(762a) Aqueous Phase Hydrodechlorination of Trichloroethylene Using Pd Supported on Swellable Organically Modified Silica (SOMS): Deactivation Due to Chloride and Sulfur Species
The main focus of this study lies in the implementation of SOMS as a catalyst support for HDC of TCE. SOMS belongs to the class of bridged polysilsesquioxanes, which are hybrid organic-inorganic materials, synthesized by sol-gel technique. Post gel formation, the surface of SOMS is made hydrophobic by derivatizing the silanol groups with hexamethyldisilazane. SOMS swells to almost 3 times itâs dry volume, in presence of organic solvents. Apart from this, properties such as, mesoporosity, high surface area and high absorption capacity towards organics, also make SOMS a strong candidate for a catalyst support. This study aims at investigating the effects of chloride and sulfur species on the performance of Pd supported on SOMS for HDC of TCE.
Chloride and sulfur treated catalysts were characterized by extended X-ray absorption fine structure (EXAFS), inductively coupled plasma optical emission spectrometry (ICP-OES), transmission electron microcopy (TEM) in order to investigate the resistance exhibited by SOMS matrix towards these species[5, 6]. Additionally, phenomena such as reduction of Pd by H2 dissolved in aqueous phase under ambient conditions and swelling of SOMS by solvents such as ethanol, were investigated by in-situ X-ray absorption near edge structure (XANES) and near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) respectively. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and laser Raman spectroscopy were also used to explore different characteristics of Pd/SOMS and their role in HDC of TCE. Commercially obtained Pd/Al2O3 was used as the basis of comparison for performance and deactivation resistance of Pd/SOMS. The results elucidate the effects of different chloride and sulfur species, eg. perchlorates, sulfides and sulfates, with varied pH environments on the activity of Pd/SOMS and the role of SOMS in preventing deactivation. Finally, they show that SOMS has great potential to serve as a catalyst support for HDC of TCE.
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 G. Celik, S.A. Ailawar, S. Gunduz, J.T. Miller, P.L. Edmiston, U.S. Ozkan, Aqueous-phase hydrodechlorination of trichloroethylene over Pd-based swellable organically-modified silica (SOMS): Catalyst deactivation due to chloride anions, Applied Catalysis B: Environmental, 239 (2018) 654-664.
 G. Celik, S.A. Ailawar, S. Gunduz, J.T. Miller, P.L. Edmiston, U.S. Ozkan, Aqueous-Phase Hydrodechlorination of Trichloroethylene over Pd-Based Swellable Organically Modified Silica: Catalyst Deactivation Due to Sulfur Species, Industrial & Engineering Chemistry Research, 58 (2019) 4054-4064.
 G. Celik, S. Ailawar, H. Sohn, Y. Tang, F. Tao, J.T. Miller, P.L. Edmiston, U.S. Ozkan, Swellable Organically-modified Silica (SOMS) as a Catalyst Scaffold for Catalytic Treatment of Water Contaminated with Trichloroethylene, ACS Catalysis, (2018).