Synthesis and characterization of titania-based ternary and binary mixed oxides prepared by the sol-gel method and their activity in 2-propanol dehydration

Single oxides of titania, silica, alumina, and zirconia were synthesized by the sol-gel method, using a temperature treatment before hydrolysis. Binary and ternary oxides of titania-alumina, titania-silica, titania-zirconia, titania-zirconia-alumina, and titania-zirconia-silica were similarly prepared. The synthesized oxides were analyzed by nitrogen adsorption, XPS, XRD, AAS, and TEM, to assess their physicochemical characteristics. The mixed oxides showed nearly identical textural properties, independent of the composition. Only the titania-silica mixed oxide presented anatase domains as determined by XRD. However, crystal segregation in some other mixed oxides was detected by TEM. XPS revealed that the surface atomic distribution in the solids was close to the bulk composition that was obtained by AAS. Furthermore, the binding energies determined by XPS were similar to those previously reported for homogeneous systems. The synthesized systems were tested in the 2-propanol dehydration reaction, where the silica-containing materials were found to present the highest activity. In the ternary systems, Al seemed to interact marginally with the Ti and Zr cations, whereas interaction with Si was evidenced by an increase in 2-propanol dehydration activity and by binding energy shifts for all of the cations.