Dehydrochlorination of 1-Chlorobutane Over Nanocrystalline MgO: The Role of Electron-Acceptor Sites

Nanocrystalline MgO aerogels possess high surface areas and outstanding reactivity with respect to variety of harmful organic substances. The catalytic activity of MgO aerogels in dehydrochlorination of 1-chlorobutane substantially increases with time due to partial MgO conversion to MgCl₂. This catalytic activity increase and surface area decrease indicate that more active catalytic sites are formed on the surface during this reaction. The catalytic activity was found to increase significantly during the 1-chlorobutane dehydrochlorination reaction, which is accompanied by the MgO modification with chloride ions. The activation energy of this reaction over partially chlorinated MgO was found to be equal to 135 kJ/mol at T < 225 °C and 63 kJ/mol at T > 225 °C. For the first time the concentrations of electron-acceptor sites were measured during a catalytic reaction. No electron-acceptor sites were observed on the surface of initial AP–MgO samples. They appeared only during the reaction. A good correlation was observed between the catalytic activity and the concentration of weak electron-acceptor sites tested using perylene. The obtained results indicate that they may be the active sites accounting for 1-chlorobutane dehydrochlorination in the active state of the catalyst.