Sustainable Acrylic Acid Making via Acetic Acid–Formaldehyde Condensation: The Highly Selective and Durable VPO-TiO₂ Catalyst Accomplished by VPO Phase Control and Wet Co-Mechanical Milling

Abstract

On the basis of the precise phase control of vanadium phosphorus oxides (VPOs), nanosized TiO 2 was employed as a dopant/dispersant to fabricate a series of VPO-TiO 2 catalysts through a wet mechanical co-milling process. The resulting catalysts showed outstanding durability plus excellent target products [acrylic acid (AA) + methyl acrylate (MA)] selectivity via acetic acid (HAc)−formaldehyde (FA) condensation. Over an optimized catalyst of 20% VPO-TiO 2 , the (AA + MA) selectivity being 85% (HAc input-based) at a yield level >60% (FA input-based) can be achieved after 180-h running, the best known to date over the VPObased catalysts. The detailed characterizations including X-ray powder diffraction, Raman spectra, XPS, and H 2 -TPR indicated that the V 5+ in the original VOPO 4 phase would be partially reduced in the presence of TiO 2 after the milling process in the cyclohexane medium; and the partially reduced VOPO 4 phase together with the decorated TiO 2 component stabilized the remaining V 5+ entities and considerably slowed down the continuous reduction of surface V 5+ species, accounting for substantially enhanced catalyst durability as well as target product selectivity. The NH 3 -/CO 2 -TPD results demonstrated that the surface acid−base property also varied notably with the VPO content which in turn controlled the HAc conversion and (MA + AA) selectivity accordingly.

Influence of Al Oxides on Cs-SiO2 Catalysts for Vapor Phase Aldol Condensation of Methyl Acetate and Formaldehyde

“…Methyl acrylate (MA), as a fundamental chemical raw material, is widely applied in numerous commercial processes, especially in the production of plastics, adhesives, paints, PAN fibers, biomimetic materials, etc. − A multitude of ways have emerged for the synthesis of MA in the past few decades. Among them, the two-stage oxidation of propylene is the primary route to fabricate the acrylic acid (AA) and MA in the commercial production. , However, an ever-increasing crude oil price induces an increase of costs for this petroleum-based process as the propylene feedstock is closely dependent on the limited petroleum resources .…”

“…In early years, Ai reported that V–P binary oxides and V–Ti binary phosphate could catalyze the aldol condensation of acetic acid (Aa) and FA to prepare AA. , Afterward, Ji and co-workers investigated comprehensively the preparation of VPO catalysts with efficient catalytic performance to the production of methyl acrylate and acrylic acid through the aldol condensation reactions. , Recently, this team synthesized the VPO-TiO 2 catalysts by a wet mechanical comilling method. The (AA + MA) selectivity of 85% and HAc conversion of 29–31% (HAc input-based) were obtained over an optimized catalyst of 20% VPO-TiO 2 . Additionally, Yang et al investigated the impact of metal ions on bulk VPO catalysts, and the VPO-2%Zr catalysts exhibited the highest performance.…”

“…The (AA + MA) selectivity of 85% and HAc conversion of 29−31% (HAc input-based) were obtained over an optimized catalyst of 20% VPO-TiO 2 . 1 Additionally, Yang et al 12 investigated the impact of metal ions on bulk VPO catalysts, and the VPO-2%Zr catalysts exhibited the highest performance. A series of carriers, such as ZrO 2 , γ-Al 2 O 3 , TiO 2 , SiO 2 , SBA-15, HZSM-5, and so on were used to fabricate supported VPO catalysts, the catalytic performance of which were evaluated as well.…”

“…1 at 200 °C and 350 °C, respectively. -ray photoelectron spectroscopy (XPS) was employed to analyze the chemical state of active sites on the catalyst surface, which was carried out on an ESCALAB 250Xi electron spectrometer equipped with Al Kα radiation.…”

Synthesis of acrylic acid through aldol condensation of acetic acid with formaldehyde catalyzed by Bi‐,W‐ and Cs‐doped B2O3/SiO2 nanocomposites

“…In addition to the alkali-based catalyst, vanadium-phosphorusoxide (V-P-O) also has an appreciably catalytic activity in the aldol condensation reaction. 3,[10][11][12][13] When V-P-O oxides catalyzed the aldol condensation reaction between acetic acid and formaldehyde with an acetic acid/formaldehyde molar ratio of 2.5:1 at 340 °C in a fixed-bed reactor, the total formation rate of both methyl acrylate and acrylic acid reached 11 μmol g cat −1 min −1 at the formaldehyde conversion of 60%. 10 On a ⊐-VOPO 4 /γ-VOPO 4 (w/w, 3/1) catalyst at 360 °C, the total yield of acrylic acid and methyl acrylate reached 84.2% at the formation rate of acrylic acid and methyl acrylate of 1.71 mmol g −1 h −1 .…”