Morphology induced CO, pyridine and lutidine adsorption sites on TiO2: Nanoparticles, nanotubes and nanofibers

Anatase with nanotubular (NT) and nanofibrilar (NF) morphology was obtained by annealing treatment at 773 and 873 K of a hydrous titanate with nanotubular morphology synthesized by alkali hydrothermal method. The surface properties were compared with those of a commercial anatase made up of nanoparticles (NPs); materials with similar specific surface area were selected for this end. Low temperature CO adsorption FTIR showed only one adsorption site on the OH groups of nanotubes and nanofibers and almost no Lewis sites were detected suggesting the absence of coordinatively unsaturated Ti4+ sites in NT and NF samples. All the OH groups on anatase nanotubes are exposed on the surface, and they are not of Brönsted type. The OH groups in NT and NF adsorb 2.2 times pyridine or lutidine molecules than nanoparticles via H-bonding interaction. These weak interactions are very attractive in the elimination of N-compounds from oil fractions using regenerable adsorbents.