Acetalization of acetone with glycerol catalyzed by niobium-aluminum mixed oxides synthesized by a sol–gel process

Niobium-aluminum-based catalysts were synthesized by a sol–gel process and successfully applied to the reaction of acetalization of acetone with glycerol yielding 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal) and 2,2-dimethyl-1,3-dioxan-5-ol. The synthesis procedure was developed using high-throughput techniques and the materials prepared with molar ratio1 Metal (1Nb:xAl): 100H2O: 1.5NH4OH (in which x = 1, 0.6, 0.3, 0.1 and 0.05) were selected to be further investigated. The obtained series of mixed oxides displayed high catalytic activity reaching glycerol conversion up to 84%, with 98% of selectivity towards solketal. The physicochemical properties of the investigated catalysts were characterized by N2-adorption/desorption, thermal analysis, X-rays diffraction, FTIR and Raman spectroscopy, and by adsorption of pyridine monitored by FT-IR spectroscopy and TGA. The catalysts are truly heterogeneous and can be reused in consecutive runs without loss of activity.