Recent progress in one-step synthesis of acrylic acid and methyl acrylate via aldol reaction: Catalyst, mechanism, kinetics and separation

High-efficiency and durable V-Ti-Nb ternary catalyst prepared by a wet-solid mechanochemical method for sustainably producing acrylic acid via acetic acid-formaldehyde condensation

Based on the precise phase control V species adjustment of vanadium phosphorus oxides (VPOs), a series of metal oxides (Nb₂O₅, MoO₃, WO₃, and Bi₂O₃) were selected as modification agents to further enhance the catalytic activity and retain the excellent durability of VPO-TiO₂-based catalysts for the new procedure of producing acrylic acid via acetic acid-formaldehyde condensation. At an elevated liquid hourly space velocity (LHSV), the (AA + MA) selectivity reached 92.3% with a (MA + AA) formation rate of 63.8 μmol^-1 g_cat ^-1 min^-1 over the Nb-decorated catalyst (catalyst VTi-Nb), and it maintained good durability for up to 100 h. The detailed characterization results of XRD, Raman, XPS, NH₃-TPD, CO₂-TPD, and H₂-TPR, demonstrated that the addition of Nb₂O₅ could observably enhance the catalytic efficiency of the VPO-TiO₂ catalyst. It not only improved the catalyst durability by enhancing prereduction of the V⁵⁺ species, but also enhanced the active site density to improve the catalytic activity.