Haloethane Reactions over the Chromia Cr₂O₃ (1012) Surface

• Main Author: Ma, Qiang
• Other Authors: Chemical Engineering
• Format: Others
• Published: Virginia Tech 2014
• Subjects: dissociation; ethyl chloride; metal oxide; hydrogenation; chromium (III) oxide; dehydrogenation; haloethane; ethyl iodide
• Online Access: http://hdl.handle.net/10919/34754; http://scholar.lib.vt.edu/theses/available/etd-08252005-144859/

Ethyl iodide and ethyl chloride have been used as reactants to produce ethyl fragments on the stoichiometric α-Cr₂O₃ (1012) surface by means of thermal dissociation. Ethyl iodide is dissociated giving iodine adatoms and ethyl fragments bound to surface Cr cation sites, while ethyl chloride is dissociated giving chlorine adatoms and ethyl fragments. No oxygenated products are observed in thermal desorption, suggesting the 3-coordinate lattice oxygen on the stoichiometric α-Cr₂O₃ (1012) surface is very stable, and no nucleophilic attack occurs at the carbon atoms on surface ethyl fragments. For both reactants, the only reaction products observed are ethylene gas (CH₂=CH₂), ethane gas (CH₃-CH₃), hydrogen gas (H₂) and halogen adatoms (Cl_ads or I_ads). In thermal desorption experiments, all the gas phase products from ethyl chloride are produced in a reaction-limited, high temperature desorption feature attributed to a rate limiting β-hydride elimination from surface ethyl fragments. Similar product desorption features are observed for the reaction of ethyl iodide. However, the reaction of ethyl iodide also produces ethylene and ethane via a low temperature, desorption-limited reaction channel. It is postulated that I adatoms produced in the reaction of ethyl iodide thermal desorption might somehow promote a low temperature route to products that Cl adatoms do not. === Master of Science