Aqueous Solvent Systems Research Articles

Stirred and non-stirred lignin solvolysis with formic acid in aqueous and ethanolic solvent systems at different levels of loading in a 5-L reactor

Lignin polymer is biologically and chemically stable and requires highly vigorous conditions for de-polymerization, and subsequent stabilization of the monomeric conversion products to prevent re-polymerization and char production. The Lignin-to-Liquid (LtL) process is a solvolytic conversion of lignin with formic acid. Formic acid has been shown to both catalyze the de-polymerization and supply hydrogen that stabilizes the de-polymerization products. In this paper, lignin from Eucalyptus wood was used as the feedstock, and the LtL-process was performed in both aqueous and ethanolic solvent systems. The experimental variables were different levels of loading in the reactor, stirred and non-stirred conditions, and different reaction temperatures. The bio-oil consisted mostly of phenolic compounds, and the bio-oil yields differed with type of the solvent used, level of loading in the reactor, stirring condition, and operating temperature. More than 55 wt.% of the lignin was recovered as bio-oil at 320 °C at stirred conditions when the reactor was loaded at high level. Overall, the ethanolic solvent together with maximum level of loading in the reactor under stirred condition resulted in the highest bio-oil yield. Elemental balance data for bio-oil and char yields and the molecular composition of the bio-oils were also investigated using, respectively, elemental analysis and GC-MS. Finally, principal component analysis was used as well to systematically explore the relationship between the bio-oil and char yields and the reaction conditions.

NaN3 Catalyzed Highly Convenient Access to Functionalized 4H-chromenes: A Green One-pot Approach for Diversity Amplification

An energy efficient, one-pot synthetic method has been described for the access of biologically privileged tetrahydro-4H-chromene derivatives via Knoevenagel condensation and Michael additions of various aldehydes with malononitrile and dimedone in aqueous ethanol solvent system. Good chemical yields were obtained in relatively shorter reaction times under mild conditions using sodium azide as a commercially accessible, inexpensive and less-toxic catalyst. Easy isolation of products, high atom-economy, environmental benignity and applicability to gram scale synthesis are the prominent features of this protocol.

ASSESSMENT OF CORROSION INHIBITORY EFFECT OF Ruta chalepensis FLAVONOID EXTRACTS ON API 5L X52 STEEL IN 1M HCL MEDIUM

The development of green eco-friendly inhibitors for the corrosion of metallic surfaces in acid media is still considered as a major challenge and target for corrosion-mitigation engineers. We have prepared in this work 4 different extracts from the plant Ruta Chalepensis using methanol, chloroform, ethyl acetate, and aqueous ethyl acetate solvent systems. The flavonoids content, as well as the other oxygenated compounds, in the 4 extracts was carefully screened using the gas chromatographic mass spectrometry (GC-MS) technique. The corrosion inhibition property of all extracts for API 5L X52 steel in the hydrochloric acid medium has been carefully assessed using electrochemical techniques and surface-morphological characterizations. Our results revealed promising corrosion-inhibition properties for the methanol and chloroform extracts compared to other extracts and suggest potential applicability for the flavonoids from the studied plant as green corrosion inhibitors for steel substrates in acid media.

Effects of dope compositions on morphologies and separation performances of PMDA-ODA polyimide hollow fiber membranes in aqueous and organic solvent systems

Hollow fibers (HFs) fabricated with organo-insoluble polyimides are rarely adopted in the application of organic solvent nanofiltration (OSN), since the insolubility limits their processability. To deal with it, its precursor polyamic acid (PAA) is selected to fabricate HFs, but the slow phase inversion nature of PAA may lead to filament breaking during spinning. In an earlier study, we have successfully addressed the processing of spinning PMDA-ODA PAA HFs with regular cross-sections, but the membrane’s separation performances is not shown. Here for optimal performances, we investigate the effects of dope compositions including polymer concentration, ethanol (EtOH) and TiO2 additives on the pore size and pore size distributions, hydrophilicities, and separation properties of PMDA-ODA PI HF membranes in both aqueous and organic solvent systems. The results showed that polymer dopes with high concentrations of PAA or EtOH led to high rejections but sacrificing permeability. Interestingly, just adding 1.1 wt% TiO2 in dope solutions significantly increased membrane porosities, hydrophilicities and decreased membrane surface charges. Therefore, membrane water fluxes were doubled and rejections to negatively charged dyes increased. At last, the PMDA-ODA PI HF membranes showed good separation performance in organic solvents also. The optimal permeability and rejection in DMF solution was 2.51 L m−2 h−1 bar−1 and 90.6% for FG (Fast Green, MW = 808 Da) dye. Hence, the PMDA-ODA PI HF membranes are suitable for applications in both aqueous and organic systems.

The use of chromium(III) complexes to enhance peptide protonation by electrospray ionization mass spectrometry.

The addition of trivalent chromium, Cr(III), reagents to peptide solutions can increase the intensity of doubly protonated peptides, [M+2H]2+ , through electrospray ionization (ESI). Three model heptapeptides were studied: neutral (AAAAAAA), acidic (AAEEEAA), and basic (AAAKAAA). The neutral and acidic peptides form almost no 2+ ions in the absence of Cr(III). Twenty Cr(III) complexes were used as potential enhanced protonation reagents, including 11 complexes with nonlabile ligands and nine with labile ligands. The complexes that provide the most abundant [M+2H]2+ , the greatest [M+2H]2+ to [M+H]+ ratio, and the cleanest mass spectra are [Cr(H2 O)6 ](NO3 )3 ·3H2 O and [Cr(THF)3 ]Cl3 . Anions in Cr(III) reagents can also affect the intensity of [M+2H]2+ and the [M+2H]2+ to [M+H]+ ratio through cation-anion interactions. The influence of anions on the extent of peptide protonation follows the trend ClO4 - ˃SO4 2- ˃Br- ˃Cl- ˃F- ≈NO3 - . Solvent effects and complexes with varying number of water ligands were investigated to study the importance of water in enhanced protonation. Aqueous solvent systems and Cr(III) complexes that have at least one bound water ligand in solution must be used for successful increase in the intensity of [M+2H]2+ , which indicates that water is involved in the mechanism of Cr(III)-induced enhanced protonation. The ESI source design is also important because no enhanced protonation was observed using a Z-spray source. The current results suggest that this Cr(III)-induced effect occurs during the ESI desolvation process.

Volumetric, isentropic compressibility and viscosity coefficient studies of binary solutions involving amides as a solute in aqueous and CCl4 solvent systems at 298.15 K

The experimental measurements of the density, speed of sound and viscosity coefficient in binary solutions involving water and CCl4 as solvents and formamide, N-methylformamide, N, N-dimethylformamide, N-methylacetamide and N, N-dimethylacetamide as solute in the concentration range (0.00992 mol·kg−1 to 1.07890 mol·kg−1) at 298.15 K are reported. The data are used to obtain the isentropic compressibility (βs) of solutions and Jones-Dole viscosity B and D coefficients for solutes. The derived properties like apparent molar volume (Vϕ) and apparent molar isentropic compressibility (Kϕ) of amides at different concentrations are evaluated. The data of limiting apparent molar volume (Vϕ0) and apparent molar isentropic compressibility (Kϕ0) for amides in both solvent systems (H2O and CCl4) and their concentration variation are examined to study the effect of intermolecular H-bond formation (for the amide molecules), hydrophobic interaction effect in water and amide-CCl4 interactions. It has been observed that there is loss of volume and compressibility of amide molecules in transferring them from pure liquid state to water and gain in transferring to CCl4 solutions (non-aqueous solvent) except for dimethylacetamide. The transfer volumes and compressibilities from CCl4 to water are negative and are attributed to H bond formation between solute molecules. The viscosity B coefficients for the amides are found to be high positive in water while they are of small magnitude in CCl4 medium. All these results are discussed on the basis of solute-solvent interaction, hydrophobic interaction in water and H-bond formation possibilities in CCl4. It is proposed that, the dissolution of dimethylformamide in water takes place substitutionally in water cavities with very little volume change.

Comment on “Measurement and Correlation of the Solubility of 2,6-Dihydroxybenzoic Acid in Alcohols and Binary Solvents”

The experimental solubility data of 2,6-dihydroxybenzoic acid in neat organic solvents and binary aqueous solvent systems at temperature range from (278.15 to 318.15) K have carefully been reanalyzed and some recommendations were proposed. In addition, a combined form of the Jouyban–Acree–van’t Hoff model and the Abraham solvation parameters was used to predict the solubility of 2,6-dihydroxybenzoic acid in the binary solvent mixtures at various temperatures.

Phase equilibria and the surface tension of polypropylene polyol series in water/methanol mixtures: A consideration of structural effects

The phase equilibria and surface tension of a polypropylene polyol (PPP) series was studied in aqueous solvent systems. The PPP series was composed of ethylene oxide (EO) and propylene oxide (PO) groups, exhibiting specific interactions with both water and alcohols. Binary and ternary liquid-liquid equilibria (LLE) of the PPP series were determined via thermo-optical analysis (TOA) methods, which represented closed-loop miscibility in water and Treybal Type 1 behavior in water and methanol (MeOH), respectively. The surface tension of the ternary PPP1/water/MeOH system was measured using a well-known plate method. The dendritic characteristics of the PPP series were reflected through modeling using lattice cluster theory (LCT) for complex structures of the polymer. The phase diagrams and surface tension of the PPP series were described from binary to ternary systems based on LCT incorporated with Guggenheim's treatment using predetermined parameters. The calculated results of both systems were in good agreement with the experimental data using the same interaction energy parameters.

Structure refinement of membrane proteins via molecular dynamics simulations.

A refinement protocol based on physics-based techniques established for water soluble proteins is tested for membrane protein structures. Initial structures were generated by homology modeling and sampled via molecular dynamics simulations in explicit lipid bilayer and aqueous solvent systems. Snapshots from the simulations were selected based on scoring with either knowledge-based or implicit membrane-based scoring functions and averaged to obtain refined models. The protocol resulted in consistent and significant refinement of the membrane protein structures similar to the performance of refinement methods for soluble proteins. Refinement success was similar between sampling in the presence of lipid bilayers and aqueous solvent but the presence of lipid bilayers may benefit the improvement of lipid-facing residues. Scoring with knowledge-based functions (DFIRE and RWplus) was found to be as good as scoring using implicit membrane-based scoring functions suggesting that differences in internal packing is more important than orientations relative to the membrane during the refinement of membrane protein homology models.

Hydroaminomethylation in Aqueous Solvent Systems – An Efficient Pathway to Highly Functionalized Amines

AbstractTandem‐catalyzed hydroaminomethylation is a useful tool for synthesizing linear amines from olefins and amines in an atom‐efficient manner. To enable the coupling of highly functionalized, hydrosoluble amines with non‐water‐soluble olefins, this reaction must be transferred to aqueous biphasic solvent systems. In this work, we systematically evaluate reaction conditions to provide a selective hydroaminomethylation of 1‐octene with diethanolamine as model substrates. Although water is both the condensation side product and the solvent, yields of 79% were achieved using a catalytic system consisting a rhodium precursor and a sulfonated diphosphine ligand. This approach was applied to other functionalized amines, proving this concept is a suitable tool for the catalytic alkylation of highly functionalized amines.magnified image

Oxygen sensitive polymeric nanocapsules for optical dissolved oxygen sensors

Immobilization of the oxygen-sensitive probes (OSPs) in the host matrix greatly impacts the performance and long-term usage of the optical dissolved oxygen (DO) sensors. In this work, fluorescent dyes, as the OSPs, were encapsulated with a crosslinked fluorinated polymer shell by interfacial confined reversible addition fragmentation chain transfer miniemulsion polymerization to fabricate oxygen sensitive polymeric nanocapsules (NCs). The location of fluorescent dyes and the fluorescent properties of the NCs were fully characterized by fourier transform infrared spectrometer, x-ray photoelectron spectrometer and fluorescent spectrum. Dye-encapsulated capacity can be precisely tuned from 0 to 1.3 wt% without self-quenching of the fluorescent dye. The crosslinked fluorinated polymer shell is not only extremely high gas permeability, but also prevents the fluorescent dyes from leakage in aqueous as well as in various organic solvents, such as ethanol, acetone and tetrahydrofuran (THF). An optical DO sensor based on the oxygen sensitive NCs was fabricated, showing high sensitivity, short response time, full reversibility, and long-term operational stability of online monitoring DO. The sensitivity of the optical DO sensor is 7.02 (the ratio of the response value in fully deoxygenated and saturated oxygenated water) in the range 0.96–14.16 mg l−1 and the response time is about 14.3 s. The sensor’s work curve was fit well using the modified Stern–Volmer equation by two-site model, and its response values are hardly affected by pH ranging from 2 to 12 and keep constant during continuous measurement for 3 months. It is believed that the oxygen sensitive polymeric NCs-based optical DO sensor could be particularly useful in long-term online DO monitoring in both aqueous and organic solvent systems.

Towards a process for the telomerization of butadiene with N-methylglucamine

The telomerization of 1,3-dienes with functionalized nucleophiles presents an atom efficient and selective synthesis of potential non-ionic surfactants. Crucial for application of these synthetic pathways is the effective recycling of the homogeneous palladium catalyst. In this work, we present the telomerization of 1,3-butadiene with the renewable aminopolyol N-methylglucamine to a non-ionic surfactant in an aqueous solvent system. In order to achieve phase separation, the addition of freshly added 1,3-butadiene instead of an additional solvent offers an elegant way of catalyst recycling. With this method, recycling of the catalyst is feasible; a total turnover number of 1456 was reached.

Characterization of a prodigiosin synthetase PigC from Serratia marcescens jx-1 and its application in prodigiosin analogue synthesis

Due to their diverse bioactive effects, prodigiosin and its analogues (prodiginines) have attracted a great deal of attention. In this study, a prodigiosin synthetase PigC catalyzing a condensation reaction to produce prodigiosin was cloned from Serratia marcescens jx-1 and overexpressed in Escherichia coli with a putative polypeptide of 888 amino acids. Its biochemical properties and applications in prodiginines synthesis were investigated. The purified enzyme had a specific activity of 6.96 U/mg and exhibited optimal activity at 10 °C and pH 7.5. The recombinant PigC performed good stability below 30 °C and at pH ranging from 6.0 to 8.5. This enzyme was activated by Ca2+, while inhibited by Cu2+. The kinetic analysis with 4-methoxy-2,2′-bipyrrole-5-carboxyaldehyde (MBC) and 2,4-dimethyl-3-ethylpyrrole (DMEP) as substrates yielded apparent Km of 23.4 and 4.2 μmol/L, respectively. The enzymatic catalysis using whole cells of recombinant E. coli harboring the PigC as catalyst in an aqueous organic solvent system resulted in 59.4% yield of prodigiosin analogues, which exhibited excellent antimicrobial properties against Staphylococcus aureus, Bacillus subtilis and E. coli. The results obtain here demonstrated the great potential of PigC for the biosynthesis of prodigiosin and its analogues.

Cellulose films from the aqueous DMSO/TBAH-system

Regulation of pore defects is the critical technique for obtaining good performance of the cellulosic films. In this work, we have proved that the introduction of dimethyl sulfoxide into the new aqueous solvent system of tetrabutylammonium hydroxide can remarkably promote the dissolving capability of the natural cellulose. It is interesting to found that a suitable gelation during the aging process in preparing the cellulose films is very benefit for the mechanical performance of the prepared material. The relationship among process, structure and performance of the cellulose films has been researched. WAXD and FT-IR analysis have revealed the composition of cellulose II and IVII. The formed cellulose IVII with the structural characteristic of gel-like during the aging (gelation) process can serve as the uniform framework for heterogeneous regeneration of cellulose II, with which a cellulose films of network-like, good homogeneity and defect-free can be prepared. And synchronous enhancements of the tensile strength by 75% (from 78 to 137 MPa) and the elongation at break by 155% (from 4.63 to 11.80%) have been realized. The initial investigation in this work provides a sustainable approach to developing a facile process for high-performance materials from the natural cellulose.

Room temperature synthesis of polyvinyl alcohol stabilized palladium nanoparticles: Solvent effect on shape and electro-catalytic activity

Palladium nanoparticles have been synthesized at room temperature, 25±.5°C by the reduction of K2PdCl4 using biocompatible polymer polyvinyl alcohol (PVA) as reducing and stabilizing agent in water and aqueous dimethyl formamide (DMF) media with varying composition of DMF. The effect of variation of composition of aqueous DMF on growth, morphology and size of palladium nanocrystals is explained. Different aqueous DMF mixtures furnish palladium nanoparticles of different shapes like triangular plates, cuboids, hexagon with different average edge length between (3–30 nm) indicating preferential interaction and blocking of DMF to some specific planes of nanocrystals leading to various shapes. The synthesized nanoparticles have been characterized by different spectroscopic, microscopic and electro-analytical studies like cyclic voltammetry (CV), chronopotentiometry (CP) and chronoamperometry (CA). The increase in electro-catalytic activity is found to decrease with the increased size of the embedded crystallites deposited on the support constituting the electrodes and hence on the precursor medium. The same order of the studied electrodes is found from mole normalized peak current density values (Amol−1Pd) in CV, transition time in CP and steady current density values in CA, on increasing the content of DMF in the aqueous DMF solvent system as expected. The outcomes are explained on the basis of the crystallite size, morphology of the surface, unequal development of certain planes and purity of the products as guided by the rate of nucleation and growth of the particles formed in different media.

Solubility of Etoricoxib in Aqueous Solutions of Glycerin, Methanol, Polyethylene Glycols 200, 400, 600, and Propylene Glycol at 298.2 K

Experimental molar solubility of etoricoxib (ETR) in monosolvents such as glycerin, methanol (MeOH), polyethylene glycol 200 (PEG 200), polyethylene glycol 400 (PEG 400), polyethylene glycol 600 (PEG 600), propylene glycol (PG), and their aqueous binary solvent systems in various mass fraction compositions along with the solute-free and saturated solution densities were measured at 298.2 K. The resulting mole fraction solubility and density data were further correlated and predicted with the Jouyban–Acree model. Overall mean percentage deviations (OMPDs) between experimental and calculated mole fraction solubilities were 3.5%. The solute-free density of the monosolvents and their aqueous binary solvent systems were employed to train the model and then the densities of the saturated solutions were predicted. Moreover, OMPDs for back calculated solute-free densities and predicted saturated solution densities were 0.07% and 0.40%, respectively. Thus, the Jouyban–Acree model have potential use in preformulati...

Solvent Development for Post-Combustion CO2 Capture: Recent Development and Opportunities

Chemical absorption is widely regarded as the most promising technology for post-combustion CO2 capture from large industrial emission sources with CO2 separation from natural gas using aqueous amine solvent system having been applied since the 1930s. The use of monoethanolamine (MEA) in CO2 absorption system possesses several drawbacks, such as high regeneration energy, high solvent loss, and high corrosion tendency. Various solvents have been developed for post-combustion CO2 capture application including the development of aqueous solvents and phase-change solvents. Some of these alternate solvents have been reported to have better solvent properties, which could improve the CO2 absorption system performance. This paper reviews key parameters involved in the design improvement of several chemical absorption process systems. In addition, some novel solvent systems are also discussed, for example encapsulated solvents systems. Some of the key solvent parameters that affect the capture performance, such as heat of reaction, absorption rate, solvent working capacity, solvent concentration, and solvent stability, are discussed in this paper, particularly in relation to the economic viability of the capture process. In addition, some guidelines for the future solvent development are discussed.

Thermodynamic Parameters of the Dissolution of 4-Hydroxy-L-Proline and L-Phenylalanine in Mixed Aqueous Solvents at 298 K

The enthalpies of solution of 4-hydroxy-L-proline and L-phenylalanine in binary mixed aqueous solvents containing acetonitrile (AN), 1,4-dioxane (1,4-DO), or acetone (AC) at mole fractions of 0 to 0.25 are determined at T = 298.15 K via isothermal calorimetry. The standard enthalpies of solution (ΔsolH°) and transfer (ΔtrH°) of 4-hydroxy-L-proline and L-phenylalanine from water to mixed aqueous solvents are calculated using the experimental calorimetric data, as are the enthalpy coefficients of paired interactions (h xy ) between the molecules of the investigated amino acids and the organic solvents. The effects the mixed aqueous solvent composition and the structure of the organic solvent molecules have on the enthalpies of solution and transfer for the investigated amino acids are considered. The correlation between the enthalpy of solution of the amino acids and the electron-donating properties of the organic solvents in the mixed aqueous solvent systems is established.

Current State of Art of Diaminomalenonitrile Based Synthetic Receptors for Ion Sensing With Bio Applications: Mechanistic, Sensing and Photophysical Aspects

To the best of our knowledge, only a few number of single molecule based receptors synthesized from Diaminomalenonitrile (DAMN) have been explored and developed as highly selective and sensitive recognition motifs for cations and anions in a organic, aqueous or mixed solvent system. The interaction between such receptors and ions has been reported with remarkable alteration in absorption and fluorescence properties of the molecule. The signal transduction is prompt, and attributed to the modulation of Internal Charge Transfer (ICT) and/or Photo Induced Electron Transfer (PET) processes within the molecule. In this review, we have compiled whole literature about recognition of ions via DAMN based molecular receptors possessing biological applications including live cell imaging. Emphasis has been diverted to summarize and briefly discuss signal response, operation of solvent, selectivity, binding affinity and detection limit. In addition to this, some of the crucial design considerations, such as choice of fluorophore, tuning of electronic effects and mechanism of operation are momentarily discussed.

Screening the effect of four ultrasound-assisted extraction parameters on hesperidin and phenolic acid content of aqueous citrus pomace extracts

Polyphenols of citrus by-products, due to their antioxidant and antimicrobial activities, could be valorized by pharmaceutical and food industries, adding a value to the citrus processing companies. A number of studies have investigated the effect of ultrasound-assisted extraction (UAE) conditions on the recovery of phenolics derived from citrus waste using both organic solvents or mixed aqueous solvent systems. To maximize efficiency, UAE conditions should be tailored to the physical parameters of the solvent(s) employed. The aim of this study was to investigate the effect of four UAE parameters: particle size (1.40–2.80 mm), extraction time (10–60 min), extraction temperature (23–50 °C) and ultrasonic power (150–250 W) on the simultaneous recovery of p-coumaric acid, caffeic acid, chlorogenic acid, and hesperidin from citrus waste using pure water as a solvent. High-performance liquid chromatography (HPLC) was employed for the identification and quantification of the cited compounds. Particle size was determined to be an important parameter affecting compound recovery, with the exception of chlorogenic acid. A particle size of 1.40 mm resulted in the highest recovery of p-coumaric and caffeic acids (0.25 and 0.58 mg/g, respectively), while higher hesperidin yields were achieved from the particle sizes of 2.00 and 1.40 mm (6.44 and 6.27 mg/g, respectively). Extraction temperature significantly affected only the recovery of the flavanone glycoside (P < 0.05). As the extraction temperature increased from 30 to 50 °C the recovery of hesperidin increased from 6.59 to 7.84 mg/g, respectively. Neither extraction time nor ultrasonic power significantly affected the recovery of any individual phenolic compound.