Estudio del mecanismo de reacción de la oxidación de isopropanol sobre óxidos mixtos de Mn-Ti mediante espectroscopía FT-IR y cromatografía de gases

Several samples of TiO2 (anatase)-supported Mn oxide have been prepared by a wet impregnation method, named as XMn- TiO2 (with X = 0.5, 1.0, 1.5 and 2.0, the theoretical monolayer fractions). All samples were characterised by conventional techniques. Mn oxide was found to be well dispersed on the support surface as Mn3+species, while part of it is stabilised into the TiO2 bulk as Mn4+ species. These materials are stable in the 600-900 K range and retain medium-high average specific surface area of ~ 80 m2/g. From the catalytic point of view, they are less active than pure Mn oxides, Mn2O3 y Mn3O4, in the isopropanol oxidation but, above 600 K, reach complete oxidation of isopropanol to CO2 and depending on the Mn content become more selective to propilene. FT-IR studies and the GC-MS analysis confirm the catalytic test results allowing to detect some intermediate products, as formates and esthers, and so to propose the following 2-propoxide/acetate/formate surface pathway for the 2-propanol total oxidation.