Influence of hydrotalcite preparation conditions on its physico-chemical properties

Abstract

The aim of the research was to prepare and characterize hydrotalcite synthesized under different preparation conditions. The most common hydrotalcite preparation is the co-precipiaton method. The preparation process strongly influences the catalytic properties of hydrotalcite; therefore, optimal conditions have to be determined. During the study, seven samples of the catalyst were prepared in the pH range from 8 to 12 and the synthesis temperature range from 25 to 55 °C. Based on several catalyst properties, optimal synthesis pH 10 was found. Ideal temperature of the preparation was determined to be 35 °C, but the temperature does not have a significant effect on the catalyst properties.

Impact of Hydrotalcite’s Basic Sites on the Catalyst Stability and the Branching Selectivity in α-Hydroxyketone Aldolization

“…81 This is in line with the enhanced porous characteristics of the rehydrated hydrotalcite (number/diameter of the mesopores, thus the accessibility of basic sites) due to its distorted layered structure as shown by the XRD, BET, and SEM experiments. 82 Considering the abundance of Bro̷ nsted basic sites in RHT-NaOH, confirmed by CO 2 -TPD as well as CDCl 3 −FT-IR experiments, we propose that the newly created OH − groups in the interlayer of the catalyst upon rehydration (Bro̷ nsted base) serve as active basic sites, playing a leading role in the aldolization of DHA. Our experimental data clearly show that the OH − ions on the surface of HT exhibit greater reactivity compared to isolated OH − ions (NaOH).…”

“…The obtained results attest that RHT-NaOH has advantages over homogeneous catalysts as well as HT-C, as it ensures higher catalytic activity and selectivity (Figure ). This is in line with the enhanced porous characteristics of the rehydrated hydrotalcite (number/diameter of the mesopores, thus the accessibility of basic sites) due to its distorted layered structure as shown by the XRD, BET, and SEM experiments . Considering the abundance of Bro̷nsted basic sites in RHT-NaOH, confirmed by CO 2 -TPD as well as CDCl 3 –FT-IR experiments, we propose that the newly created OH – groups in the interlayer of the catalyst upon rehydration (Bro̷nsted base) serve as active basic sites, playing a leading role in the aldolization of DHA.…”