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

Abstract

BACKGROUND: Acrylic acid commercially produced by the successively catalytic oxidation of propylene has a high cost. The synthesis of acrylic acid by aldol condensation between coal derivatives, acetic acid and formaldehyde, is an economic alternative to the propylene oxidation process. However, the development of an environmentally friendly and effective catalyst has remained a challenge. RESULTS: Diboron trioxide [B 2 O 3 (6-20%)]/silica (SiO 2 ) nanocomposites with B 2 O 3 particle sizes of 1-2 nm prepared by the wetness impregnation of boric acid into silica aerogel and subsequent calcination at 500 °C effectively catalyzed the gas-phase aldol condensation reaction between acetic acid and formaldehyde (trioxymethylene) to acrylic acid with a selectivity of ≈87% at 340-400 °C. Bismuth (Bi-), tungsten (W-) and caesium (Cs)-doped B 2 O 3 /SiO 2 nanocomposites had higher catalytic activities in the gas-phase aldol condensation reaction to acrylic acid than the undoped B 2 O 3 /SiO 2 nanocomposite. CONCLUSION: Weak-strength Lewis acid and alkali sites of the B 2 O 3 (6-20%)/SiO 2 nanocomposites co-catalyzed the aldol condensation reaction to form acrylic acid. The doping of B 2 O 3 /SiO 2 nanocomposites with Bi, W and Cs components results in the formation of BiBO 3 , WO 3 and CsBO 2 phases, which lead to an increase in acidity and basicity resulting in higher catalytic activity in the formation of acrylic acid.

Highly dispersed Cs2O/SiO2 catalysts for selective intramolecular dehydration of ethylene glycol monoethyl ether to ethyl vinyl ether

“…7(a), the only desorption peak observed at around 124 °C in the profile for pure SiO 2 support was ascribed to the weak acidic sites due to Si–OH on the surface of SiO 2 . 43,44 However, the location of the weak acid sites shifted to lower temperature after impregnation of Cs 2 O because of the partial substitution of H with Cs in Si–OH. In Fig.…”

Solvent-free cross aldol condensation of aldehydes and ketones over SrMo1-xNixO3-δ perovskite nanocrystals as heterogeneous catalysts

“…Moreover, they are in homogeneous solution, which makes them hard to recycle. Heterogeneous metal oxide catalysts, such as metals supported on modified silica [ [15] , [16] , [17] , [18] , [19] , [20] ], hydrotalcite [ 15 ], zeolites [ 21 ] and other metal oxides [ [22] , [23] , [24] ], however, the require addition of a co-catalyst and/or scavenger molecules, they are done at high temperatures, and they also require a hefty amount of time to run to completion [ [25] , [26] , [27] , [28] ].…”

Continuous production of methyl acrylate and acrylic acid via co-activation reaction of aldehyde condensation and esterification catalyzed by siloxane-functionalized vanadium phosphorus oxide-TiO2 catalyst

“…The highest yield of target products (MA and AA) reached 37.2 μmol g −1 min −1 . Wang et al 18 promoted a range of Bi-, W- and Cs-doped B 2 O 3 /SiO 2 catalysts for the aldol condensation reaction of HAc with HCHO supported by wetness impregnation method. The (MA + AA) selectivity reached 87%.…”