Browsing by Author "Lin, Shawn D."

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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
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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.
Influence of co-feeds additive on the photo-epoxidation of propylene over V-Ti/MCM-41 photocatalyst
(2015-05-01)
Nguyen, Van-Huy
;
Lin, Shawn D.
;
Wu, Jeffrey C. S.
;
Bai, Hsunling
;
環境工程研究所
In this work, the effects of co-feed species, namely, H2O or H-2, on the photocatalytic epoxidation of propylene over V-Ti/MCM-41 are examined. A promoting effect on the C3H6 consumption rate is found under 0.6 kPa H2O co-feed when the PO (propylene oxide) formation rate is not proportionally promoted, resulting a slightly decreased PO selectivity. With increasing H2O concentration, the reaction activity decreases and this can be attributed to surface site blocking by excess H2O. The presence of H2O also increases the stability of photocatalyst during reaction. Similar observation of the enhanced C3H6 consumption rate and the improved stability is found when 5.6 kPa H-2 is used as co-feed. We found that the catalyst stability is improved when the AA (acetaldehyde) is increased. This suggests that AA accumulation on the catalyst surface may lead to surface fouling and the observed deactivation. The presence of H2O or H-2 co-feed, which can lead to hydroxyl radical (OH.), may impose a shift in the production formation of photocatalytic reaction. (C) 2014 Elsevier B.V. All rights reserved.