Magnesium-containing mixed oxides as basic catalysts:: base characterization by carbon dioxide TPD-MS and test reactions

A set of catalysts has been prepared consisting of both pure magnesia and zirconia as well as magnesia-zirconia and magnesia-titania mixed oxides. The basic sites density was determined for all solids from the temperature-programmed desorption of CO2. Results indicate that magnesia-titania mixed oxides are the most basics followed by magnesia-zirconia, then pure zirconia and, finally, pure magnesia catalysts. Moreover, four test reactions for acid-base characterization of solids were used: 2-methyl-3-butyn-2-ol reaction, propan-2-ol transformation, allylbenzene isomerization and the Aldol condensation of acetone. Although the 2-methyl-3-butyn-2-ol test reaction showed a 100% selectivity to basic products (acetylene and acetone), we were not able to establish a scale of basicity for the catalyst tested. Similar results were obtained for the 2-propanol test reaction. As a final conclusion we can state that although all test reactions gave results according to the basic character of the catalysts. only the Aldol condensation of acetone and allylbenzene isomerization are sensitive enough to establish a basicity scale of the catalyst according to the CO2 TPD-MS experiments. (C) 2004 Elsevier B.V. All rights reserved.