Amine Carbamate Research Articles

Pilot test of water-lean solvent of 2-(ethylamino) ethanol, 1-methyl-2-pyrrolidinone, and water for post-combustion CO2 capture

Water-lean solvent for post-combustion CO2 capture is promising to significantly reduce regeneration energy. It hasn’t been put into commercial application due to unsolved challenges including water balance issue, increased viscosity, and high volatility. Even though numerous water-lean solvents were developed in laboratory, rare of them were tested in pilot scale. Water-lean solvent of 2-(ethylamino) ethanol (EMEA) dissolving into 1-methyl-2-pyrrolidinone (NMP) and water was tested in a CO2 capture pilot with flue gas rate of 280 m3/h. Effects of liquid/gas ratio and reboiler steam rate on CO2 removal efficiency, regeneration energy, lean/rich heat exchanger performance, and volatile amine emission were investigated. Water-lean EMEA achieved CO2 removal efficiency greater than 90 % and the lowest regeneration energy of 2.3 GJ/tCO2, which is 43 % lower than that of 5 M MEA. Water-lean EMEA showed significantly reduced latent heat, greater CO2 capacity, and lower reaction heat (secondary amino) than aqueous MEA and amine blends. It was found that water-lean EMEA regeneration in stripper had extremely lower lean loading (0.1–0.5 mol CO2/L) than aqueous MEA and amine blends, which enables a faster CO2 absorption rate in absorber and a greater CO2 capacity, but also causes larger volatile amine emission. Volatile amine emission after water wash was 110–380 mg/m3. 13C NMR spectrum suggested amine carbamate dominated CO2 absorption products. Due to that increased viscosity decreases heat transfer coefficient (h), lean/rich heat exchanger temperature difference (ΔT) for water-lean EMEA (6.5–7.5℃) was greater than MEA (3.5-5℃) and amine blends (5-6℃), yet smaller than biphasic solvent (8-9℃). A negative power (-0.614) function relation between h and viscosity was fitted and can be further used to normalize sensible heat.

CeO2-catalyzed transformation of various amine carbamates into organic urea derivatives in corresponding amine solvent

A new catalytic system for the direct conversion of various amine carbamates into urea derivatives was devised by combining corresponding amine solvents with CeO2 catalyst. The amine solvents suppressed undesired thermal decomposition of amine carbamates, resulting in the high-yielding production of urea derivatives with high turnover frequency (TOF). One of the reactions demonstrated here was the conversion of ethylenediamine carbamate (EDA-CA) in an ethylenediamine (EDA) solvent. This system produced 2-imidazolidinone (62% yield) and N,N’-bis(2-aminoethyl)urea (38% yield, including its related compounds). The TOF based on the catalyst amount for the EDA-CA transformation was 3.7 h−1, which was at least 6-fold higher than those in previously reported systems operated in different organic solvents at similar reaction temperatures. In the presence of water additive, this catalytic system relying on the CeO2 catalyst and EDA solvent became slower than the reaction without water additive but could still produce the urea derivatives in high yields.

Direct CO2 air capture with aqueous 2-(ethylamino)ethanol and 2-(2-aminoethoxy)ethanol: 13C NMR speciation of the absorbed solutions and study of the sorbent regeneration improved by a transition metal oxide catalyst

The removal of CO2 from the atmosphere (DAC technology) has been accomplished at room temperature and pressure with aqueous solutions of 2-(ethylamino)ethanol (EMEA) and 2-(2-aminoethoxy)ethanol (DGA). The absorption efficiency of the sorbents has been investigated in five cycling steps of absorption-desorption, and the speciation of the solutions has been studied by 13C NMR analysis. The CO2 capture efficiency of both fresh amines is about 88%, and that of the regenerated EMEA solutions decreases to about 79% once the equilibrium between amine regeneration (at 110 °C) and CO2-loaded amine has been reached. Instead, the efficiency of regenerated DGA progressively decreases to 69% at the end of the fifth cycle. 13C NMR analysis of the absorbed solutions of EMEA indicates that CO2 is captured as amine carbamate and bicarbonate (nearly 1:1 proportion), whereas DGA carbamate is the sole species of captured CO2. To improve the efficiency of regenerated DGA solutions, solid WO3 has been employed as desorption catalyst in five subsequent cycles of absorption and desorption. At equilibrium, the efficiency of CO2 capture increased to 85%, substantially greater than that of regenerated EMEA. The catalyst has been recovered unchanged at the end of each desorption step.

Synthesis and reactions of chroman-2-ols and their benzo analogs with N-nucleophiles

By the action of acetic acid on 2-morpholinochromanes, a series of chroman-2-ols were obtained in which the hydroxyl group is easily substituted by a primary or secondary amine or benzyl carbamate fragments. In the case of hydrazines and hydrazides of carboxylic acids, the corresponding hydrazones are isolated.

Resolution of ibuprofen with primary amine carbamates in supercritical carbon dioxide

Three new, successful resolving agents, namely (S)-2-phenylglycinol, (R)-1-phenylethanaminium (R)-(1-phenylethyl) carbamate and (S)-2-hydroxy-1-phenylethanaminium (S)-(2-hydroxy-1-phenylethyl) carbamate of ibuprofen are presented. The carbamate salts are stable white crystals, they can be easily stored and handled. All salt forming resolution were performed in supercritical carbon dioxide as the only solvent. The enantioseparations were efficient (approx. 50 % enantiomeric purities, > 90 % yields in the crystalline phase) and robust. Unlike previous experiences with primary amine resolving agents, the diastereomeric salt formations and resolutions were competed in short times, even within one hour suggesting that the carbamates are intermediates of the salt formation reaction.

Convergent synthesis of phosphonopeptides via phospha-Mannich reactions: Rationale on reactivity and mechanistic insights

Phospha-Mannich reactions of benzyl carbamate, aldehydes, and methyl dichlorophosphite followed by aminolysis with amino acid esters or alcoholysis with hydroxyl acid esters produce N-Cbz(benzyloxycarbonyl)-protected phosphonopeptides or phosphonodepsipeptides. However, similar reactions do not work when Cbz-amino amides are used instead of the carbamate. Phospha-Mannich reactions of N-Cbz-amino amides/2-(Cbz-amino)alkanesulfonamides, aldehydes, and dichloroarylphosphines and subsequent aminolysis with amino acid esters or alcoholysis with hydroxyl acid esters yield phosphinopeptides or phosphinodepsipeptides and hybrid sulfonophosphinopeptides or sulfonophosphinodepsipeptides. The different reactivities and mechanistic insights are rationalized that the α-amino alcohols generated from aldehydes and amides/sulfonamides show weaker nucleophilicity than those generated from aldehydes and benzyl carbamate. They can react with stronger electrophilic dichloroarylphosphines rather than weaker electrophilic methyl dichlorophosphite. The nucleophilicity of α-amino alcohols (amine reagents, carbamates, amides, and sulfonamides) and the electrophilicity of phosphorus reagents (dichloroarylphosphines and ethyl dichlorophosphite) control the reactivity of the phospha-Mannich reactions. Phosphorus trichloride is also efficient phosphorus reagent in the phospha-Mannich reactions because it is stronger electrophile as well.

Adverse Effects of Physostigmine.

Physostigmine is a tertiary amine carbamate acetylcholinesterase inhibitor. Its ability to cross the blood-brain barrier makes it an effective antidote to reverse anticholinergic delirium. Physostigmine is underutilized following the publication of patients with sudden cardiac arrest after physostigmine administration in patients with tricyclic antidepressant (TCA) overdoses. We completed a narrative literature review to identify reported adverse effects associated with physostigmine administration. One hundred sixty-one articles and a total of 2299 patients were included. Adverse effects occurred in 415 (18.1%) patients. Hypersalivation (206; 9.0%) and nausea and vomiting (96; 4.2%) were the most common adverse effects. Fifteen (0.61%) patients had seizures, all of which were self-limited or treated successfully without complication. Symptomatic bradycardia occurred in 8 (0.35%) patients including 3 patients with bradyasystolic arrests. Ventricular fibrillation occurred in one (0.04%) patient with underlying coronary artery disease. Of the 394 patients with TCA overdose, adverse effects were described in 14 (3.6%). Adverse effects occurred in 7.7% of patients treated with an overdose of an anticholinergic agent compared with 20.6% of patients with non-anticholinergic agents. Five (0.22%) fatalities were identified. In conclusion, significant adverse effects associated with the use of physostigmine were infrequently reported. Seizures were self-limited or resolved with benzodiazepines, and all patients recovered neurologically intact. Physostigmine should be avoided in patients with QRS prolongation on EKG, and caution should be used in patients with a history of coronary artery disease and overdoses with QRS prolonging medications. Based upon our review, physostigmine is a safe antidote to treat anticholinergic overdose.

Novel water-free biphasic absorbents for efficient CO2 capture

Screening tests of a number of amines and organic diluents indicated that 30% weight blends of 2-(methylamino)ethanol (MMEA) or 2-(ethylamino)ethanol (EMEA) with bis(2-ethoxyethyl) ether (DEGDEE) split into two liquid phases upon CO2 capture, an upper CO2 lean phase (mainly DEGDEE) and a lower CO2 enriched phase (mainly amine carbamate and protonated amine). These water-free biphasic absorbents have experimental CO2 loading capacity in the range 0.52–0.54. Besides batch experiments to measure the efficiency of CO2 capture and absorbent regeneration, the biphasic absorbents were tested in continuous cycles of CO2 (15% v/v in air) absorption–desorption carried out in packed columns. CO2 capture efficiency up to 97.6% was achieved with EMEA-DEGDEE and desorption temperature of the sole EMEA carbamate at 110°C. 13C NMR analysis was used to identify and quantify the species occurring in the different liquid phases. The features of the absorbent were compared to those of 30% weight aqueous MEA. The better performances of our absorbent were greater absorption efficiency, reduced flow rate in the desorber and avoidance of any parasitic diluent to be heated in the desorption step.

A Comparative Study of the CO2 Absorption in Some Solvent-Free Alkanolamines and in Aqueous Monoethanolamine (MEA).

The neat secondary amines 2-(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(isopropylamino)ethanol, 2-(benzylamino)ethanol and 2-(butylamino)ethanol react with CO2 at 50-60 °C and room pressure yielding liquid carbonated species without their dilution with any additional solvent. These single-component absorbents have the theoretical CO2 capture capacity of 0.50 (mol CO2/mol amine) due to the formation of the corresponding amine carbamates and protonated amines that were identified by the (13)C NMR analysis. These single-component absorbents were used for CO2 capture (15% and 40% v/v in air) in two series of different procedures: (1) batch experiments aimed at investigating the efficiency and the rate of CO2 capture; (2) continuous cycles of absorption-desorption carried out in packed columns with absorption temperatures brought at 50-60 °C and desorption temperatures at 100-120 °C at room pressure. A number of different amines and experimental setups gave CO2 capture efficiency greater than 90%. For comparison purposes, 30 wt % aqueous MEA was used for CO2 capture under the same operational conditions described for the solvent-free amines. The potential advantages of solvent-free alkanolamines over aqueous MEA in the CO2 capture process were discussed.

Carbon dioxide uptake as ammonia and amine carbamates and their efficient conversion into urea and 1,3-disubstituted ureas

Solid mixtures of ammonium carbamate and bicarbonate originating from the CO2 capture by NH3 in water–ethanol solution were converted into urea by heating to 428K for 60–90min. The yield of urea was up to 53% on molar basis. An analogous technique was employed to capture CO2 with 1-aminobutane, 1-amino-2-methylpropane, 2-amino-2-methylpropane, 1-aminooctane, aminocyclohexane and 1,4-diazacyclohexane, in organic solvents as amine carbamates which were separated in the solid state and thermally converted at 423K for 15–16h into 1,3-disubstituted ureas with 30–40% yield on molar scale. The formation of 1,3-disubstituted ureas was 100% selective. The rate of the conversion reaction was significantly improved in the presence of copper catalysts. The identification and quantification of the products in the reaction mixtures were obtained by 13C NMR analysis.

NMR-Based Carbamate Decomposition Constants of Linear Primary Alkanolamines for CO2 Capture

The amine carbamate related equilibrium (RNHCOO– + H2O ⇆ RNH2 + HCO3–) has been investigated with 13C NMR (Nuclear Magnetic Resonance) spectroscopy for a series of linear primary alkanolamines, and the apparent carbamate decomposition equilibrium constants have been estimated. A quantitative NMR method for the calculation of the concentration of the species formed in solution has been provided, including the assessment of each of the fast exchanging proton species (whose nuclei resonate at the same chemical shifts in the NMR spectra). For this purpose, NMR-based calibration curves were utilized and an alternative method was applied for validation. The overall results showed that the amount of carbamate found at the equilibrium decreased as the length of the carbon chain increased, while the corresponding apparent carbamate decomposition equilibrium constants featured the same order of magnitude (10–2).

(13)C and (15)N NMR characterization of amine reactivity and solvent effects in CO2 capture.

Factors influencing the reactivity of selected amine absorbents for carbon dioxide (CO2) capture, in terms of the tendency to form amine carbamate, have been studied. Four linear primary alkanolamines at varying chain lengths (MEA, 3A1P, 4A1B , and 5A1P ), two primary amines with different substituents in the β-position to the nitrogen (1A2P and ISOB), a secondary alkanolamine (DEA), and a sterically hindered primary amine (AMP) were investigated. The relationship between the (15)N NMR data of aqueous amines and their ability to form carbamate, as determined at equilibrium by quantitative (13)C NMR experiments, was analyzed, taking into account structural-chemical properties. For all the amines, the (15)N chemical shifts fairly reflected the observed reactivity for carbamate formation. In addition to being a useful tool for the investigation of amine reactivity, (15)N NMR data clearly provided evidence of the importance of solvent effects for the understanding of chemical dynamics in CO2 capture by aqueous amine absorbents.

Reactions of Amine and Peroxynitrite: Evidence for Hydroxylation as Predominant Reaction and New Insight into the Modulation of CO2

Peroxynitrite is related to numerous diseases including cardiovascular diseases, inflammation, and cancer. In order to expand the understanding for the toxicology of peroxynitrite in biological system, the reactions of amine (morpholine as a probe) with peroxynitrite and the modulation of CO2 were investigated by using DFT methods. The results strongly indicate that the hydroxylation of amine by peroxynitrous acid ONOOH, which was previously overlooked by most studies, is predominant relative to the widely reported nitration and nitrosation in the absence of CO2. The product N-hydroxylamine is proposed to be mainly generated via nonradical pathway (two-electron oxidation). The modulation of CO2 exhibits two main functions: (1) inhibition of hydroxylation due to the promoted consumption of peroxynitrite via fast reaction of CO2 with ONOO¯ to form ONOOCO2¯; (2) dual effect (catalysis and inhibition) of CO2 toward nitration and nitrosation. As a new insight, amine does react with CO2 and produce inert amine carbamate R2NCOO¯. This reaction has the potential to compete with the reaction of CO2 and ONOO¯, which leads to inhibition of nitration and nitrosation. The concentration of CO2 could be a critical factor determining the final effect, catalysis or inhibition. As a new finding, HCO3¯ is probably an effective catalyst for the reaction of amine and CO2. Moreover, further studies on how the different types of the amine might affect the outcome of the reactions would be an interesting topic.

Investigations of primary and secondary amine carbamate stability by 1H NMR spectroscopy for post combustion capture of carbon dioxide

Carbamate formation is one of the major chemical reactions that can occur in solution in the capture of CO2 by amine-based solvents, and carbamate formation makes a significant enthalpy contribution to the absorption-desorption of CO2 that occurs in the absorber/stripper columns of the PCC process. Consequently, the formation of carbamates of selected series of primary and secondary amines over the temperature range (288 to 318)K has been investigated by equilibrium 1H NMR studies, and the stability constants (K9) for the equilibrium:RNH2+HCO3-⇄K9RNHCOO-+H2Oare reported. van’t Hoff analyses have resulted in standard molar enthalpies, ΔHmo, and entropies, ΔSmo, of carbamate formation. A ΔHmo-ΔSmo plot generates a linear correlation for carbamate formation (providing a mean standard molar free energy, ΔGmo, for carbamate formation of about −7kJ·mol−1), and this relationship helps provide a guide to the selection of an amine(s) solvent for CO2 capture, in terms of enthalpy considerations. A linear ΔHmo-ΔSmo plot also occurs for carbamate protonation.The formation of the carbamates has been correlated with systematic changes in composition and structure, and steric effects have been identified by comparing molecular geometries obtained using density functional B3LYP/6-311++G(d,p) calculations. Trends in steric effects have been identified in the series of compounds monoethanolamine (MEA), 1-amino-2-propanol, 2-amino-1-propanol (AP) and 2-amino-2-methyl-1-propanol (AMP). In the case of 2-piperidinemethanol, 2-piperidineethanol and 3-piperidinemethanol, strong intramolecular hydrogen bonding is shown to be the likely cause for lack of carbamate formation, and in the ring systems of pyrrolidine, morpholine, piperidine and thiomorpholine trends in carbamate formation (as given by K9) have been correlated with the internal ring angle at the amine nitrogen, as well as the planarity of the environment around the nitrogen atom.

Optimum design of multi-stage isotope separation process by exergy analysis

A separation process of carbon isotopes, 12C (98.9%), 13C (1.1%) and 14C (trace), by the chemical exchange reactions between CO 2 and amine carbamate was designed by the exergy analysis technique and the applicability of the exergy analysis to the design of isotope-separation process is discussed. The exergy loss ( EXL) for the single-column process was increased exponentially toward the product end, because of the mixing of isotopes between gas and liquid flows. By the application of ideal cascade without the mixing of 14C and 12C, the EXL value was reduced to 10% of that for the single-column process. The ideal cascade gives the minimum volume of separation column reasonably, however, is impracticable as an industrial process, because of the complexity of process configuration and operation. From the viewpoint of practical use, a squared-off cascade with three columns, whose diameters were reduced toward the product end, was designed under the condition that the difference of EXL between the squared-off cascade and the ideal one was minimized. The EXL value of this process was evaluated as about 12% of that of single-column process and the separation performance was similar to that for the ideal cascade. These results suggest that the process design method based on exergy analysis is very useful as a tool to design an optimum squared-off cascade.

Smart cleavage reactions: the synthesis of an array of ureas from polymer-bound carbamates.

The solid-phase synthesis of a library of di-, tri-, and tetrasubstituted ureas is described. In this approach, an array of polymer-bound carbamates was synthesized. These polymer-bound primary and secondary amine carbamates were then treated under "smart" diversity-building cleavage conditions using a series of aluminum amide complexes to form the corresponding urea cleavage products. The crude cleavage products from this study were isolated in excellent yield and purity. To show the applicability of this strategy, a series of biaryl ureas were synthesized using sequential solid-phase Suzuki coupling and urea formation reactions.

Enrichment of 13C by chemical exchange between CO2and amine carbamate in nonaqueous solvents

Enrichment of 13C by chemical exchange between CO2 and amine carbamate in nonaqueous solvents has been mathematically modelled in two ways. The height equivalent to a theoretical plate and steady-state separation, based on the two models, have been obtained. If only the isotopic exchange between CO2 gas and amine carbamate is considered, the model can estimate the process performance for pressures close to the atmospheric one and room temperature. For process analysis at pressures higher than the atmospheric one and lower temperatures, a two-step model has been used. Using the two models the effects of pressure have been studied.

SIMPLE ROUTE TO CYCLOPENTANOL DERIVATIVES

We described here an efficient and short new method to synthesize cyclopentanol derivatives. Ring opening of spiroepoxide 3 was done easily by an amine or ethyl carbamate leading to new molecules bifunctionalized. The characteristic 1H and 13C NMR spectroscopic features of the synthesized compounds are reported.

Carbon dioxide but not bicarbonate inhibits N-nitrosation of secondary amines. Evidence for amine carbamates as protecting entities.

Hydrogen carbonate (bicarbonate, HCO(3)(-)) has been proposed to accelerate the decomposition of N(2)O(3) because N-nitrosation of morpholine via a nitric oxide/oxygen mixture ((*)NO/O(2)) was inhibited by the addition of HCO(3)(-) at pH 8.9 [Caulfield, J. L., Singh, S. P., Wishnok, J. S., Deen, W. M., and Tannenbaum, S. R. (1996) J. Biol. Chem. 271, 25859-25863]. In the study presented here, it is shown that carbon dioxide (CO(2)) is responsible for this kind of protective effect because of formation of amine carbamates, whereas an inhibitory function of HCO(3)(-) is excluded. N-Nitrosation of morpholine (1-10 mM) at pH 7.4-7.5 by the (*)NO-donor compounds PAPA NONOate and MAMA NONOate (0.5 mM each) was not affected by the presence of large amounts of HCO(3)(-) (up to 100 mM) in aerated aqueous solution. Similar results were obtained by replacing the (*)NO-donor compounds with authentic (*)NO (900 microM). In agreement with data from the study cited above, (*)NO/O(2)-mediated formation of N-nitrosomorpholine (NO-Mor) was indeed inhibited by about 45% in the presence of 50 mM HCO(3)(-) at pH 8.9. However, 500 MHz (13)C NMR analysis with (13)C-enriched bicarbonate revealed that significant amounts of morpholine carbamate are formed from reaction of equilibrated CO(2) with morpholine (1-100 mM) at pH 8.9, but only to a minor extent at pH 7. 5. The protective effect of morpholine carbamate formation is explained by a significantly reduced charge density at nitrogen. This view is supported by the results of density functional theory/natural population analysis, i.e., quantumchemical calculations for morpholine and morpholine carbamate. In agreement with its lower pK(a), another secondary amine, piperazine, had already produced significant amounts of piperazine carbamate at pH 7. 4 as shown by (13)C NMR spectrometry. Consequently, and in contrast to morpholine, N-nitrosation of piperazine (2 mM) by both (*)NO/O(2) (PAPA NONOate, 0.5 mM) and the (*)NO/O(2)(-)(*)-releasing compound SIN-1 (1 mM) was inhibited by about 66% in the presence of 200 mM HCO(3)(-).

5726251 Powder coatings of amine-reactive resins and amine carbamate salts

5726251 Powder coatings of amine-reactive resins and amine carbamate salts