From Diols to Lactones under Aerobic Conditions using a Laccase/TEMPO Catalytic System in Aqueous Medium

An efficient catalytic system to oxidize quantitatively aliphatic diols using Trametes versicolor laccase and TEMPO has been developed in aqueous medium. Oxidations have occurred in a non‐stereoselective fashion but with complete regio‐ and/or monoselectivity, obtaining lactones with excellent purity after simple extraction. This catalytic system has been demonstrated to be scalable, compatible with the presence of a variety of functionalities, and also allowed the successful enzyme recycling using a laccase‐cross‐linked enzyme aggregates (CLEA) preparation.     

Theoretical study on the relationship between the molecular structure and corrosion inhibition efficiency of long alkyl side chain acetamide and isoxazolidine derivatives

Quantum mechanics calculations have been applied to three long alkyl side chain acetamides and three isoxazolidine derivatives used as corrosion inhibitors. The corresponding structures have been optimized, and the highest occupied molecular orbital energy (E _HOMO), the lowest unoccupied molecular orbital energy (E _LUMO), energy gap (??E), electronegativity (??), hardness (??), softness (??) and the fraction of electrons transferred from the inhibitor molecule to the metal surface (??N) have been calculated using the DFT/B3LYP and HF methods with the 6?C31G(d, p) basis set. The electric dipole moment (??), the mean polarizability (??????) and the first order hyperpolarizability (??) values of the investigated molecules have been computed using the same methods. The calculation results also show that the molecules might have microscopic nonlinear optical (NLO) behaviour with non-zero values. Finally, the theoretical results obtained have been compared with the experimental data.     

Reconstruction of nonuniformly sampled time-limited signals using prolate spheroidal wave functions

Shannon's sampling theory is based on the reconstruction of bandlimited signals which requires infinite number of uniform time samples. Indeed, one can only have finite number of samples for numerical implementation. In this paper, as a dual of the bandlimited reconstruction, a solution for time-limited signal reconstruction from nonuniform samples is proposed. The system model we present is based on the idea that time-limited signals which are also nearly bandlimited can be well approximated by a low-dimensional subspace. This can be done by using prolate spheroidal wave functions as the basis. The order of the projection on this basis is obtained by means of the time–frequency dimension of the signal, especially in the case of non-stationary signals. The reconstruction requires the estimation of the nonuniform sampling times by means of an annihilating filter. We obtain the reconstruction parameters by solving a linear system of equations and show that our finite-dimensional model is not ill-conditioned. The practical aspects of our method including the dimensionality reduction are demonstrated by processing synthetic as well as real signals.     

Production of a Solvent Yellow 124 “euromarker” reference material certified for purity

Solvent Yellow 124 (SY124, N-ethyl-N-[2(isobutoxyethoxy)ethyl]-4-(phenylazo)aniline) is used as a common low tax fuel marker in European Union member countries. It is added to these fuels which may also contain traditional dyes, to prevent misuse. SY124 is produced industrially in solution (typically aromatic hydrocarbons) and its purity can vary from batch to batch. This is particularly a problem for the petroleum industry which risks large fines if SY124 levels are found to be below 6 mg/L or above 9 mg/L. A new reference material for SY124, certified for purity was prepared to address this problem.A SY124 CRM was prepared from a commercially procured solution of SY124. The details of the preparation and certification will be discussed. The material is commercially available as ERM-AC316a, packaged as 200 mg units in screw cap 4 mL amber glass vials. Its purity value is 95.0 ± 1.2% m/m at the 95% confidence interval.     

Optimization of enzymatic methanolysis of soybean oil by response surface methodology

Enzymatic methanolysis of refined soybean oil with methanol was investigated using Rhizomucor miehei lipase, Lipozyme RM IM, in n-hexane for reaction times of 30 min. Response surface methodology (RSM) based on three-level, three-factor (variable) face-centered cube design was used for the optimization of methanolysis. The independent variables that affect the methanolysis reaction conducted in n-hexane are temperature (°C), enzyme/oil weight ratio, and oil/methanol molar ratio. A good quadratic model was obtained for the methyl ester production by multiple regression and backward elimination. A linear relationship was observed between the observed and predicted values (R²−0.9635). The effects of temperature and enzyme amount, which affected methyl ester content of the product (response) positively, were significant (P<0.01). The quadratic term of temperature and the interaction term of enzyme amount with temperature affected the response negatively (P<0.01). The interaction term of enzyme amount with substrate mole ratio had a positive effect on the response (P<0.05). Critical conditions for the response at which methyl ester content of the product was 76.9% were determined to be 50°C, 2.37 methanol/oil mole ratio, and 0.09 enzyme/oil weight ratio.     

Thermodynamic analysis of steam assisted conversions of bio-oil components to synthesis gas

The aim of this study is to investigate the thermodynamics of steam assisted, high-pressure conversions of model components of bio-oil – isopropyl alcohol, lactic acid and phenol – to synthesis gas (H₂ + CO) and to understand the effects of process variables such as temperature and inlet steam-to-fuel ratio on the product distribution. For this purpose, thermodynamic analyses are performed at a pressure of 30 bar and at ranges of temperature and steam-to-fuel ratio of 600–1200 K and 4–9, respectively. The number of moles of each component in the product stream and the product composition at equilibrium are calculated via Gibbs free energy minimization technique. The resulting optimization problems are solved by using the Sequential quadratic programming method. The results showed that all of the model fuels reached near-complete conversions to H₂, CO, CO₂ and CH₄ within the range of operating conditions. Temperature and steam-to-fuel ratio had positive effects in increasing hydrogen content of the product mixture at different magnitudes. Production of CO increased with temperature, but decreased at high steam-to-fuel ratios. Conversion of model fuels in excess of 1000 K favored molar H₂/CO ratios around 2, the synthesis gas composition required for Fischer–Tropsch and methanol syntheses. It was also possible to adjust the H₂/CO ratios and the amounts of CH₄ and CO₂ in synthesis gas by steam-to-fuel ratio, the value depending on temperature and the fuel type. Product distribution trends indicated the presence of water–gas shift and methanation equilibria as major side reactions running in parallel with the steam reforming of the model hydrocarbons.     

Silica embedded cobalt(0) nanoclusters: Efficient, stable and cost effective catalyst for hydrogen generation from the hydrolysis of ammonia borane

Cobalt(0) nanoclusters embedded in silica (Co@SiO₂) were prepared by a facile two-step procedure. In the first step, the hydrogenphosphate anion (HPO₄²⁻) stabilized cobalt(0) nanoclusters were in situ generated from the reduction of cobalt(II) chloride during the hydrolysis of sodium borohydride (NaBH₄) in the presence of stabilizer. Next, HPO₄²⁻ anion-stabilized cobalt(0) nanoclusters were embedded in silica formed by in situ hydrolysis and condensation of tetraethylorthosilicate added as ethanol solution. Co@SiO₂ can be separated from the solution by vacuum filtration and characterized by UV-Vis electronic absorption spectroscopy, TEM, SEM-EDX, ATR-IR and ICP-OES techniques. Co@SiO₂ are found to be highly active and stable catalysts in the hydrolysis of ammonia borane (AB) even at low cobalt concentration and room temperature. They provide an initial turnover frequency of 13.3 min⁻¹ and 24,400 total turnovers over 52 h in the hydrolysis of AB at 25.0 ± 0.5 °C. Moreover, Co@SiO₂ retain 72% and 74% of the initial activity after ten runs recyclability and five cycles reusability test in the hydrolysis of AB, respectively. The kinetics of hydrogen generation from the hydrolysis of AB catalyzed by Co@SiO₂ was studied depending on the catalyst concentration, substrate concentration, and temperature. The activation parameters of this catalytic reaction were also determined from the evaluation of the kinetic data.     

Dielectric,thermal, and swelling properties of calcium ion‐crosslinked sodium alginate film

In this study, Ca²⁺‐crosslinked sodium alginate (SA) gel films (SA‐Ca/SA2‐Ca) have been prepared, and their structural and thermal characterizations were investigated using fourier transform infrared spectroscopy, X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis, respectively. Dielectric characterization was performed at room temperature in the frequency range of 12 Hz–100 kHz. The equilibrium swelling value (ESV) of gel films was determined both in distilled water and in 0.1 M sodium chloride (NaCl) solution at room temperature. Sodium alginate films (SA/SA2) were also prepared for use as reference. The effect of the crosslinking of sodium alginate on the dielectric and thermal properties of gel films was investigated by comparing the properties of gel films with those of SA/SA2 films. Although ESV of Ca²⁺‐crosslinked SA film in distilled water is about 350 /g_polymer, it decreased into one third in 0.1 M NaCl solution. The crosslinking of SA did not significantly affect the thermal properties, but it decreased the β‐relaxation associated with the polar side groups. Frequency spectra of electric modulus, impedance and Cole‐Cole plots confirmed the higher conductance values of SA‐Ca films at low frequencies than those of SA film due to the presence of by‐product of crosslinking. POLYM. ENG. SCI., 54:1372–1382, 2014. © 2013 Society of Plastics Engineers     

In vitro characterization of chitosan scaffolds: influence of composition and deacetylation degree

In this study, the influence of degree of deacetylation (DD) and composition on some structural and biological properties of chitosan scaffolds were examined in vitro. 3D chitosan scaffolds of 2% (w/v) and 3% (w/v) composition in different DDs i.e. 75–85% and >85% were prepared by freeze-drying method at −80 °C. We noticed that >85% deacetylated chitosan scaffolds of 2% (w/v) composition has a highly interconnected morphological structure having ∼100 μm pore size with 0.0917 N/mm² compression modulus. L929 fibroblastic cells were cultured on chitosan scaffolds in order to evaluate their biocompatibilities. Cell culture studies demonstrated that fibroblastic cell attachment and proliferation is affected by DD. The higher deacetylated chitosan scaffolds strongly supported the attachment and proliferation when compared with the lower deacetylated scaffolds. MTT assay indicated that >85% deacetylated chitosan scaffolds of 2% (w/v) composition, having the highest specific growth rate 0.017 h⁻¹ of all, was found to be the most suitable for cell culture studies and a potential candidate for tissue engineering with enhanced biostability and good biocompatibility.     

Parametric characterizations in superparamagnetic latex

The effect of synthesis parameters on the production of superparamagnetic latex, which are magnetite nanoparticles covered with a poly(methyl methacrylate) layer, were studied. The synthesis method was based on the developed route of emulsifier-free emulsion polymerization. Under this study, effects of the monomer and initiator concentrations, the amount of magnetic sol, the stirring rate and the adding rate of the magnetic sol on the properties of synthesized latexes were investigated. The characterizations were performed by a high resolution transmission electron microscopy, a dynamic light scattering, a vibrating sample magnetometer and a gel permeation chromatography. The results showed that the monomer concentration was found to be the most effective parameter on latex stability. As the initiator amount and the stirring rate increased, saturation magnetization and average molecular weight decreased due to the reactions occurring between surfaces of magnetite nanoparticles and initiator fragments. On increasing amount of magnetic sol, the saturation magnetization and polymer molecular weight increased but the size of nanospheres was unchanged because of the ions in magnetic sol. It was seen that the desired size and magnetic properties of the latex could be obtained since the parameters were found to have substantial impact on their properties.