Nanocrystalline MgO as a dehydrohalogenation catalyst

Abstract Nanocrystalline MgO has been found to be an efficient dehydrohalogenation catalyst. Its reaction with different chlorobutane isomers or 1-bromobutane results in topochemical transformation of the MgO phase to MgCl 2 or MgBr 2 accompanied by a sharp decrease in the catalyst surface area and increase in its activity. The resulting magnesium chloride and magnesium bromide are very active catalysts for HCl and HBr elimination from halogenated hydrocarbons. The reaction mechanism changes from predominantly E2 elimination on MgO to mostly E1 elimination over MgCl 2 and MgBr 2 , which act as Lewis acids. It was also found that MgBr 2 could be completely converted back to MgO by calcination in oxygen at 500°C while MgCl 2 oxidation did not occur under similar conditions.

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