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Reductive removal of chloroacetic acids by catalytic hydrodechlorination over Pd/ZrO2 catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
45786 46422 2013 9 PDF Available
Title
Reductive removal of chloroacetic acids by catalytic hydrodechlorination over Pd/ZrO2 catalysts
Abstract

Chloroacetic acids are common disinfection byproducts in drinking water and are of significant concern due to their strong carcinogenic, mutagenic and hepatotoxic effects. In the present study, the catalytic hydrodechlorination of chloroacetic acids (monochloroacetic acid, dichloroacetic acid and trichloroacetic acid) was investigated over supported Pd catalysts on SiO2, ZrO2, and activated carbon (AC) prepared by the impregnation method (denoted as im-Pd/support) and/or the deposition-precipitation method (denoted as dp-Pd/support). The catalysts were characterized by X-ray diffraction, transmission electron microscopy, measurement of point of zero charge, N2 adsorption–desorption isotherm, H2 chemisorption, and X-ray photoelectron spectroscopy. Characterization results showed that the points of zero charge of the supports varied. In contrast to im-Pd/ZrO2, strong metal–support interaction was identified in dp-Pd/ZrO2. Accordingly, im-Pd/ZrO2 was found to be more active than im-Pd/AC and im-Pd/SiO2, and dp-Pd/ZrO2 exhibited higher catalytic activity than im-Pd/ZrO2. Complete dechlorination of chloroacetic acids to acetic acid could be achieved on dp-Pd/ZrO2 within 120 min of hydrodechlorination. The hydrodechlorination rate constants of trichloroacetic acid, dichloroacetic acid, and monochloroacetic acid over dp-Pd(1.74)/ZrO2 were 0.22, 0.16, and 0.044 min−1, respectively, reflecting an increase in dechlorination activity with increasing number of chlorine atoms in chloroacetic acids. It was further demonstrated that the catalytic hydrodechlorination was accomplished via a combined stepwise and concerted pathway for both trichloroacetic acid and dichloroacetic acid.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Chloroacetic acids were readily dechlorinated to acetic acid by the liquid phase catalytic hydrodechlorination over Pd/ZrO2 catalysts. ► Pd/ZrO2 catalyst prepared by the deposition precipitation method exhibited higher catalytic activity than that by the impregnation method. ► Dichloroacetic acid and trichloroacetic acid were dechlorinated via a combined stepwise and concerted pathway.

Keywords
Chloroacetic acids; Catalytic hydrodechlorination; Supported Pd catalyst; Metal–support interaction
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Reductive removal of chloroacetic acids by catalytic hydrodechlorination over Pd/ZrO2 catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volumes 134–135, 2 May 2013, Pages 222–230
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us