化学交换精馏法分离同位素硼-10研究进展

综述了化学交换精馏法分离同位素硼-10的技术进展。在介绍化学交换精馏法分离同位素硼-10原理的基础上,分析了目前工业化过程分离同位素硼-10存在的问题,指出新的络合剂-硝基甲烷(CH3NO2)、丙酮(Acetone)、甲基异丁基酮(MIBK)、二异丁基酮(DIBK)等用于从三氟化硼分离硼-10具有更高的分离系数,形成的络合物具有更好的稳定性,其中CH3NO2是现有同位素硼-10分离工艺过程较为理想的替代络合剂。     

The boron trifluoride monoethyl amine complex cured epoxy resins

The curing exotherm pattern is affected by the equivalent ratio of curing agent, boron trifluoride monoethylamine complex (BF₃ · MEA), to epoxy resin. The diglycidyl ether of 9,9-bis(4-hydroxyphenyl) fluorene (DGEBF) cures more slowly than the diglycidyl ether of bisphenol A (Epon 828). The glass transition temperatures (T_g's) of BF₃ · MEA cured Epon 828 are increased with inceasing concentration of curing agent (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF₃ · MEA (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF₃ · MEA (0.0450 eq./epoxy eq.) cured Epon 828 and DGEBF are almost equivalent 43 and 44 kcal/mol, respectively. DGEBF when added to DGEBA improves the T_g and char yield with the BF₃ · MEA curing system. The T_g of both resin systems can be increased by longer post cure, whereas the char yield does not appear to change significantly. No ester group formation is found for the BF₃ · MEA-cured DGEBF, although this has been previously reported for the DGEBA system. The BF₃ · MEA cure at 120°C is better than at 140°C because of vaporization and degradation of the curing agent at the higher temperature. The rapid gelation of the epoxy resin may be another reason for the lower degree of cure at high temperature.     

Synthesis and properties of polyaryletherketones

Crystalline polyarletherketones of high molecular weight have been prepared previously by polycondensation of aroyl fluorides such as 4-phenoxybenzoyl fluoride in liquid HF, but not by polyether synthesis because these polymers are not soluble in the recommended (see Farnham et al., J. Polym. Sci., Al, 1967, 5, 2375) dipolar aprotic solvents such as dimethyl sulphoxide or sulpholane. We find that tough, crystalline polyaryletherketones and copolyaryletherketone-sulphones can be obtained by polycondensation of bis-4-halogenophenyl ketones (plus bis-4-halogenophenyl sulphones for copolymers) with the potassium salts of bis-4-hydroxyphenyl ketones at 280°–340°C using certain diaryl sulphones as solvents for the reactions. There is no evidence for structural anomalies in the polyetherketone made by polycondensation of bis-4-fluorophenyl ketone with the bis-phenoxide from bis-4-hydroxyphenyl ketone, but synthesis of this polymer by polycondensation of the potassium salt of 4-fluorophenyl 4-hydroxyphenyl ketone gave products containing some gel and soluble polymer in which the chains appear to be branched. Several different polyaryletherketones give almost identical X-ray diffraction patterns, and in the unit cells of these polymers (fibre repeat distance 10.0Å) ether and carbonyl linkages are interchangeable; T_g and T_m for these polymers are recorded.     

The polymerization mechanism and kinetics of DGEBA with BF3-MEA

The diglycidyl ether of bisphenol-A (DGEBA) and boron trifluoride monoethylamine (BF₃-MEA) were used in a model system to investigate the chemical and physical changes that occur during polymerization. Experiments using ¹⁹F and ¹H nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) showed that BF₃-MEA breaks down rapidly into HBF₄ and an amine salt at 85°C and above. The HBF₄ complexes with the epoxy groups, producing an activated monomer that reacts with epoxy in an etherification reaction. A mechanism is proposed whereby activated epoxy sites (complexes) continuously add epoxy throughout the reaction, but where unactivated epoxies (monomer molecules) are unable to react with each other. The reaction rate and mode (kinetic vs. diffusion control) therefore are strongly influenced by the BF₃-MEA concentration and the reaction temperature. © 1993 John Wiley & Sons, Inc.     

Cationic copolymerization of phenyl glycidyl ether with lactones. Characterization of the reaction mixture with chromatographic methods

This paper refers to the influence of the catalysts boron trifluoride p-methoxyaniline complex (BF₃ · MA) and boron trifluoride etherate complex (BF₃ · Et₂O) having different reactivity in cationic copolymerization of phenyl glycidyl ether (PGE) with γ-butyrolactone (γ-BL) and ϵ-caprolactone (ϵ-CL), respectively. Reactions were followed by FT-IR, HPLC and SEC. SEC with multiple detection and Two-Dimensional-Chromatography HPLC/SEC were used to characterize the products in view to their copolymer compositions. In the presence of BF₃ · MA a preferred formation of spiroorthoesters (SOE) was observed; the polymerization of SOE under these conditions can be neglected. In case of the more reactive BF₃ · Et₂O the epoxide homopolymerization strongly competes with SOE formation, resulting in a product mixture of epoxide homopolymers (and in the case of ϵ-CL also lactone homopolymers) and copolymers with low lactone content.     

Alkyl aryl ethers in lignite solubilization. 1. Study of the process

The chemistry of solubilization of a lignite has been investigated with anisole, 3-methyl anisole and 1,3-dimethoxybenzene catalysed by SbCl₃, ZnCl₂, AlCl₃ and BF₃ as boron trifluoride etherate, at atmospheric pressure and temperatures < 220 °C. 60% of lignite was solubilized in a toluene-ethanol azeotropic mixture. During the process, the solvent is incorporated as an alkylated substratum. The yield increased with activity of the aromatic ether ring and catalyst acidity.     

Dielectric and gas transport properties of the films of thermally stable poly(arylene ether ketone)s containing content‐tunable benzimidazole moiety

A series of thermally stable poly(arylene ether ketone)s (PAEKs) bearing benzimidazole structure in the main chains, named poly(arylene ether ketone‐benzimidazole)s (PAEK‐BIs), were directly synthesized by polycondensation of dimethyl bisphenol, dibenzimidazole bisphenol, and difluorobenzophenones. By systematically varying the amount ratio of two kind of bisphenols, the content of benzimidazole moiety in the backbone was controlled straightforwardly. The prepared amorphous polymers were characterized in terms of Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, thermal, dielectric, and gas transport properties. Evaluation of solubility reveals that PAEK‐BIs with >60% content of benzimidazole units could be soluble in commonly used organic solvents. Also polymers containing content‐tunable benzimidazole show high glass‐transition temperatures (T_g's, 157–319°C) and excellent thermal stability (e.g., temperature of 5% weight loss, above 438°C in air). Dielectric constants of PAEK‐BIs measured at 25°C are all less than 2.66 in the frequency range of 0.1–50 kHz. For dense films, the ideal gas selectivity and permeability coefficients could be compared with that of commercial Ultem 1000 membrane, which indicate that the PAEK‐BIs are potential to be used for gas separation membrane material. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41289.     

Physical and electrochemical behaviors of directly polymerized sulfonated poly(arylene ether ketone sulfone)s proton exchange membranes with different backbone structures

Sulfonated poly(ether ether ketone sulfone) (SPEEKS) and sulfonated poly(ether ether ketone ketone sulfone) (SPEEKKS) copolymers with different degree of sulfonation (DS) were synthesized by aromatic nucleophilic polycondensation of disodium 3,3′‐disulfonate‐4,4′‐dichloro‐diphenylsulfone (SDCDPS), tertbutylhydroquione, and 4,4′‐difluorobenzophenone or 1,4′‐bi(4‐fluorobenzoyl) benzene. Prepared sulfonated copolymers were characterized by Fourier transform infrared spectra, thermogravimetric analysis, and differential scanning calorimetry. The transmission electron microscope was used to investigate the microstructure of membranes. The different distance between two adjacent sulfonic groups in two series of membranes resulted in different physical and electrochemical properties between two kinds of membranes with the same DS. The proton conductivity, ionic exchange capacity and water uptake of SPEEKS membranes were higher than those of SPEEKKS membranes while the mechanical strength of SPEEKS membranes was lower than that of SPEEKKS membranes at the same DS. Moreover, the SPEEKKS membranes with DS equals to 0.8 showed a good combination of a high proton conductivity (0.046 S/cm at 25°C, 0.061 S/cm at 80°C), acceptable water uptake (33–65 wt %), excellent mechanical strength (tensile strength reached 49.7 MPa), and good thermal properties (T_g above 250°C, T_d5% above 300°C). It suggested that this could be a promising membrane for proton exchange membrane fuel cell application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preliminary Results of the Studies on Fractionation of Ytterbium Isotopes in Yb(III)-Acetate/Yb-Amalgam System

ABSTRACT

Preliminary data on the fractionation of ytterbium isotopes in a Yb(III)-acetate/Yb-amalgam exchange system were obtained. The light isotope was preferentially fractionated to the amalgam phase. The values of the unit separation gain per mass difference, ?, were found to be ?00054 for ^176/71Yb and ?00069 for ^176/174Yb. The difference, which amounted to 00015, may be taken as evidence for the occurrence of the so-called “even-odd” effect. It was also found that the chemical isotope shift of ytterbium was mirrored by the optical isotope shift in its atomic spectra.     

Nitrogen-15 Fractionation by Countercurrent Exchange between Liquid N2O3-N2O4 Mixtures and Their Vapor Phases under Pressured Conditions

Abstract

The nitrogen isotope exchange system for ¹⁵N-fractionation consisting of liquid mixtures of N₂O₃ and N₂O₄ and the vapor phase in equilibrium with the liquid (NO/N₂O₃ system) has been studied at temperatures between ?9 and 20°C under various pressures below 4 atm. A countercurrent isotope exchange apparatus and an associated product refluxer system are described. At 15°C the effective separation factor, α_eff, increases from 1.006 at 1 atm to 1.030 at 2.7 atm and levels off thereafter. The observed α_eff values are in good agreement with recent spectroscopic data. The height equivalent of theoretical plate (HETP) correlates well with the linear flow rate of gas phase, showing a dominant diffusion-control of the overall exchange rate. At 15°C the HETP of the NO/N₂O₃ system under 3～4 atm can be smaller by factors of 7 to 10 than that of the Nitrox (NO/HNO₃ exchange) system having the same product rate, rendering the former system a possibility for significantly smaller plant volume.     

Copolymerization of diglycidylether of bisphenol A and bicyclic bis(γ‐lactone)s using rare earth metal triflates as initiators studied with infrared spectroscopy

The thermal cationic curing of mixtures, in various proportions, of diglycidylether of bisphenol A with two substituted condensed bis(γ‐lactone)s initiated using scandium, ytterbium and lanthanum triflates or a conventional boron trifluoride monoethylamine (BF₃·MEA) initiator was investigated. The evolution of the various reactive groups was followed by means of attenuated total reflection Fourier transform infrared spectroscopy. The formation of mono‐spiroorthoesters (monoSOE)s and bis‐spiroorthoesters (bisSOE)s is discussed. The polymerization of bisSOE structures led to the formation of ether–ester–ketone repeat units, which implied the cationic polymerization took place by a tandem reaction. The use of scandium triflate as an initiator led to the highest chemical incorporation of lactone in the network. Moreover, this initiator was the most active, incorporating a higher proportion of lactone in a shorter time. In contrast, the conventional BF₃·MEA initiator incorporated the lowest proportion of bislactone in the cured material. Copyright © 2010 Society of Chemical Industry     

Chromatographic Separation of Calcium Isotopes with Polymer-Bound Ligands

Abstract

Calcium isotopes were enriched in chromatography columns containing the polymer-bound ligands cryptand [2_B22], cryptand [2_B21], and 18-Crown-6. The largest equilibrium single stage separation factor, 1.0039 ± 0.0002 for the calcium 40/44 isotope pair, was found in calcium exchange with cryptand [2_B22]. The largest separation factor found for 18-Crown-6 was 1.0025 ± 0.0003 for the 40/44 isotope pair. The size of the isotope effect was found to be highly dependent on the solvent composition. An iminodiacetate resin ion exchange column yielded small enrichments of calcium isotopes. Calcium 40/44 exchange with the chelating functional group iminodiacetate yielded a small equilibrium separation factor of 1.00011 ± 0.00003, which was more typical of calcium ion exchange isotope effects.

Comparisons of the above chemical systems based on separative power showed crown chemical exchange to be an improvement over cryptand and iminodiacetate exchange. The cryptand system was rendered impractical as a consequence of a slow exchange rate and a resulting large stage residence time contribution to the separative power, on the order of 45 min. The separation factor for the iminodiacetate system was too small for practical applicability.     

Modification of sulfonated poly(ether ether ketone) membranes by impregnation with the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate for proton exchange membrane fuel cell applications

Sulfonated poly(ether ether ketone) (SPEEK) membranes were modified by impregnation with the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMI.BF₄) by immersion into an IL aqueous solution for different periods of time. The modified membranes were investigated by thermogravimetric analyses (TGA), differential scanning calorimetry (DSC), ion exchange capacity (IEC), and conductivity. The SPEEK membrane immersed into the IL aqueous solution for 2 min showed greater dimensional and thermal stability than the pristine SPEEK membrane, and achieved higher decomposition temperatures. It also presented a higher conductivity value (1.0 mS cm^?1), indicating that BMI.BF₄ is a promoter of proton conductivity. The membrane electrode assembly (MEA) produced reached maximum values of power density of 0.13 W cm^?2 and current density of 0.54 A cm^?2 during fuel cell operation. The results indicate that the SPEEK membrane modified by immersion for 2 min is promising for use in a proton exchange membrane fuel cell. Its performance yielded values very close to those obtained with Nafion, which reaches maximum values of power density of 0.19 W cm^?2 and current density of 0.77 A cm^?2. POLYM. ENG. SCI. 56:1037–1044, 2016. © 2016 Society of Plastics Engineers     

FRACTIONATION OF LITHIUM ISOTOPES IN ION EXCHANGE CHROMATOGRAPHY WITH TITANIUM PHOSPHATE EXCHANGER

ABSTRACT

Ion exchange chromatography of lithium was carried out to study the lithium isotope effect in an aqueous ion-exchange system, using titanium phosphate exchangers granulated with polyvinyl chloride or an inorganic binder. The sample granulated with PVC showed significant isotope fractionations when a 0.05 M (NH₄)₂CO₃ solution was used as an eluent. The lighter isotope ⁶Li was preferentially fractionated into the exchanger phase. The isotope separation factor was roughly evaluated as 1.007, which is smaller than that (1.017) obtained by batch experiment in a preceding paper. The smaller separation factor could be explained by the fact that the number of sites effective for Li⁺ exchange is less than the number evaluated from the ion exchange capacity. The exchanger granulated with an inorganic binder did not show lithium isotope fractionation in spite of its large capacity for retention of lithium.     

Synthesis and properties of copolymers of poly(ether ketone ketone) and poly(ether amide ether amide ether ketone ketone)

Poly(aryl ether ketone)s (PAEKs) are a class of high‐performance engineering thermoplastics known for their excellent combination of chemical, physical and mechanical properties, and the synthesis of semicrystalline PAEKs with increased glass transition temperatures (T_g) is of much interest. In the work reported, a series of novel copolymers of poly(ether ketone ketone) (PEKK) and poly(ether amide ether amide ether ketone ketone) were synthesized by electrophilic solution polycondensation of terephthaloyl chloride with a mixture of diphenyl ether and N,N′‐bis(4‐phenoxybenzoyl)‐4,4′‐diaminodiphenyl ether (BPBDAE) under mild conditions. The copolymers obtained were characterized using various physicochemical techniques. The copolymers with 10–35 mol% BPBDAE are semicrystalline and have markedly increased T_g over commercially available poly(ether ether ketone) and PEKK due to the incorporation of amide linkages in the main chain. The copolymers with 30–35 mol% BPBDAE not only have high T_g of 178–186 °C, but also moderate melting temperatures of 335–339 °C, having good potential for melt processing. The copolymers with 30–35 mol% BPBDAE have tensile strengths of 102.4–103.8 MPa, Young's moduli of 2.33–2.45 GPa and elongations at break of 11.7–13.2%, and exhibit high thermal stability and good resistance to organic solvents. Copyright © 2010 Society of Chemical Industry     

Epoxy resin cure. I. Fluorine-19 NMR of boron trifluoride monoethylamine and fluoroboric acid

Fluorine-19 NMR is used to examine the role of boron trifluoride monoethylamine (BF₃–MEA) in epoxy resin cure. Spectra were first recorded in a variety of solvents suitable for dissolving different epoxy resins. All spectra contained a peak due to fluoroboric acid. Spectra of BF₃–MEA in orthodichlorobenzene were then recorded at elevated temperatures. The floroboric acid peak area increased, indicating that the BF₃–MEA was being hydrolyzed. Results indicate that, at temperatures above 100°C, BF₃–MEA is completely hydrolyzed within 5 min to fluoroboric acid.     

Identification of some boron-based curing agents in cured epoxy systems by computer-assisted infrared spectroscopy

The use of computer-assisted infrared spectroscopy has allowed identification of three different boroxines and a boron trifluoride complex used as curing agents in cured epoxy resins. Boroxines were distinguished from a boron trifluoride complex by the B? O stretch absorption near 1400 cm^?1 in the solid state. Detection of this absorption was enhanced by spectral subtraction methods in which the reference spectrum was that of the parent resin, or a suitably cured system of similar structure. Distinction between different boroxines was achieved by analysis of the gases evolved from samples heated at 300°C in nitrogen. Identification of the alcohol fraction of the original boroxine was improved by subtraction of the spectrum of water vapor. Boron trifluoride was detected in the gases evolved at 450–500°C from BF₃-cured systems, and also in the liquid pyrolyzates. Further simplification of the 300°C gas spectra by subtraction of alcohol and carbon dioxide revealed the presence of acrolein in the gases from boroxine-cured systems while BF₃-cured systems yielded acetaldehyde. These differences may be associated with different end groups in the cured resins.     

Synthesis and properties of novel copolymers of poly(ether ketone ether ketone ketone) and poly(ether ketone ketone ether ketone ketone) containing 1,4‐naphthylene moieties

A new monomer, 1,4‐bis(4‐phenoxybenzoyl)naphthalene (BPOBN), was conveniently synthesized via a simple synthetic procedure from readily available materials. A series of novel copolymers of poly(ether ketone ether ketone ketone) and poly(ether ketone ketone ether ketone ketone) containing 1,4‐naphthylene moieties were prepared by the Friedel‐Crafts acylation solution copolycondensation of terephthaloyl chloride (TPC) with a mixture of BPOBN and 4,4′‐diphenoxybenzophenone (DPOBPN), over a wide range of BPOBN/DPOBPN molar ratios, in the presence of anhydrous AlCl₃ and N‐methylpyrrolidone in 1,2‐dichloroethane. The copolymers with 10–40% BPOBN are semicrystalline and had remarkably increased T_gs over the conventional PEEK and PEKK due to the incorporation of 1,4‐naphthylene moieties in the main chains. The copolymers with 30–40 mol% BPOBN had not only high T_gs of 176–177°C, but also moderate T_ms of 332–338°C, which are suitable for the melt processing. These polymers had tensile strengths of 101.5–104.7 MPa, Young's moduli of 2.49–2.65 GPa, and elongations at break of 13.3–15.7% and exhibited high thermal stability and excellent resistance to organic solvents. POLYM. ENG. SCI., 56:566–572, 2016. © 2016 Society of Plastics Engineers     

Synthesis and characterization of novel sulfonated poly(arylene ether ketone)s derived from 4,4'-sulfonyldiphenol

Summary Novel sulfonated poly(arylene ether ketone)s were prepared directly by aromatic nucleophilic polycondensation of 4,4'-sulfonyldiphenol with various ratios of 4,4'-difluorobenzophenone to 5,5'-carbonylbis(2-fluorobenzenesulfonate) in dimethyl sulfoxide. The resulting polyelectrolytes were characterized by IR, NMR, TGA and DSC. The 10% weight loss temperature of the products is higher than 510°C, and their glass transition temperature is above 260°C. The introduction of 4,4'-sulfonyldiphenol with powerful electron-withdrawing group, -SO₂₋, into the main chain of sulfonated poly(arylene ether ketone)s improves the thermal stability against desulfonation. The ion-exchange capacity and swelling of the polyelectrolyte membranes were measured, which are higher than 1.23meq/g and not higher than 20.9%, respectively. The membranes show very good perspectives in polymer electrolyte fuel cell (PEMFC) application. Received: 27 March 2002 / Revised version: 7 May 2002 / Accepted: 13 May 2002     

Synthesis and properties of novel copolymers of poly(ether ketone diphenyl ketone ether ketone ketone) and poly(ether amide ether amide ether ketone ketone)

New monomers, 4,4′‐bis(4‐phenoxybenzoyl)diphenyl (BPOBDP) and N,N′‐bis(4‐phenoxybenzoyl)?4,4′‐diaminodiphenyl ether (BPBDAE), were conveniently synthesized via simple synthetic procedures from readily available materials. Novel copolymers of poly(ether ketone diphenyl ketone ether ketone ketone) (PEKDKEKK) and poly(ether amide ether amide ether ketone ketone) (PEAEAEKK) were synthesized by electrophilic Friedel‐Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of BPOBDP and BPBDAE, over a wide range of BPOBDP/BPBDAE molar ratios, in the presence of anhydrous AlCl₃ and N‐methylpyrrolidone (NMP) in 1,2‐dichloroethane (DCE). The copolymers obtained were characterized by different physico‐chemical techniques. The copolymers with 10–40 mol% BPBDAE are semicrystalline and had remarkably increased T_gs over commercially available PEEK and PEKK due to the incorporation of amide and diphenyl linkages in the main chains. The copolymers IV and V with 30–40 mol% BPBDAE had not only high T_gs of 185–188°C, but also moderate T_ms of 326–330°C, having good potential for the melt processing. The copolymers IV and V had tensile strengths of 101.7–102.3 MPa, Young's moduli of 2.19–2.42 GPa, and elongations at break of 13.2–16.6% and exhibited high thermal stability and excellent resistance to organic solvents. POLYM. ENG. SCI., 54:1757–1764, 2014. © 2013 Society of Plastics Engineers