(617gp) Aqueous-Phase Hydrodechlorination of Trichloroethene over Pd-Supported on Swellable Organically-Modified Silica (SOMS)
AIChE Annual Meeting
Wednesday, November 16, 2016 - 6:00pm to 8:00pm
Gokhan Celik1, Hyuntae Sohn1, Seval Gunduz1, Saurabh A. Ailawar1, Paul Edmiston2, Umit. S. Ozkan1*
1The Ohio State University, Columbus, Ohio 43210 (United States)
2The College of Wooster, Wooster, Ohio, 44691 (United States)
The widespread contamination of water by chlorinated ethenes such as trichloroethene (TCE) and perchloroethene (PCE) is a growing environmental concern . The high level of toxicity and the carcinogenic effects of TCE pose a serious threat to human health and the environment. According to a study conducted by Environmental Protection Agency, TCE was detected in 91 out of 945 drinking-water and groundwater samples . Hydrodechlorination (HDC) is an efficient way of removing chlorinated compounds from water. It is an elimination-based remediation technique in which chlorinated compounds react with hydrogen and are catalytically converted to Cl-free hydrocarbons and hydrogen chloride. There has been on-going research on HDC of chlorinated compounds where promising catalytic activities have been obtained with the palladium-based state-of-the-art catalysts. However, catalyst deactivation due to anionic groundwater constituents such as sulfur species, nitrates, carbonates, and chlorides is a recurring problem [3, 4]. For industrial organizations to adapt catalytic HDC as their remediation technique, deactivation issues due to the anionic species need to be addressed.
Herein, we report the use of a new class of materials, namely swellable organically-modified silica (SOMS) as a catalyst support for HDC reactions. SOMS is extremely hydrophobic and has a high affinity for absorbing organics. While absorption of organics is in progress, SOMS swells in such a way that its volume physically expands to more than 3-6 times of its original size [5-7]. Active metals incorporated within the SOMS matrix in its expanded state are protected from dissolved anions present in water. Hydrophobic nature of these materials will also create a repulsive force against water and its constituents. This will result in an additional level of protection of active sites. SOMS can have the potential to address the deactivation issues involved in catalytic HDC.
In this study, Pd-incorporated SOMS (Pd/SOMS) and Pd/Al2O3, for comparison purposes, have been tested for HDC of TCE. Reaction experiments and characterization studies including N2 physisorption, solid-state NMR, laser RAMAN and infrared spectroscopy, extended X-ray absorption fine structure (EXAFS), and inductively coupled plasma optical emission spectrometer (ICP-OES) have been performed to understand the poison-resistant characteristics of Pd/SOMS.
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