Technical Center Asia Ltd

Rayong, Thailand

Technical Center Asia Ltd

Rayong, Thailand
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Kaweetirawatt T.,Ube Technical Center Asia Co. | Kaweetirawatt T.,Yamaguchi University | Yamaguchi T.,Yamaguchi University | Hayashiyama S.,Yamaguchi University | And 3 more authors.
RSC Advances | Year: 2012

Nylon 6 depolymerization in supercritical (SC) alcohols was theoretically studied using the QM/MC/FEP method. All geometry optimizations and the Gibbs free energy calculation in the gas phase were calculated at the B3LYP/6-31++G(d,p) level of theory. The effect of different types of alcohols, methanol (MeOH) and isopropanol (iPrOH), is the focus on this investigation. There are two candidates for the depolymerization mechanism. One is an intermolecular mechanism (Rxn A), which produces aminocaproic ester as the major product. The other is an intramolecular mechanism (Rxn B), directly giving ε-caprolactam. The activation free energies (ΔG ‡ rxn) of Rxn A in the two alcohols are lower by 8-9 kcal mol -1 than those of Rxn B. Thus, the calculated rate constants (k) of Rxn A are much larger than those of Rxn B. The cyclization route to the aminocaproic ester is preferable by more than 15.0 kcal mol -1 to the alkylation at the amino group, and aminocaproic ester exclusively produces ε-caprolactam. The further reaction of ε-caprolactam, such as N-alkylation, is able to proceed only in MeOH. The activation free energies of the cyclization of aminocaproic acid are almost the same as those of the aminocaproic ester in the SC alcohols. This journal is © 2012 The Royal Society of Chemistry.

Teeka J.,Yamaguchi University | Imai T.,Yamaguchi University | Reungsang A.,Khon Kaen University | Cheng X.,Yamaguchi University | And 8 more authors.
Journal of Industrial Microbiology and Biotechnology | Year: 2012

Biodiesel-contaminated wastewater was used to screen for PHAs-producing bacteria by using crude glycerol as the sole carbon source. A gram-negative THA-AIK7 isolate was chosen as a potential PHAs producer. The 16S rRNA phylogeny indicated that THA-AIK7 isolate is a member of Novosphingobium genus which is supported by a bootstrap percentage of 100% with Novosphingobium capsulatum. The 1,487 bp of 16S rRNA gene sequence of THA-AIK7 isolate has been deposited in the GenBank database under the accession number HM031593. Polymer content of 45% cell dry weight was achieved in 72 h with maximum product yield coefficient of 0.29 g PHAs g -1 glycerol. Transmission electron micrograph results exhibited the PHAs granules accumulated inside the bacterial cell. PHAs polymer production in mineral salt media supplemented with 2% (w/v) of crude glycerol at initial pH 7 was extracted by the sodium hypochlorite method. Polymer film spectrographs from Nuclear magnetic resonance displayed a pattern of signal virtually identical to spectra of commercial PHB. Thermal analysis by Differential scanning calorimeter showed a melting temperature at 179C°. Molecular weight analysis by Gel permeation chromatography showed two main peaks of 133,000 and 700 g mol-1 with weight-average molecular weight value of 23,800 and number-average molecular weight value of 755. Endotoxinfree of PHAs polymer was preliminarily assessed by a negative result of the gel-clot formation, Pyrotell Single test vial, at sensitivity of 0.25 EU ml -1. To our knowledge, this is the first reported test of endotoxin-free PHAs naturally produced from gram-negative bacteria which could be used for biomedical application. © Society for Industrial Microbiology and Biotechnology 2012.

Vongachariya A.,Chulalongkorn University | Vongachariya A.,Technical Center Asia Ltd | Iamsamai C.,Chulalongkorn University | Saengsawang O.,Chulalongkorn University | And 4 more authors.
Journal of Computational and Theoretical Nanoscience | Year: 2012

The effect of the surface curvature of the single-wall carbon nanotube (SWCNT) on the cationic-π interaction was investigated for four different monovalent cations (Li+, Na+, K+ and NH+ 4, complexed both inside and outside of the (m n)-armchair SWCNTs where m = n = 6-10. Calculations were carried out using the density functional methods at the PBE/DNP level. For both types of complexes and for all four cations, increasing the tube's curvature (decreasing the diameter) leads to a decrease in the binding energy (Ebind), binding distance and cationic net charge. In addition, the cations can bind better to the outer than the inner surfaces in which the absolute values of the energy difference between the two types of complex (Ebind) is narrower for the larger diameter than the smaller SWCNTs. The curvature effect is expected to vanish when (Ebind) = 0, which was derived from extrapolation to be at SWCNT diameters of 19.74 A, 21.23 A, 22.15 A and 24.09 A for the Li+, Na+, K+ and NH+ 4 cations, respectively. Copyright © 2012 American Scientific Publishers. All rights reserved.

Rattanatraicharoen P.,Yamaguchi University | Rattanatraicharoen P.,Technical Center Asia Ltd | Tanaka Y.,Yamaguchi University | Shintaku K.,Yamaguchi University | And 4 more authors.
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2013

Optically active poly(m-phenylene)s substituted with chiral oxazoline derivatives have been synthesized by the nickel-catalyzed Yamamoto coupling reaction of optically active (S)-4-benzyl-2-(3,5-dihalidephenyl)oxazoline derivatives (X = Br or I). The structures and chiroptical properties of the polymers were characterized by spectroscopic methods and thermal gravimetric analyses. The polymers showed higher absolute optical specific rotation values than their corresponding monomer, and showed a Cotton effect at transition region of conjugated main chain. The optical activities of the polymers should be attributed to the higher order structure such as helical conformations. Moreover, the helical conformation could be induced by addition of metal salts into polymer solutions. The polymers showed good thermal stabilities, which was attributable to the oxazoline side chains. © 2012 Wiley Periodicals, Inc.

Rungrotmongkol T.,Chulalongkorn University | Arsawang U.,Chulalongkorn University | Iamsamai C.,Chulalongkorn University | Vongachariya A.,Technical Center Asia Ltd | And 4 more authors.
Chemical Physics Letters | Year: 2011

In order to explain the solubility of carbon nanotubes (CNT), including single walled CNTs, wrapped with chitosan of a 60% degree of deacetylation, MD simulations were applied to represent three chitosan concentrations, using two pristine CNTs (pCNT-pCNT), and one and two CNTs wrapped (pCNT-cwCNT and cwCNT-cwCNT). The CNT aggregation was observed in pCNT-pCNT and pCNT-cwCNT due to van der Waals interactions between tube-tube aromatic rings, and inter-CNT bridging by chitosan, respectively. At higher chitosan concentrations, such that most to all of CNTs were wrapped with chitosan, charge-charge repulsion was found to separate robustly the cwCNTs and lead to a well dispersed solution. © 2011 Elsevier B.V. All rights reserved.

Kaweetirawatt T.,Ube Technical Center Asia Co. | Kaweetirawatt T.,Yamaguchi University | Kokita Y.,Yamaguchi University | Iwai S.,Yamaguchi University | And 2 more authors.
Chemical Physics Letters | Year: 2012

The hydrolysis of ethyl benzoate in acidic condition was theoretically studied for models with two (2W) or three water (3WA) molecules at the B3LYP/6-311++G(d,p) levels of theory. Activation free energy of solvation in aqueous solution (ΔG ‡ cal) was calculated using the QM/MC/FEP method. The value of the 2W model in aqueous solution was calculated to be smaller by more than 5.0 kcal mol -1 than the observed value (26.0 kcal mol -1 at 298 K). The position of the third water molecule in the 3WA model plays an essential role in producing the ΔG ‡ cal value (26.4 kcal mol -1) consistent with the experimental value. © 2012 Elsevier B.V. All rights reserved.

Kaweetirawatt T.,Ube Technical Center Asia Co. | Kaweetirawatt T.,Yamaguchi University | Yamaguchi T.,Yamaguchi University | Higashiyama T.,Nissan Chemical Industries Ltd Chiba | And 2 more authors.
Journal of Physical Organic Chemistry | Year: 2012

In this study, the tautomeric equilibrium between the keto and enol forms has been studied for five typical ketones and aldehydes: i-butanal, acetaldehyde, acetone, acetylacetone, and dimedone. The level of theory used in the gas-phase calculation was Becke, three-parameter, Lee-Yang-Parr/6-311G(d,p)/ /Becke, three-parameter, Lee-Yang-Parr/6-31G(d). The free energies of solvation were included in the calculation by using the free-energy perturbation method based on Monte Carlo simulation, that is, the quantum mechanical/Monte Carlo/free-energy perturbation method. Three different models, incorporating no-water, one-water, and two-waters, were adopted. The results showed that in the gas phase the addition of water molecules to the reaction mechanism caused the activation barriers (ΔG‡ gas) to decrease by half relative to the water-free mechanism, but there was no effect on the relative difference in free energy, ΔGgas. The solvation effects (ΔGsol), based on quantum mechanical/Monte Carlo/free-energy perturbation calculations, were added to those of the gas-phase results of the one-water and two-waters models. The two-waters model produced values that were very consistent with the experimental data for all of the tautomers. The differences in the relative Gibbs free energy (ΔG rxn) were less than 1.0 kcal mol-1. In summary, the inclusion of solvent molecules in gas-phase calculations plays a very important role in producing results consistent with experimental data. Copyright © 2012 John Wiley & Sons, Ltd.

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