Showing papers on "Solvent published in 2015"

Water – A magic solvent for biomass conversion

Abstract: Hydrothermal biomass conversion processes provide the opportunity to use feedstocks with high water content for the formation of energy carriers or platform chemicals. The water plays an active role in the processes as solvent, reactant and catalyst or catalyst precursor. In this paper, the different hydrothermal processes of carbonization, gasification and liquefaction are introduced and the specific role of water is discussed for each of them. The high reactivity of the polar components of biomass in hot compressed water and its changing properties with temperature are the key to obtain high selectivities of the desired products. Despite the obvious advantages of hydrothermal conversion examples for industrial applications are rare. The main reason for not commercial application of water in the high temperature state is that there are no products that can be sold with profit and cannot be produced cheaper, with less capital risk, and with more simple processes.

Room temperature synthesis of covalent-organic framework films through vapor-assisted conversion.

Abstract: We describe the facile synthesis of several two-dimensional covalent–organic frameworks (2D COFs) as films by vapor-assisted conversion at room temperature. High-quality films of benzodithiophene-containing BDT-COF and COF-5 with tunable thickness were synthesized under different conditions on various substrates. BDT-COF films of several micrometer thickness exhibit mesoporosity as well as textural porosity, whereas thinner BDT-COF films materialize as a cohesive dense layer. In addition, we studied the formation of COF-5 films with different solvent mixture compositions serving as vapor source. Room temperature vapor-assisted conversion is an excellent method to form COF films of fragile precursors and on sensitive substrates.

Defect-free Naphthalene Diimide Bithiophene Copolymers with Controlled Molar Mass and High Performance via Direct Arylation Polycondensation.

Abstract: A highly efficient, simple, and environmentally friendly protocol for the synthesis of an alternating naphthalene diimide bithiophene copolymer (PNDIT2) via direct arylation polycondensation (DAP) is presented. High molecular weight (MW) PNDIT2 can be obtained in quantitative yield using aromatic solvents. Most critical is the suppression of two major termination reactions of NDIBr end groups: nucleophilic substitution and solvent end-capping by aromatic solvents via C–H activation. In situ solvent end-capping can be used to control MW by varying monomer concentration, whereby end-capping is efficient and MW is low for low concentration and vice versa. Reducing C–H reactivity of the solvent at optimized conditions further increases MW. Chain perfection of PNDIT2 is demonstrated in detail by NMR spectroscopy, which reveals PNDIT2 chains to be fully linear and alternating. This is further confirmed by investigating the optical and thermal properties as a function of MW, which saturate at Mn ≈ 20 kDa, in agr...

Graphene oxide immobilized enzymes show high thermal and solvent stability.

Abstract: The thermal and solvent tolerance of enzymes is highly important for their industrial use. We show here that the enzyme lipase from Rhizopus oryzae exhibits exceptionally high thermal stability and high solvent tolerance and even increased activity in acetone when immobilized onto a graphene oxide (GO) nanosupport prepared by Staudenmaier and Brodie methods. We studied various forms of immobilization of the enzyme: by physical adsorption, covalent attachment, and additional crosslinking. The activity recovery was shown to be dependent on the support type, enzyme loading and immobilization procedure. Covalently immobilized lipase showed significantly better resistance to heat inactivation (the activity recovery was 65% at 70 °C) in comparison with the soluble counterpart (the activity recovery was 65% at 40 °C). Physically adsorbed lipase achieved over 100% of the initial activity in a series of organic solvents. These findings, showing enhanced thermal stability and solvent tolerance of graphene oxide immobilized enzyme, will have a profound impact on practical industrial scale uses of enzymes for the conversion of lipids into fuels.

Subtle Balance Between Length Scale of Phase Separation and Domain Purification in Small‐Molecule Bulk‐Heterojunction Blends under Solvent Vapor Treatment

Abstract: A series of solvents with different solubilities for DR3TBDTT and PC71 BM, and different boiling points, is used for solvent vapor annealing (SVA) treatment to systematically investigate the solvent-morphology-performance relationship. The presence of solvent molecules inside bulk-heterojunction (BHJ) thin films promotes the mobility of both donor and acceptor molecules, leading to crystallization and aggregation, which are important in modulating morphology.

Comparison of Cell Disruption Methods for Improving Lipid Extraction from Thraustochytrid Strains

Abstract: Lipid extraction is an integral part of biodiesel production, as it facilitates the release of fatty acids from algal cells. To utilise thraustochytrids as a potential source for lipid production. We evaluated the extraction efficiency of various solvents and solvent combinations for lipid extraction from Schizochytrium sp. S31 and Thraustochytrium sp. AMCQS5-5. The maximum lipid extraction yield was 22% using a chloroform:methanol ratio of 2:1. We compared various cell disruption methods to improve lipid extraction yields, including grinding with liquid nitrogen, bead vortexing, osmotic shock, water bath, sonication and shake mill. The highest lipid extraction yields were obtained using osmotic shock and 48.7% from Schizochytrium sp. S31 and 29.1% from Thraustochytrium sp. AMCQS5-5. Saturated and monounsaturated fatty acid contents were more than 60% in Schizochytrium sp. S31 which suggests their suitability for biodiesel production.

Preparation of macroporous alginate-based aerogels for biomedical applications

Abstract: Aerogels are a special class of ultra-light porous materials with growing interest in biomedical applications due to their open pore structure and high surface area However, they usually lack macroporosity, while mesoporosity is typically high In this work, carbon dioxide induced gelation followed by expansion of the dissolved CO2 was performed to produce hybrid calcium-crosslinked alginate-starch hydrogels with dual meso- and macroporosity The hydrogels were subjected to solvent exchange and supercritical drying to obtain aerogels Significant increase in macroporosity from 2 to 25% was achieved by increasing expansion rate from 01 to 30 bar/min with retaining mesoporosity (BET surface and BJH pore volume in the range 183–544 m2/g and 20–68 cm3/g, respectively) In vitro bioactivity studies showed that the alginate-starch aerogels are bioactive, ie they form hydroxyapatite crystals when immersed in a simulated body fluid solution Bioactivity is attributed to the presence of calcium in the matrix The assessment of the biological performance showed that the aerogels do not present a cytotoxic effect and the cells are able to colonize and grow on their surface Results presented in this work provide a good indication of the potential of the alginate-starch aerogels in biomedical applications, particularly for bone regeneration

Cyanide Single-Molecule Magnets Exhibiting Solvent Dependent Reversible “On” and “Off” Exchange Bias Behavior

Abstract: The syntheses, structures, and magnetic properties of four new complex salts, (PPN){[MnIII(salphen)(MeOH)]2[MIII(CN)6]}·7MeOH (Mn2M·7MeOH) (M = Fe, Ru, Os and Co; PPN+ = bis(triphenylphosphoranylidene)ammonium cation; H2salphen = N,N′-bis(salicylidene)-1,2-diaminobenzene), and a mixed metal Co/Os analogue (PPN){[MnIII(salphen)(MeOH)]2[CoIII0.92OsIII0.08(CN)6]}·7MeOH were undertaken. It was found that all compounds exhibit switchable single-molecule magnet (SMM) and exchange-bias behavior depending on the interstitial methanol content. The pristine (PPN){[Mn(salphen)(MeOH)]2[Os(CN)6]}·7MeOH (Mn2Os·7MeOH) behaves as an SMM with an effective barrier for the magnetization reversal, (Ueff/kB), of 17.1 K. Upon desolvation, Mn2Os exhibits an increase of Ueff/kB to 42.0 K and an opening of the hysteresis loop observable at 1.8 K. Mn2Os·7MeOH shows also exchange-bias behavior with magnetic hysteresis loops exhibiting a shift in the quantum tunneling to 0.25 T from zero-field. The FeIII and RuIII analogues were pre...

Selecting water-alcohol mixed solvent for synthesis of polydopamine nano-spheres using solubility parameter.

Abstract: The solvent plays an important role in a given chemical reaction. Since most reaction in nature occur in the mixed-solvent systems, a comprehensive principle for solvent optimization was required. By calculating the Hansen solubility parameters (HSP) distance Ra, we designed a model experiment to explore the influence of mixed solvents on the chemical synthesis. The synthesis of polydopamine (PDA) in the water-alcohol system was chosen as model. As predicted, the well-dispersed PDA spheres were obtained in selected solvents with smaller Ra values: methanol/water, ethanol/water and 2-propanol/water. In addition, the mixed solvent with smaller Ra values gave a higher conversion of dopamine. The strategy for mixed solvent selection is might be useful to choose optimal reaction media for efficient chemical synthesis.

Empowering a transition-metal-free coupling between alkyne and alkyl iodide with light in water

Abstract: Methods to assemble alkynes are essential for synthesizing fine chemicals, pharmaceuticals and polymeric photo-/electronic materials. Using light as a clean energy form and water as a green solvent has the potential to make synthetic chemistry more environmentally friendly. Here we present a transition-metal-free coupling protocol between aryl alkyne and alkyl iodide enabled by photoenergy in water. Under ultraviolet irradiation and in basic aqueous media, aryl alkynes efficiently couple with a wide range of alkyl iodides including primary, secondary and tertiary ones under mild conditions. A tentative mechanism for the coupling is also proposed.

The effect of solvent choice on the gelation and final hydrogel properties of Fmoc–diphenylalanine

Abstract: Gels can be formed by dissolving Fmoc–diphenylalanine (Fmoc–PhePhe or FmocFF) in an organic solvent and adding water. We show here that the choice and amount of organic solvent allows the rheological properties of the gel to be tuned. The differences in properties arise from the microstructure of the fibre network formed. The organic solvent can then be removed post-gelation, without significant changes in the rheological properties. Gels formed using acetone are meta-stable and crystals of FmocFF suitable for X-ray diffraction can be collected from this gel.

Catalytic chalcogenylation under greener conditions: a solvent-free sulfur- and seleno-functionalization of olefins via I2/DMSO oxidant system.

Abstract: Herein, we report a solvent- and metal-free methodology for the alkoxy-chalcogenylation of styrenes, using molecular iodine as a catalyst, DMSO as a stoichiometric oxidant, and different nucleophiles under microwave irradiation. This eco-friendly approach afforded the desired products in good to excellent yields in only 10 min. In addition, using the same protocol, we carried out the cyclization reaction of relevant molecules, such as lapachol derivatives.

Double-layered reactive microcapsules with excellent thermal and non-polar solvent resistance for self-healing coatings

Abstract: Double-layered polyurea microcapsules containing hexamethylene diisocyanate (HDI) with outstanding shell tightness have been successfully synthesized via interfacial polymerization reaction in an oil-in-water emulsion. The resultant capsules were systematically characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The reaction parameters including reaction temperature (40 °C, 50 °C, 60 °C), reaction duration (1 h, 1.5 h, 2 h and 2.5 h), amount of Suprasec 2644 (2.4 g, 3 g and 3.6 g) and emulsification time (15 min, 45 min and 75 min) were investigated and evaluated in terms of core fraction and quality of microcapsules. The core fraction of microcapsules was reduced with an increase of reaction temperature, reaction duration, mass of Suprasec 2644 and emulsification time, while the quality of microcapsules fluctuated. The thermal and organic solvent resistances were assessed by using TGA and titration. The results showed that the microcapsules had 1.6% weight loss compared with pure HDI with 90% weight loss after 60 min isothermal treatment at 100 °C. After immersion in various solvents for 24 days, the microcapsules released as low as ∼3% of core in weakly polar solvents (i.e. hexane and xylene), about 5–60% in polar aprotic solvents (i.e. ethyl acetate, acetone, DMF and DMSO), and 60–90% in water and polar protic solvents (i.e. isopropanol and ethylene glycol). Both fresh and hexane-treated HDI capsules showed excellent anticorrosion performance in scratched coatings via self-healing functionality, indicating promising practical application in industrial coating and paint systems.

Selective Production of Levulinic Acid from Furfuryl Alcohol in THF Solvent Systems over H-ZSM-5

Abstract: Furfuryl alcohol in high concentrations (1 M) was hydrolyzed to levulinic acid in high yields (>70%) using H-ZSM-5 zeolite as the catalyst in monophasic tetrahydrofuran (THF)–water solvent systems. Reaction kinetics studies using H-ZSM-5 were carried out, and combined with results obtained for other Bronsted acid catalysts, we suggest that the structural properties of H-ZSM-5, in conjunction with increased reaction performance using the polar aprotic solvent THF, are effective for furfuryl alcohol hydrolysis to levulinic acid while inhibiting furfuryl alcohol polymerization reactions. In addition, on the basis of results obtained for a wide range of THF–H2O solvent systems (19:1–1:2 w/w), we suggest that the hydrophobic nature of H-ZSM-5 alters the internal solvent microenvironment within the zeolite framework, allowing for high levulinic acid yields, even at low THF solvent concentrations (e.g., 1:2 THF–H2O w/w).

Deep eutectic solvent based on choline chloride and malonic acid as an efficient and reusable catalytic system for one-pot synthesis of functionalized pyrroles

Abstract: A deep eutectic solvent (DES) based on choline chloride and malonic acid was prepared easily with high purity at a low cost. It has been applied as a dual catalyst and reaction medium for the synthesis of functionalized pyrroles by a one-pot, four-component reaction of amines, aldehydes, 1,3-dicarbonyl compounds and nitromethane. This green solvent could be recycled and reused three times without loss of its efficiency.