P ≤ 2.5 bar. The solvent is an aqueous base (e.g., amine) solution. A good solvent has a high reactivity with the dissolved gas during absorption and a low regeneration energy, hence the advantage of mixtures of two amines. Here we study an aqueous solution of a small amount of piperazine (PZ) added to methyldiethanolamine (MDEA). PZ reacts faster with CO2 than MDEA, and the major reaction product with CO2 is the hydrogen carbonate ion HCO3-, which lowers the solvent regeneration duty. This work aims at characterising the kinetics of the absorption of CO2 in an aqueous solution of MDEA-PZ. Indeed, no consensus has been found on the reaction mechanism of CO2 in this amine mixture; the synergies between MDEA and PZ observed in the literature remain poorly explained. However, its knowledge is essential to optimize solvent formulation and industrial unit design.

Single-atom solutions promote carbon dioxide capture

Single-atom solutions are proposed to promote CO2 capture for carbon neutralization. Copper, iron, manganese and boron based single-atom DMF solution along with iron and manganese based single-atom ethanol solution are developed scientifically. The DFT simulation and experiment are performed to analyze the system of single-atom solution and CO2. It is shown that copper, iron and boron single atoms promote the solution to absorb carbon dioxide. Manganese single atom shows little intensification effect for carbon dioxide absorption. More importantly, copper single atom also promotes CO2 desorption at low temperatures. Based on the interaction energy and desorption energy barrier, it is concluded that copper and boron based single-atom solutions show outstanding CO2 capture performance. Their CO2 desorption energy were assessed as 1.65 GJ/t CO2 and 0.97 GJ/t CO2, which are 56.58% and 74.47% lower than the conventional amine system.

Experimental method and mathematical method for VLE plots in 3DMA1P-CO2-H2O system

The concentration profiles of all chemicals obtained in the Amine-CO2-H2O system based on the Vapor-liquid equilibrium (VLE) plots are essential for the analysis and understanding of the kinetics. This work aims at obtaining accurate and reliable VLE plots of 3DMA1P via both experimental and mathematical methods. VLE plots are essential for understanding the reaction process and mechanism of carbon dioxide absorption into amine solutions. The experiments were conducted over a concentration range of 1 ∼ 2 mol/L, temperature of 298 K, and CO2 partial pressure of 15 kPa. Regarding the experimental method, 13C NMR detection was performed to generate concentrations of Amine and AmineH+ based on the protonation calibration equation. The results showed that the 13C NMR method had little difference between the results of mass conservation calculation and charge conservation calculation under different CO2 loading. Among the mathematical methods, the results obtained by the pH method involving charge conservation were quite different from those calculated by mass conservation, while the D-M model method strictly following the theoretical system satisfied both the mass and charge conservation. The distribution curves of the concentration of each species obtained by the three methods were compared. It was found that 13C NMR and D-M model method could secure closer and more accurate results than the pH method. In conclusion, both the 13C NMR method and the D-M model method plots are useful for obtaining accurate and reliable VLE plots for the 3DMA1P-CO2-H2O system, as well as for other monoamine and mixed amine systems.

Failure analysis of glass fiber reinforced composite pipe for high pressure sewage transport

The research was conducted on failed GFRP pipes used in sour oilfield gathering and transportation pipelines, with the matrix material being an epoxy resin of an aromatic amine system that destructively cracked after 15 years of operation. To determine the cause of the failure, the failure area of the GFRP pipe was compared to the undamaged area, and the pipe's micro-morphological structure, chemical composition, and mechanical properties were examined. The results show that there are cavity defects in the GFRP pipe with insufficient air bubbles and resin filling, that the overall resin content of the pipe is low, that the curing degree of the outer layer of the damaged area (DA-OL) is severely insufficient, and that the fiber bonding strength is weak. The degradation of the amine curing agent in the outer layer of the pipeline and the oxidative decomposition of the resin were characterized using Fourier transform infrared spectroscopy and X-ray electron spectroscopy, and an irreversible chemical degradation process occurred, reducing the performance of the fiber–matrix interface. The data from nanoindentation and dynamic thermomechanical characteristics confirmed the obvious reduction of nano-hardness and elastic modulus in the outer layer of GFRP tubes. The failure of the pipeline is caused by the interaction of the above factors.

Impact of Solvent on the Thermal Stability of Amines.

Water-lean solvents have been proposed as a possible alternative to aqueous amine systems in postcombustion carbon capture. There is however little data available on how amine degradation is affected by different solvents. This study presents new insights on the effect of solvent on thermal degradation of alkanolamines from laboratory-scale degradation experiments. Replacing the water in aqueous monoethanolamine (MEA) solutions with organic diluents resulted in varying thermal degradation rates. Overall, all tested organic diluents (triethylene glycol, diethylene glycol, mono ethylene glycol, tetrahydrofurfuryl alcohol, N-formyl morpholine/water, and N-methyl-2-pyrrolidone) resulted in higher thermal degradation rates for loaded MEA. None of the proposed parameters, such as acid-base behavior, polarity, or relative permittivities, stood out as single contributing factors for the variation in degradation rates. The typical degradation compounds observed for an aqueous MEA solvent were also observed for MEA in various concentrations and with various organic diluents.

Dinuclear Copper(I) Complexes Supported by Bis‐Tridentate N‐Donor‐Ligands: Turning‐On Tyrosinase Activity

AbstractFour structurally related bis‐tridentate N‐donor ligands with either two secondary amine or two imine functions were synthesized, and the corresponding dicopper(I) complexes were investigated as catalysts for the tyrosinase‐like conversion of 2,4‐di‐tert‐butylphenol (DTBP‐H) to 3,5‐di‐tert‐butylquinone (DTBQ). Notably, the imine systems show evidence for both a μ‐η2 : η2‐peroxo‐dicopper(II) species and catalytic conversion of DTBP‐H to DTBQ. Moreover, kinetic studies indicate that a dinuclear copper‐oxygen species is involved in the monooxygenation of DTBP‐H. In contrast, the amine systems do not show monooxygenase activity. Comparison of the experimentally determined catalytic activities with DFT‐optimized geometries of μ‐η2 : η2‐peroxo‐dicopper(II) intermediates suggests that the ligand rigidity of the imine systems allows equatorial attack of the substrate and, thus, subsequent monooxygenation whereas this is not possible in the amine systems due to the fact that no free equatorial positions are available in the μ‐peroxo intermediate.

Effects of photoinitiators on dental composite resins: a narrative review

In recent years, the components of dental composites have changed in an attempt to improve their biomechanical and chemical properties. Therefore, dentistry contains many different photoinitiator systems, the most common being the binary camphorquinone and tertiary amine system, and most dental light curing agents are designed to suit the camphorquinone (CQ) absorption range. The alternation of the photoinitiator can cause changes in the values of biomechanical properties, such as degree of conversion, hardness, and biocompatibility. This review contains a comparison of the biomechanical properties of dental composites including different photosensitizers, among others: camphorquinone, phenanthrenequinone, benzophenone, and 1-phenyl-1,2 propanedione, trimethyl benzoyl-diphenylphosphine oxide, benzoyl peroxide. The literature reviews used and the observation of randomized studies were from the Bireme, PubMed, SciElo, and LILACS databases from 2008 to February 2021. Objective: To present the action of light-curing agents in composite resin and their mechanical characteristics concluded that the market is constantly evolving related to photoinitiators.

Hydrogen-powered Electrochemically-driven CO2 Removal from Air Containing 400 to 5000 ppm CO2

The performance of a hydrogen-powered, electrochemically-driven CO2 separator (EDCS) was demonstrated at cathode inlet CO2 concentrations from 400 ppm to 5,000 ppm. The impact of current density and CO2 concentration were evaluated to predict operating windows for various applications. The single-cell data was used to scale a 100 cm2, multi-cell stack using a shorted-membrane design for four applications: direct air capture (DAC), hydroxide exchange membrane fuel cell (HEMFC) air pretreatment, submarine life support, and space habitation. For DAC, a 339-cell EDCS stack (7.7 L, 17 kg) was projected to remove 1 tonne CO2 per year. The addition of the EDCS in HEMFC systems would result in nearly a 30% increase in volume, and therefore further improvements in performance would be necessary. A module containing five 338-cell EDCS stacks (38 L, 85 kg) in parallel can support a 150 person crew at 2.1% of the volume of the liquid amine system employed in submarines. For space habitation, a 109-cell EDCS stack (3.2 L, 10 kg) is adequate for 6 crewmembers, and is less than 1% the size and 5% the weight of the current CO2 removal system installed on the International Space Station.

Sensory Gating in TAAR1 Knockout Mice

Trace amines (TA) are a family of endogenous compounds structurallysimilar to classical biogenic amines that may be involved in thepathogenesis of a number of neuropsychiatric disorders. One of themost studied and perspective member of the TA associated receptors (TAARs)family is the TAAR1. The aim of the present study was to investigatethe sensory gating (SG) in freely moving TAAR1 knockout mice ina chronic experiment. The study of SG was conducted in the paired-clickparadigm. The SG indices were calculated as an absolute value by subtractingthe second stimulus response amplitude from the first stimulus responseamplitude (S1–S2) and as a relative value calculated by dividingthe S2 amplitude by the response amplitude on S1 (S2/S1). As a result,a significant decrease in the amplitude of the N40 component wasfound in TAAR1 knockout mice compared to wild-type mice. In addition,the absolute value of sensory gating calculated by the S1–S2 methodwas also reduced, but the relative value of sensory gating denotedas S1/S2 ratio remained unchanged. Thus, the data obtained indicatethe involvement of TAAR1 in the generation of auditory evoked potentialsand the potential involvement of the trace amine system in the dosingand filtering of sensory information.

Enrichment in CO2 Absorption by 2-Methyl Piperazine-Activated Tertiary Amines, Physical Solvents, and Ionic Liquid Systems.

One of the ever-demanding research fields is the development of new solvents with better properties for mitigation of CO2 compared to existing solvents. This work reports the measurement and modeling of CO2 solubility in newly proposed aqueous solvent blends of 2-methyl piperazine with N-methyldiethanolamine (MDEA), sulfolane (TMSO2), and 1-butyl-3-methyl-imidazolium acetate ([bmim] [Ac]). The operating temperature and CO2 partial pressure conditions chosen were 303.2–323.2 K and 2–370 kPa, respectively. Along with this, qualitative 13C NMR and FTIR analysis were also performed to consider the proposed reaction scheme. The experimental vapor–liquid equilibrium data were modeled by a modified Kent–Eisenberg equilibrium model. The equilibrium constants associated with 2-methyl piperazine (2-MPZ) and [bmim] [Ac] deprotonation and carbamate formation reactions were regressed to fit the experimental CO2 solubility data. In addition, the CO2 cyclic capacity and heat of absorption were evaluated for the aq (MDEA + 2-MPZ) blend.

Electrochemical and light-driven CO2 reduction by amine-functionalized rhenium catalysts: A comparison between primary and tertiary amine substitutions

Properly positioned second-coordination sphere functional groups can play an integral role in enhancing catalytic activity, altering product selectivity, and/or reducing the energy cost for desired chemical transformations. In this context, we have investigated the effect of second-sphere tertiary amine groups in the fac-Re(bpy)(CO)3Cl (ReBpy) catalyst scaffold (bpy is 2,2′-bipyridine). A family of isomeric Re(bpy) catalysts bearing N,N-dimethylaniline (DMA) substituents at the 6 position of 2,2′-bipyridine has been synthesized and characterized, where the -NMe2 group of each complex is installed at the ortho, meta, or para position of the pendant phenyl ring to systematically vary the distance between the amine and the rhenium metal center. The para-substituted complex (Re-pNMe2) leads the series with the highest turnover frequency (168 s−1) and highest turnover number (80) measured under optimized electrochemical and photochemical conditions, respectively. Spectroelectrochemical experiments were performed to identify reduced intermediates that are involved in the catalytic cycles of these complexes. In addition, the catalytic parameters have been compared with the analogous and previously reported series of Re catalysts bearing –NH2 functionality in the second-coordination sphere. Our results demonstrate that, unlike the aniline-substituted primary amine systems, catalysis with the DMA-substituted tertiary amine complexes is predominantly governed by inductive electronic effects.

Phase Splitting Rules of the Primary/Secondary Amine–Tertiary Amine Systems: Experimental Rapid Screening and Corrected Quasi-Activity Coefficient Model

Phase Splitting Rules of the Primary/Secondary Amine–Tertiary Amine Systems: Experimental Rapid Screening and Corrected Quasi-Activity Coefficient Model

Reduced energy consumption and enhanced CO2 desorption performance of non-aqueous ionic-liquid-containing amine blends with zeolites

Excessive emissions of carbon dioxide (CO2), a primary greenhouse gas, can cause serious environmental concerns, such as climate change and global warming. Therefore, carbon capture, utilization, and storage (CCUS) strategies are crucial for reducing the globalcarbon footprint. However,the considerable energy penalty in the regeneration of CO2-loaded solutions is a critical challenge encountered in the industrial application of amine-based post-combustion CO2 capture technology. Therefore, an alternative pathway involving the use of zeolite catalysts was demonstrated in this study to decrease the energy requirement. The regeneration behavior of two different amine systems, namely monoethanolamine (MEA; 5 M)-1-hexanol and MEA (4 M)-1-butyl-3-methylimidazolium acetate (1 M) ([bmim][Ac])–hexanol, with three different modified zeolites (HZSM-5, H-ferrierite (FER), and H-mordenite (MOR)) were studied. The results revealed that the catalyst enhanced the CO2 desorption performance of the non-aqueous hybrid system and reduced the relative energy consumption compared to those of the catalyst-free runs. The zeolite-enabled enhancements of the desorption performance of the rich MEA-hexanol solvent were ordered as follows: HZSM-5 > FER > MOR. HZSM-5 showed a higher catalytic performance than that of FER and MOR, and reduced the heat duty by ∼ 45% compared with that of the catalyst-free test. The zeolite catalysts decreased the desorption time for the regeneration of rich non-aqueous solutions by 25%–30% compared to that of the blank run. In summary, the results contribute toward a comprehensive understanding of the combination of non-aqueous amine blends and zeolite catalysts as an energy-efficient strategy for decreasing the energy consumed during regeneration.