Browsing by Author "Van-Huy Nguyen"

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Artificial sunlight and ultraviolet light induced photo-epoxidation of propylene over V-Ti/MCM-41 photocatalyst
(2014-05-05)
Van-Huy Nguyen
;
Lin, Shawn D.
;
Wu, Jeffrey Chi-Sheng
;
Bai, Hsunling
;
環境工程研究所
The light irradiation parameters, including the wavelength spectrum and intensity of light source, can significantly influence a photocatalytic reaction. This study examines the propylene photo-epoxidation over V-Ti/MCM-41 photocatalyst by using artificial sunlight (Xe lamp with/without an Air Mass 1.5 Global Filter at 1.6/18.5 mW.cm(-2)) and ultraviolet light (Mercury Arc lamp with different filters in the range of 0.1-0.8 mW.cm(-2)). This is the first report of using artificial sunlight to drive the photo-epoxidation of propylene. Over V-Ti/MCM-41 photocatalyst, the propylene oxide (PO) formation rate is 193.0 and 112.1 mu mol.gcat(-1).h(-1) with a PO selectivity of 35.0 and 53.7% under UV light and artificial sunlight, respectively. A normalized light utilization (NLU) index is defined and found to correlate well with the rate of both PO formation and C3H6 consumption in log-log scale. The light utilization with a mercury arc lamp is better than with a xenon lamp. The selectivity to PO remains practically unchanged with respect to NLU, suggesting that the photo-epoxidation occurs through the same mechanism under the conditions tested in this study.
Direct gas-phase photocatalytic epoxidation of propylene with molecular oxygen by photocatalysts
(2012-01-01)
Van-Huy Nguyen
;
Chan, Hsiang-Yu
;
Wu, Jeffrey C. S.
;
Bai, Hsunling
;
環境工程研究所
The photocatalytic epoxidation of propylene by molecular oxygen is one of the best methods to produce propylene oxide (PO) from the environmental viewpoints. The key is using photo-energy to achieve high PO selectivity and yield at mild conditions. A series of photocatalysts including SiO2, TiO2, V-Ti/MCM-41, V2O5/SiO2, Au/TiO2 and TS-1, were used to evaluate their performance in the photo-epoxidation. The photocatalytic epoxidation of propylene was carried out in the gas mixture of C3H6:O-2:N-2 = 1:1:18 at atmospheric pressure. In addition to PO, other products, such as propionaldehyde, acetone, acetaldehyde, ethanol and methanol, were detected. The results indicated that the most favorable photocatalysts for photocatalytic epoxidation were silicates supported group. The highest PO formation rate of 114 mu mol g cat(-1) h(-1) with selectivity of 47% was obtained over V-Ti/MCM-41 on stream after 4 h at 50 degrees C and atmospheric pressure under UVA irradiation of 0.2 mW/cm(2). In addition, the selectivity of products was very stable on stream. A possible reaction mechanism was proposed based on the knowledge of species presented during the photocatalytic reaction. (C) 2011 Elsevier B.V. All rights reserved.
Real-Time Raman Monitoring during Photocatalytic Epoxidation of Cyclohexene over V-Ti/MCM-41 Catalysts
(2015-06-01)
Chan, Hsiang-Yu
;
Van-Huy Nguyen
;
Wu, Jeffrey C. S.
;
Calvino-Casilda, Vanesa
;
Banares, Miguel A.
A series of V- and/or Ti-loading MCM-41 catalysts are successfully synthesized with a hydrothermal method. The photocatalytic and thermal epoxidations of cyclohexene in the presence of tert-butyl hydroperoxide (t-BuOOH) were investigated with real-time monitored by NIR-Raman spectroscopy. It suggests that both V- and Ti-loading can be responsible for the cyclohexene epoxidation. Moreover, the complementary behavior of V- and Ti-loading may be related to a similar role of activation. Interestingly, the progress of the photo-epoxidation on V0.25Ti2/MCM-41 photocatalyst was monitored by changes in intensity of the characteristic Raman bands without interference from the UV-light irradiation. The result, for the first time, reveals that cyclohexene was directly photo-epoxidized to 1,2-epoxycyclohexane by t-BuOOH during the reaction. A possible mechanism of cyclohexene photo-epoxidation is also proposed for this study.