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Vu T.H.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Au H.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Nguyen T.M.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Pham M.T.,National Key Laboratory for Petrochemical and Refinery Technologies | And 2 more authors.
Catalysis Science and Technology | Year: 2013

The efficacy of a potassium 12-phosphotungstate (KPW) catalyst in the synthesis of methyl 2-keto-l-gulonat from 2-keto-l-gulonic acid (2-KLGA) and methanol is investigated. The KPW catalyst gives high yields in short reaction times. The present procedure represents a clean, efficient, practical, simple, mild, time-saving and eco-friendly method for the synthesis of methyl 2-keto-l-gulonat. The KPW catalyst is found to be a truly heterogeneous catalyst, highly efficient and reusable in the synthesis of methyl 2-keto-l-gulonat. © 2013 The Royal Society of Chemistry. Source


Vu T.H.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Au H.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Nguyen T.H.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Nguyen T.T.T.,National Key Laboratory for Petrochemical and Refinery Technologies | And 3 more authors.
Catalysis Letters | Year: 2013

A biosolvent composition containing ethyl lactate and biodiesel was directly obtained by catalytic extractive esterification of lactic acid. Since the esterification of organic acids with alcohols is a thermodynamically limited reaction, the methodology consists in conducting the esterification and the ester extraction simultaneously thereby shifting the equilibrium towards more esters. The acid catalyzed esterification was performed in a biphasic solvent system composed of (i) a reactive polar phase which contains the esterification constituents, lactic acid, ethanol and an acid catalyst (ii) an extractive solvent selective of the ester, fatty acid methyl ester (biodiesel). This solvents system increases the ethyl lactate yield of more than 30 %. During the reaction progress, the selective solvent, fatty acid methyl ester, is progressively blended with ethyl lactate providing a mixture of esters, which can be directly used as an efficient composition of biosolvents without further purification. The solid acidic potassium salt of 12-phosphotungstic acid, K 2.5H0.5PW12O40, was shown to be more efficient than the conventional esterification catalysts, H2SO 4 or Amberlyst 15. K2.5H0.5PW 12O40 gives a yield in ethyl lactate higher than 80 mol% after 2 h of reaction in the biphasic solvent system, using a molar ratio ethanol/lactic acid of 3.3 only. Moreover, K2.5H0.5PW 12O40 shows a remarkable higher activity per protonic sites (factor 30) and is recyclable at least two times without apparent loss of activity. These excellent properties were ascribed to its low density of strong Brønsted acid sites and its adequate hydrophobicity which would make this acid more water tolerant than the conventional esterification catalysts, H 2SO4 or Amberlyst 15. Graphical Abstract: Acid catalyzed esterification of lactic acid with ethanol was performed in a biphasic system where biodiesel acts as an extractive solvent of ethyl lactate. This extractive reaction produces directly a composition of biosolvent: biodiesel blended with ethyl lactate.[Figure not available: see fulltext.] © 2013 Springer Science+Business Media New York. Source


Vu T.H.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Au H.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Tran L.T.,National Key Laboratory for Petrochemical and Refinery Technologies | Nguyen T.M.T.,National Key Laboratory for Petrochemical and Refinery Technologies | And 4 more authors.
Journal of Materials Science | Year: 2014

Titanium dioxide (TiO2) nanotubes were synthesized via one-step dynamic hydrothermal process from commercial TiO2 powder. The effects of NaOH concentration, reaction time, reaction temperature, stirring process and washing on the morphology, and the exchange ions of the nanotubes were investigated. The morphology of the nanotubes was characterized in detail with transmission electron microscopy and scanning electron microscope. In the dynamic hydrothermal process, stirring can reduce the reaction time of transformation from particles to nanotubes. The nanotubes were formed when the expected reaction temperature reached to 130 °C. Energy dispersive X-ray analysis was used to determine the exchange of sodium ions and protons in washing process. The Na+ ions attached in the nanotubes were removed completely by HCl aqueous solution and deionized water treatments. X-ray diffraction patterns showed the titanate phase of the as-synthesized sample and anatase phase of TiO2 nanotubes after calcination process at 400 °C for 2 h. © 2014 Springer Science+Business Media New York. Source

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