One-step oxidehydration of glycerol to acrylic acid using ETS-10-like vanadosilicates

Vanadosilicates isostructural to ETS-10 and AM-6 microporous materials were synthesized hydrothermally using derivatives of cis- and trans-3,5-dimethyl-piperidine as organic structure directing agents (SDAs) and were subsequently tested as heterogeneous catalysts for the oxidehydration of glycerol to acrylic acid. The best performances were obtained with vanadosilicates prepared with 1,1,3,5-tetramethyl piperidinum cations, which were capable of converting 93.6% of glycerol to acrylic acid in one step, with 85.4% selectivity. Other important chemicals such as acrolein (3.8%), propanal (2.3%), acetaldehyde (3.2%), acetic acid (2.5%), and propionic acid (1.4%) were produced in smaller amounts. The results clearly indicated that these vanadosilicates are potential multifunctional catalysts capable of performing the oxidehydration of glycerol to acrylic acid in a single step. Spectroscopic data obtained from ⁵¹VMAS-NMR, UV-Vis, XPS, and Raman scattering analyses suggested that the selectivity of these vanadosilicates for the oxidative dehydration of glycerol to acrylic acid could be attributed to the capacity of the vanadium species for dynamic adoption of multiple oxidation states during the catalytic reaction.