Purification Of Salts Research Articles

Electrochemical deposition combined with high-temperature molecular sieve adsorption strategy: Efficient removal of key fission element yttrium for purification of radioactive molten salts

In order to realize energy cost savings in waste salt recycling and electrolysis processes during the nuclear fuel cycle, this paper presents a novel approach for the purification of waste molten salt by employing molecular sieves to absorb excess fission products selectively. The method is founded on the principles of electrolytic refining to achieve sustainable development of reprocessing. In this study, a systematic investigation of the electrochemical reduction/oxidation processes of Y(III)/In(III) was performed on electrode, as well as the electrode reaction of Y(III) on an In electrode at 773 K. Constant-current electrolysis produced an extraction rate of 93.11 % for Y(III) on the In electrode. In order to improve the current efficiency, greatly save the processing cost, and realize the sustainable development of dry post-processing. Subsequently, the waste molten salt environment following electrolysis was simulated, and the fission product was effectively adsorbed utilizing 5A molecular sieves, resulting in a yttrium removal rate of up to 99.94 %. This process not only significantly reduces the cost of electrolysis but also enhances the removal efficiency of target nuclides. The study examined the molten salt adsorption mechanism of molecular sieve, determining the primary adsorption mechanism to be chemical one (ion exchange), through the application of pseudo-first-order, pseudo-second-order, and Weber-Morris kinetic models for re-evaluation.

Separation of uranium from lanthanides (La, Ce, Nd) and purification of waste salt via aluminum electrodes with different structures in LiCl-KCl eutectic

Aluminum is an ideal cathode material for the pyrochemical reprocessing of spent nuclear fuels. However, there is a lack of large-scale experiments to further assess its performance. Here we designed several Al electrodes with sheet, rod, and porous morphologies, and employed them in separating actinides (An) from lanthanides (Ln) and purifying the waste salts in about 500 g of LiCl-KCl eutectic melt at 773 K. By applying a constant potential of −1.2 V vs. Ag/AgCl, U can be separated from Ln (La, Ce, and Nd) by forming Al-U alloys consisting of Al3U and Al4U with high separation factors and current efficiency. Among all Al electrodes used in our experiments, the porous-shaped ones show the fastest electrochemical reaction rate, and hence only 56 h were required to achieve the separation. Subsequently, the purification of the waste salts from U-Ln separation was conducted via constant potential electrolysis at −1.5 V vs. Ag/AgCl on porous-shaped Al electrodes. About 99.9 % of Ln was extracted via forming Al-Ln alloys, leaving a purified electrolyte that can be reused. In all, about 17 g of U metals and 1 kg of waste salts were successfully reprocessed in our large-scale experiments, which envisions the feasibility of applying Al electrodes in engineering-scale pyrochemical reprocessing.

Real-time control of distillation process to improve the recovery efficiency of ThF4-LiCl-KCl molten salt.

The purification and recovery of chloride electrolyte molten salts are vital to reuse this valuable species and reduce the waste. Vacuum distillation method was used to investigate the recovery efficiency of LiCl-KCl mixed molten salt containing 20 wt% ThF4. Rapid mass loss in the initial stage and the subsequent lower evaporation rate were significantly observed under 1173 K and 20 Pa due to the coordination species such as Li3ThF7 and LiTh2F9. To achieve the recovery efficiency of chloride salts, a real-time control distillation was proposed. The distillation was terminated when about 80% mixture salt was evaporated according to the transient weight loss curve. The evaporation ratio of LiCl-KCl reached 91% and the decontamination factors for Th and rare earth elements Nd and Sm were more than 103 and 102, respectively. The results provided a simple and effective scheme to separate ThF4 and recover molten salts from waste electrolyte salts.

Efficiency of Electrochemical Methods of Purification and Control over the Oxide Concentration in Halide Melts: PbCl2

The purification of molten salts from admixtures as well as the effective control of admixture concentration has attracted researchers’ interests. In the present paper, the possibility of the electrochemical purification of PbCl2 from PbO and the effective control over the oxide ions concentration in molten PbCl2 is studied at the temperature of 520 °C. The PbCl2 melt with the initial addition of 0.5 wt% of PbO was used as a molten salt sample. The method of potentiostatic electrolysis was used to remove the oxide additions from the melt; the linear and square-wave voltammetry dependencies were recorded, and the melt samples were taken for analysis. Based both on the results of the electrochemical measurements and the analysis of oxygen concentration in the electrolyte, we built linear empirical dependencies of the anode peak current of the oxidation of oxygen-containing electroactive anions on the PbO concentration in the studied melt. We demonstrated that the obtained dependencies may be used for direct electrochemical nondestructive in-situ control over the concentration of PbO dissolved in the PbCl2 melt containing up to 0.5 wt% of PbO. The deep electrochemical purification of the chloride PbCl2 melt from molten oxide (up to 0.044 wt% PbO or to 0.007 wt% of oxygen) was achieved by the potentiostatic electrolysis.

Investigation on Purification of Saturated LiNO3 Solution Using Titanium Phosphate Ion Exchanger: Kinetics Study

Lithium compounds are of high interest to many industries. The presence of undesirable impurities in Li precursors leads to uncontrolled change in the functional properties of final compounds. Therefore, the development of reliable methods for lithium salt purification is considered a key factor for their application in various industries. This work focuses on the application of a titanium phosphate ion exchanger (Li-TiOP) toward Cu2+, Co2+, Mn2+, Ni2+, and Cr3+ ions in the purification of a saturated LiNO3 solution. The sorption kinetics of the selected ions, considering external and internal mass transfer, as well as chemical interaction, were deeply studied. The kinetic study showed that the values of intraparticle diffusion rate and effective diffusion coefficients for the studied ions decreased in the following order: Cr(III) ˃ Cu(II) Mn(II) ˃ Co(II) ˃ Ni(II). For all the selected ions, chemical interaction was described with a pseudo-second-order reaction model. The sorption kinetics were controlled by the size of the solvated metal ion, its effective charge, the electronic structure of the adsorbed ion, and the interaction with the functional groups of the sorbent. Due to fast kinetics, the high degree of removal of trace quantities of the impurities this material gives it consideration as a promising sorbent for the deep purification of lithium salts.

Polyelectrolyte multilayers coating of aliphatic polyamide anion-exchange membranes to increase monovalent/divalent anions selectivity in electrodialysis

Layer-by-layer (LBL) modification of aliphatic polyamide anion-exchange membranes (AEMs) with poly(4-styrenesulfonate) (PSS) and protonated poly(allylamine) (PAH) coatings increases monovalent/divalent anion transport selectivities. Remarkably, in electrodialysis (ED) Cl−/SO42− selectivities increase from 1.3 to ∼180. In addition, current efficiencies reach ∼90 %. Selectivity, however, decreased to ∼50 when the Cl−/SO42− source-phase ion concentrations increased from 10 to 100 mM and from ∼180 to ∼10 when the current density went up from 0.63 to 2.23 mA·cm−2. The current efficiency also went down to ∼50 % at 2.23 mA cm−2 which indicates the introduction of some parasitic phenomenon at higher current densities. Moreover, for a coated membrane, the polyelectrolyte multilayer (PEM) coating facing the source phase is comparatively more selective in ED whereas the PEM facing the receiving phase is relatively more selective in diffusion dialysis (DD). Also, the (PSS/PAH)11–films (11 bilayers of PSS and PAH polyelectrolytes) which are terminated in polycations show much lower Cl−/SO42− selectivity and current efficiency as compared to the (PSS/PAH)10PSS-films (10 bilayers of PSS and PAH polyelectrolytes capped with a layer of PSS polyelectrolyte) which are terminated in polyanions. These relatively inexpensive but highly selective and current efficient AEMs can be used in ED for the purification of salts containing divalent and/or multivalent anions.

An Alternative Method for the Synthesis of N-Pentafluorophenyl Triazolium Salts.

A route for the synthesis of 1,2,4-triazolium salts via oxidation of a thione precursor is demonstrated. N-Pentafluorophenyl-substituted salts are produced in 20-63% overall yields. Isolation and purification of the azolium salts are simplified compared to the traditional synthetic route. Late-stage selection of the counterion allows the synthesis of a variety of salts from a parent thione. The salts have been compared in Stetter and cross-benzoin reactions with an appreciable counterion effect in both reactions.

Chloride Salt Purification by Reaction With Thionyl Chloride Vapors to Remove Oxygen, Oxygenated Compounds, and Hydroxides

Molten chloride salts (including MgCl2, KCl, NaCl, and ZnCl2) are being considered for heat transfer media for renewable (solar) and nuclear power generators, as fuel carrier for nuclear reactors, and as thermal energy storage media. Impurities such as oxygen, hydroxides, moisture, and sulfur are known to negatively influence the corrosion of materials in contact with the salt (e.g., structural metals). Commercially available chloride salts come with a range of impurities. Before using the chloride salts at high temperature, it is desirable to remove the impurities to increase the performance of the salt and reduce corrosion. In this study, we tested the use of thionyl chloride vaporized into a stream of argon to react with oxygenated impurities in a mixture of MgCl2-KCl-NaCl, removing them as HCl and SO2. The reagent was bubbled through the salt when both above and below the melting point. The reaction was followed using thermocouple data from the salt and by Fourier transform infrared (FTIR) spectroscopy on the exhaust of the reactor. The reaction kinetics were followed by comparing the peaks from SO2 product to SOCl2 reagent in the FTIR spectra. The purity of the salt was assessed at the end of the purification process by x-ray diffraction and inductively coupled plasma analysis. Although the process was effective in removing the oxygen content of the mixture, ternary compounds were formed in the process, including KNiCl3 and KMgCl3. The nickel in KNiCl3 came from the reaction between the salt and the nickel vessel. Thus, these experiments suggest that improvements to the process must be made before using SOCl2 vapors for the purification of chloride salts.

PHYSICAL AND CHEMICAL FOUNDATIONS OF THE EXTRACTION REFINING OF NATURAL URANIUM

The paper presents the results of studies of the physicochemical processes of the extraction and nitric acid purification of uranium salts obtained by the method of precipitation of ammonium uranyl carbonate (AUC) from ore solutions of leaching of uranium and polymetallic ores with their subsequent dissolution in nitric acid. It is shown that the process of extraction on a mixture of tributyl phosphate (TBP) in kerosene makes it possible to obtain high-purity uranium oxide. For the selective extraction of impurities, the process of uranium extraction from the nitric acid medium was carried out with a mixture of TBP and di(2-ethylhexyl) phosphoric acid (DEHPA) in kerosene. The first uranium concentration 40…50 g/L simulated the process of uranium desorption, the second ≤ 100 g/L simulated the process of dissolution of uranium oxide. The study of the uranium extraction made it possible to determine the required number of extraction stages to achieve the minimum uranium content in the raffinate and the maximum extractant capacity, which ensured the specified coefficients of uranium purification from metal impurities (V, Mo, etc.). After extraction, the nitric acid raffinate served as a raw material for the production of a mineral fertilizer – sodium nitrate.

Low-pressure highly permeable polyester loose nanofiltration membranes tailored by natural carbohydrates for effective dye/salt fractionation

With the continuous pressure of water contamination caused by textile industry, loose nanofiltration (LNF) membranes prepared by green materials with an extraordinary water permeability are highly desirable for the recovery and purification of dyes and salts. In this work, low-pressure LNF membranes with ultrahigh permeability were fabricated via one-step interfacial polymerization (IP), in which inexpensive natural carbohydrate-derived sugars with large size and low reactivity were utilized as aqueous monomers to design selective layer. A systematic characterization by chemical analysis and optical microscopy demonstrated that the formed polyester film features not only loosen the structure, but also results in a hydrophilic and negatively charged surface. The optimized sucrose-based membrane (Su0.6/TMC0.1) with an excellent water permeability of 52.4 LMH bar−1 was found to have a high rejection of dyes and a high transmission of salts. In addition, the sugar-based membrane manifested an excellent anti-fouling performance and long-term stability. Furthermore, the non-optimized Gl0.6/TMC0.1 and Ra0.6/TMC0.1 membranes also shown a high water permeability, while maintaining a competitive dye/salt separation performance, which confirmed the universal applicability of the membrane design principle. Therefore, the proposed new strategy for preparing next-generation LNF membranes can contribute towards the textile wastewater treatment.

Detection of Ru potential metallodrug in human urine by MALDI-TOF mass spectrometry: Validation and options to enhance the sensitivity

We studied the possibility of detection of [Ru(η5-C5H5)(PPh3)2Cl] (abbreviated by RuCp) complex as a model system for Ru-based metallodrugs in human urine by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) without previous purification or removal of inorganic salts. Inorganic salts might prevent the detection of RuCp by MALDI-TOF MS, most likely through the increased number and intensity of background/organic matrix signals. This problem might be overcome by the acquisition of matrix-free spectra and the addition of nanoparticles, such as carbon dots, to the urine solution. Our results suggest that RuCp is easily detectable by MALDI-TOF MS in all acquisition conditions, with the CHCA matrix being the best for acquisition in phosphate-containing solutions, whereas in urine, DHB and matrix-free approach demonstrated the highest sensitivity, precision, and reproducibility. The sensitivity of matrix-free MALDI detection of RuCp could be increased by the addition of carbon dots to the urine. Based on theoretical calculations for all matrix/analyte combinations, the model for the interaction of RuCp with carbon dots was established, and higher sensitivity explained.

Syncytiotrophoblast basal membrane-derived exosomes increase NO generation in human umbilical vein endothelial cells

Rhenium and molybdenum are valuable metals present in the earth's crust in very low concentration and are increasingly used in industry thanks to their multiple properties, but due to the harmful aspects of the production process, there is a need to develop systems of concentration or purification of salts of these elements. For this work a PEG/Na2MoO4 aqueous two phase system (ATPS) was used for the partition of ReO4- anion. By using a central composite design, the effects of PEG concentration, sodium molybdate concentration, temperature, pH and their possible interaction on the partition coefficient were studied, also to estimate the optimal configuration of the factors that influence the process. At the same time, experimental density, sound velocity and isentropic compressibility were also obtained for top and bottom phases. The results showed that the optimal conditions for the partition of ReO4− anion using the ATPS formed by PEG and Na2MoO4 were 14.7 wt% PEG 4000, 16.3 wt% Na2MoO4, 35 °C and pH 6. For these conditions, the partition coefficient (K) obtained was up to 17.8 ± 0.78. The order of factors with high significance on the partition coefficient was: Na2MoO4 concentration > PEG concentration > temperature > pH > interaction between Na2MoO4 and PEG concentrations; the effect of these parameters mainly is related with the speciation, salting-out effect and hydrophobicity. The influence of these factors on the density, and sound velocity of the top phase was minimal, unlike its influence on the properties of the bottom phase, not isentropic compressibility and effect of PEG and Na2MoO4 concentrations on sound velocity. The evaluation of the partitioning behavior was made by experimental design, applying statistical regression analysis and analysis of variance (ANOVA). The statistical models for partition coefficient and for phase densities (and the other properties) as function of parameters with significant effects were obtained, and also a good correlation between experimental and correlated data was observed (R-Squared = 0.9379, ReO4− partition coefficient; 0.9882, bottom phase; and 0.9836 upper phase). This work is oriented to the possible application in stripping of a top phase provided for a co-extraction of rhenium and molybdenum by ATPS in acidic media or in solutions with high contend of Mo such as those provided by pressure oxidative leaching of molybdenite in basic media.

Application of central composite design to the partition of perrhenate anion in aqueous two phase system Na2MoO4 + PEG 4000 + H2O

Rhenium and molybdenum are valuable metals present in the earth's crust in very low concentration and are increasingly used in industry thanks to their multiple properties, but due to the harmful aspects of the production process, there is a need to develop systems of concentration or purification of salts of these elements. For this work a PEG/Na2MoO4 aqueous two phase system (ATPS) was used for the partition of ReO4- anion. By using a central composite design, the effects of PEG concentration, sodium molybdate concentration, temperature, pH and their possible interaction on the partition coefficient were studied, also to estimate the optimal configuration of the factors that influence the process. At the same time, experimental density, sound velocity and isentropic compressibility were also obtained for top and bottom phases. The results showed that the optimal conditions for the partition of ReO4− anion using the ATPS formed by PEG and Na2MoO4 were 14.7 wt% PEG 4000, 16.3 wt% Na2MoO4, 35 °C and pH 6. For these conditions, the partition coefficient (K) obtained was up to 17.8 ± 0.78. The order of factors with high significance on the partition coefficient was: Na2MoO4 concentration > PEG concentration > temperature > pH > interaction between Na2MoO4 and PEG concentrations; the effect of these parameters mainly is related with the speciation, salting-out effect and hydrophobicity. The influence of these factors on the density, and sound velocity of the top phase was minimal, unlike its influence on the properties of the bottom phase, not isentropic compressibility and effect of PEG and Na2MoO4 concentrations on sound velocity. The evaluation of the partitioning behavior was made by experimental design, applying statistical regression analysis and analysis of variance (ANOVA). The statistical models for partition coefficient and for phase densities (and the other properties) as function of parameters with significant effects were obtained, and also a good correlation between experimental and correlated data was observed (R-Squared = 0.9379, ReO4− partition coefficient; 0.9882, bottom phase; and 0.9836 upper phase). This work is oriented to the possible application in stripping of a top phase provided for a co-extraction of rhenium and molybdenum by ATPS in acidic media or in solutions with high contend of Mo such as those provided by pressure oxidative leaching of molybdenite in basic media.

A new approach for salts removal from crude glycerin coming from industrial biodiesel production unit

The aim of the present work is to propose purification and cleaning of the residual salt from the crude glycerin purification step from distillation, using relatively simple physicochemical processes and easy industrial implementation. For this purpose, Total Organic Carbon (TOC), chloride content, metal analysis (Na, K, Ca and Mg), glycerol content, moisture content, total solids and ash content were employed to characterize the crude sample. The crude sample was extracted using different solvents (methanol, ethanol, chloroform, and dichloromethane), where methanol proved to be the most efficient solvent for extracting the organic phase of the sample under study. It was evaluated the ratio of residual salt:solvent (1:3, 1:5 and 1:10) which afforded the highest extraction efficiency as well as the required reaction time for the same (1, 5, 10 and 15 min). After obtaining the treated sample, it was subjected to the same characterization analyzes of the crude sample, for comparison. Results indicate that both the yield and quality of the recovered salt are governed not by the time of contact, but by the residual salt:solvent ratio. A significant reduction in total organic carbon (TOC) was observed between crude and treated samples, which was accompanied by an expressive increase in salt content, mainly for chloride and sodium ions. From a social and economic point of view, the purification of sodium chloride salts allows the use of a residue with potential application as a mineral salt.

Enabling chloride salts for thermal energy storage: implications of salt purity.

Molten salts for use as heat transfer fluids in concentrated solar or nuclear power plants have experienced a resurgence over the past decade with a special focus on chloride-based salt mixtures, particularly for use in concentrating solar power and fast-spectrum nuclear reactors. Salt purification, specifically oxide removal, is required even for high purity commercial salts and can be achieved using many different methods. Carbochlorination, however, proves most effective according to thermodynamics and produces a gaseous byproduct easily removed from the salt. A variety of carbochlorinating reagents and reagent combinations were evaluated for thermodynamic favorability in the removal of common impurities in MgCl2-based feedstock or coverage gases used in industrial systems. Carbon tetrachloride exhibited superior purification thermodynamics above the melting point of common MgCl2-based salt compositions. Salt with composition of 68 : 32 mol% KCl : MgCl2 was purified on the kilogram scale by sparging with carbon tetrachloride, reducing dissolved oxide to trace levels (42 μmol MgO/kg salt). Interestingly, the lower purity salts exhibited magnesium and oxygen presence along grain boundaries in the corrosion layers while the purified salts did not, highlighting the need for decreased oxide content. The lessened corrosivity of the highly purified salt suggests a proper salt treatment may reduce dependence on specialized materials for use with molten salts.

Gas Antisolvent Fractionation: a New Method to Obtain Enantiopure Compounds, a Case Study on Mandelic Acid

Micronization processes involving supercritical carbon dioxide are rapid methods to produce fine particles. They also might offer the possibility of using less organic solvent than conventional crystallization methods leading to an environmentally friendlier processing. The separation capabilities of such processes are now demonstrated on the diastereomeric resolution of mandelic acid using (R)-1-phenylethanamine as a resolving agent, utilizing the batch type gas antisolvent fractionation as the separation method. A detailed study was conducted on the effects of the operational parameters pressure (12-20 MPa), temperature (35-55 °C) and co-solvent concentration (33-99 mg/ml). At 12 MPa, 35 °C and 99 mg/ml methanol concentration, a selectivity of 0.52 and a diastereomeric excess of 62% was reached. The same operational parameters were applied during the investigation of the recrystallization-based further purification of the diastereomeric salts, applying the resolving agent in molar equivalent quantity to a non-racemic mixture of mandelic acid. It has been found that the more stable (R)-1-phenylethylammonium-(R)-mandelate salt can be purified to de>98% through four additional recrystallization steps following the initial, half-molar equivalent resolution step.

Water Purification of Dyes and Hardness Salts by Ceramic Membranes Modified with Silica and Pyrocarbon

Modification of ceramic membranes was conducted with silica, obtained from liquid glass, and pyrocarbon from carbonized polyisocyanate and sucrose at 800°C. Water from Ca2+ and direct scarlet dye was purified by a pressure-driven method at 0.7 and 1.1–1.2 MPa. The retention coefficient of Ca2+ and specific productivity of the modified membranes depending on filtration time decreased respectively from 63 to 8% and from 150 to 4.7 dm3/(m2.h). For direct scarlet dye, the retention factor constitutes 99.0 and 99.9% at the specific productivity respectively 27 and 1.8 dm3(m2.h).

Fast further purification of diastereomeric salts of a nonracemic acid by gas antisolvent fractionation.

A novel, green possibility of the further purification of the diastereomeric salt of 4-chloromandelic acid and 1-phenylethane-1-amine was developed. Gas antisolvent method using supercritical carbon dioxide was applied for the first time to precipitate the diastereomeric salts with increased purity followed by the supercritical fluid extraction of the dissolved diastereomers. The RR-salt can be purified to >99%, while fractionation-based purification of the SR-salt is limited to ~80%. The limiting initial diastereomeric excess correlates strongly with the atmospheric melting eutectic composition of the same salts, which suggests that despite the fast precipitation, the diastereomeric excess of the solid product is not kinetically determined. The efficiency of the diastereomeric enrichment is in the same range as that of the atmospheric reference experiments; however, technological advantages provided by the antisolvent precipitation method such as fast processing and dry product obtained suggest that this novel procedure is a promising alternative to the atmospheric methods.

Purification of rare earth bis(trifluoromethyl-sulfonyl)amide salts by hydrometallurgy and electrodeposition of neodymium metal using potassium bis(trifluoromethyl-sulfonyl)amide melts

This paper reports a novel bench-scale hydrometallurgical procedure and electrodeposition using potassium bis(trifluoromethyl-sulfonyl)amide (KTFSA) melts for the recovery of rare earth (RE) elements from Nd-Fe-B magnet waste. The investigations were performed at bench scale to assess the potential of a process based on leaching, deironization, and purification of RE amide salts. In the leaching process using 3.4 kg of oxidized Nd-Fe-B and 14.2 L of an aqueous solution of 1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide (HTFSA), 83.0% Nd and 0.98% Fe were leached in 13 h, indicating that selective leaching of RE elements was performed at bench scale. Then, KOH or oxidized Nd-Fe-B was used as a precipitation agent in the deironization process and 100.0% Fe was successfully separated from RE components. Moreover, 4.07 kg of purified amide salts (M(TFSA)3, M = Pr, Nd, Dy, B, Al, and trace elements) were recovered from a spray dryer. The electrochemical behavior of Nd(III) in KTFSA melts containing M(TFSA)3 (molar fraction of RE components: xRE = 0.1) was investigated in this study. Electrochemical analysis revealed that the reduction peak of Nd(III) at around +1.0 V vs. K/K+ was due to the following reaction: Nd(III) + 3e− → Nd(0). The diffusion coefficient of Nd(III) was estimated to be 3.14 × 10−10 m2 s−1 at 483 K by semi-differential analysis, which is similar to that of Nd(III) in KTFSA melts containing pure Nd(TFSA)3 salts (xNd = 0.1). The electrodeposition of Nd was performed under potentiostatic conditions of +0.8 V vs. K/K+ at 483 K. The electrodeposits had a fine surface morphology with small metal particles. The electrodeposits were confirmed to be Nd metal in the middle layer analyzed by scanning electron microscopy/energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Finally, we demonstrated the effectiveness of the novel recovery process for practical use by estimating whole material flow.

ChemInform Abstract: Rapid Conventional and Microwave‐Assisted Decarboxylation of L‐Histidine and Other Amino Acids via Organocatalysis with R‐Carvone under Superheated Conditions.

AbstractThis article reports a new methodology taking advantage of superheated chemistry via either microwave or conventional heating for the facile decarboxylation of alpha amino acids using the recoverable organocatalyst, R-carvone. The decarboxylation of amino acids is an important synthetic route to biologically active amines, and traditional methods of amino acid decarboxylation are time consuming (taking up to several days in the case of L-histidine), are narrow in scope, and make use of toxic catalysts. Decarboxylations of amino acids including L-histidine occur in just minutes while replacing toxic catalysts with green catalyst, spearmint oil. Yields are comparable to or exceed previous methods and purification of product ammonium chloride salts is aided by an isomerization reaction of residual catalyst to phenolic carvacrol. The method has been shown to be effective for the decarboxylations of a range of natural, synthetic, and protected amino acids.