High activity and regenerability of a palladium-gold catalyst for chloroform degradation

• Published in: Journal of chemical technology and biotechnology (1986) Vol. 91; no. 10; pp. 2590 - 2596
• Main Authors: Velázquez, Juan C, Leekumjorn, Sukit, Hopkins, Gary D, Heck, Kimberly N, McPherson, Jason S, Wilkens, John A, Nave, Bradley S, Reinhard, Martin, Wong, Michael S
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.10.2016; Wiley Subscription Services, Inc
• Subjects: Buffers; Catalysis; Catalysts; dechlorination; Degradation; Deionization; environmental remediation; Groundwater; heterogeneous catalysis; Palladium; reactor optimization; Reactors; volatile organic compounds (VOCs)
• ISSN: 0268-2575; 1097-4660
• DOI: 10.1002/jctb.4851

BACKGROUND Chloroform (CF), a common groundwater contaminant, can be degraded in deionized water reductively using Pd and Pd‐Au catalysts under mild conditions (room temperature, atmospheric pressure) via hydrodechlorination (HDC). However, the performance of these catalysts under field‐like conditions is unknown. This study evaluates the lab‐scale performance and optimal operating conditions for flow reactors using Pd/Al2O3 and Pd‐Au/Al2O3. RESULTS Both catalysts were active for CF HDC when tested using deionized water and groundwater spiked with CF. The Pd‐Au catalyst was ∼263× more active than the Pd catalyst using unbuffered deionized water (1550 mL‐gPd−1‐min−1 vs 5.89 mL‐gPd−1‐min−1), and was ∼137× more active using buffered groundwater (1030 mL‐gPd−1‐min−1 vs 7.53 mL‐gPd−1‐min−1). The buffer was a carbonate/citrate mixture optimized to prevent pH drop and scale formation from minerals present in groundwater. A catalytic flow process was designed using a buffer co‐feed and daily regeneration of the catalyst bed. Pd‐Au/Al2O3‐ and Pd/Al2O3‐containing reactors exhibited CF conversions of 65% and 32.5% over 18 days operating at a weight hourly space velocity of 30 h−1. CONCLUSIONS This study provides insights into strategies for long‐term operation of catalytic flow reactors to treat CF in groundwater, and shows the higher CF HDC catalytic efficiency of Pd‐Au over Pd. © 2015 Society of Chemical Industry