Knowledge Bank

As many parts of the world face water shortages, it is essential to find ways to decontaminate groundwater contaminants like the volatile compound trichloroethylene (TCE). A hydrodechlorination (HDC) reaction could treat this carcinogen by reducing the chlorinated hydrocarbon with hydrogen over palladium metal to produce ethane gas and hydrochloric acid. In order to protect the active metal from anionic poisons like chlorine and sulfur present in groundwater, a novel compound called swellable organically modified silica (SOMS) has been proposed as a possible catalytic support due to its hydrophobicity. However, SOMS is not thermally stable and cannot be used in reactions requiring high operating temperatures. This study examines the effects of fully saturating the material with acetone and calcining it instantly at high temperature (H-SOMS) prior to impregnating palladium catalyst to improve the thermal stability. In order to understand the chemical and physical properties of the H-SOMS, nitrogen physisorption, temperature programmed decomposition (TPD), and CO chemisorption were utilized. The steady-state gas-phase HDC of TCE catalytic activity experiments were performed in a fixed-bed reactor using gas chromatography (GC) to identify and quantify reaction products. These methods showed that the instant heat treatment changed the textual properties of SOMS and increased the accessibility of CO to the Pd sites. The palladium catalyst supported on the H-SOMS did achieve better conversion than original SOMS support (from 38% to 93% at 200⁰C). These promising results reveal H-SOMS would make an effective catalytic support for HDC reactions operating at high temperatures. Using this discovery, the cost of water treatment plants could potentially be reduced due to the better utilization and protection of the active metal. Increasing the feasibility of eliminating volatile chlorinated hydrocarbons could result in cleaner and safer drinking water.