Browsing by Author "Nguyen, Van-Huy"

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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.
Temperature effect on the photo-epoxidation of propylene over V-Ti/MCM-41 photocatalyst
(2013-03-05)
Nguyen, Van-Huy
;
Wu, Jeffrey C. S.
;
Bai, Hsunling
;
環境工程研究所
;
Institute of Environmental Engineering
The effect of reaction temperature on the gas-phase photocatalytic epoxidation of propylene was systematically studied over V-Ti/MCM-41 photocatalyst at different temperatures (298-393 K). Temperature significantly influences the product distribution of photo-epoxidation. Raising temperature is favorable towards the formation of propionaldehyde (PA) due to inhibition of PA transformation to propionic acid (C2H5COOH), the intermediate product of acetaldehyde (AA). Results indicated that the reaction temperature has a dual-action to the reaction rate: (1) improving the desorption of reaction products, which provides more active sites for reaction and (2) reducing the adsorption of propylene on the photocatalyst, which declines the reaction efficiency. (C) 2012 Elsevier B.V. All rights reserved.