The role of ZnO in the catalytic behaviour of Zn-Al mixed oxides in aldol condensation of furfural with acetone

Reconstruction of the ZnAl Mixed Oxides Into the Layered Double Hydroxide Catalysts Active in the Aldol Condensation of Furfural: The Role of ZnO Particles

“…In-situ DR UV-VIS spectroscopy was performed using a spectrophotometer (Evolution 300, Thermo Scientific) equipped with a DR accessory containing a reaction chamber (The Praying Mantis, Harrick) (Smolakova et al, 2018;Dubnová et al, 2021). The DR spectra of the corresponding ZnAl LDHs were recorded in a He flow at temperatures ranging from 25 to 400 °C; the temperature was constant for 4 h, after which the temperature was decreased to 50 °C, and the rehydration of materials was conducted using home-made equipment.…”

“…The mixture was cooled to 25 °C, saturated with CO 2 (10% CO 2 in He atmosphere at 15 ml/min) for 30 min, and purged with He (25 ml/min), to remove physisorption molecules. Finally, desorption was performed at a heating rate of 10 °C/min at a temperature range of 25-900 °C. The TPD-CO 2 of the ZnAl mixed oxides was conducted as previously mentioned (Smolakova et al, 2018;Dubnová et al, 2021).…”

“…This is a fundamental difference compared to the corresponding LDHs containing either crystalline LDH or ZnO structures (ZnAl-1.9K-REH) or a pure crystalline LDH structure (ZnAl-X-HT with a Zn/Al molar ratio of 1.0-4.4 and ZnAl-1.9U-HT). The details are shown in the XRD patterns of the corresponding ZnAl LDHs (Supplementary Figure S1, Supplementary Table S1) and ZnAl mixed oxides of the corresponding materials (Supplementary Figure S1, Supplementary Table S2) or our previous studies on ZnAl mixed oxides (Smolakova et al, 2018;Dubnová et al, 2021).…”

“…ZnAl RE-LDHs with various properties were prepared by three different syntheses of the original ZnAl LDHs: Jiang et al (2010), Kovanda et al (2010), Liu et al (2014). This follows our previous study describing the transformation of ZnAl-LDH into corresponding ZnAl mixed oxides (Smolakova et al, 2018) and the catalytic behaviour of ZnAl mixed oxides in the aldol condensation of furfural (Dubnová et al, 2021).…”

Understanding the effect of co-reactants on ketonization of carboxylic acids in the aqueous-phase pyrolysis oil of wood

“…Aldol condensation reaction is a well-known C-C bond formation reaction, and many studies have been carried out to produce liquid fuel intermediates using various model compounds such as furfural (FF, C 5 H 4 O 2 ) and acetone (C 3 H 6 O) (Su et al 2017;Dubnová et al 2020). In this case, carboxylic acids (RCOOH) should be removed or be limited from the reactants prior to the aldol condensation reaction, because of the stability of the basic catalysts such as MgO and hydrotalcites.…”