Synthesis and characterization of triflic acid-functionalized mesoporous Zr-TMS catalysts: heterogenization of CF3SO3H over Zr-TMS and its catalytic activity

Triflic acid-functionalized Zr-TMS (zirconium oxide with a mesostructured framework; TMS, transition metal oxide mesoporous molecular sieves) catalysts have been synthesized by functionalizing triflic acid onto the walls of Zr-TMS via post synthesis method. The synthesized materials were characterized by powder XRD, N2-sorption, FT-IR spectroscopy, elemental analysis, solid-state 13C CP and DD/MAS NMR spectroscopy, FT-Raman analysis, NH3-TPD, SEM, TEM, TG-DTA, and DTG techniques. All these results revealed that an ordered Zr-TMS material was synthesized and triflic acid was anchored on the walls of the Zr-TMS. Typical XRD patterns of the Zr-TMS and functionalized Zr-TMS (f-Zr-TMS) showed ordered structures. Synthesized materials showed type IV isotherms. The chemical shift observed (˜119 ppm) and 13C–19F coupling (JC–F˜310 Hz) by 13C DD/MAS NMR showed that the triflic acid was intact on the catalyst framework. According to Raman spectral analysis, triflate was adsorbed on the zirconia surface at all loadings as a tridentate ligand through three equivalent S---O bonds (local C3v symmetry). Ammonia TPD measurements revealed an increase in number of acid sites with an increase in loading of triflic acid. Functionalized amorphous Zr---O---SO2---CF3 catalysts were also synthesized by an in situ method and SO42-/ZrO2 was obtained for comparison. The catalytic activity of the materials was tested in the acetalization of ethylacetoacetate and in the benzoylation of biphenyl in a batch reactor at 100 and 150 °C, respectively. Recycling was performed in the acetalization of ethylacetoacetate using f-Zr-TMS-30 three times and no major deactivation of the catalyst was observed.