Synthesis of Nanocrystalline Mg-Al Hydrotalcites in the Presence of Starch—the Effect on Structure and Composition

Abstract

The study describes the synthesis of Mg-Al hydrotalcite (Ht) with the use of starch as a structure controlling biotemplate. Syntheses were carried out at room temperature, by co-precipitation at pH = 10. The investigated synthesis parameters included the nature of the precipitating agent (NaOH/Na2CO3 or NH3aq/(NH4)2CO3), the nature of starch (potato, corn and cassava), the method of starch addition to reagents, the method of drying and the effect of washing. The materials were examined with X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy and infrared spectroscopy. The data show that synthesis of Ht materials in the presence of starch, with use of the ammonia-based precipitant, enabled preparation of nanocrystalline Ht with very fine (<50 nm) particle size. All investigated starches had a similar effect on the crystallinity and the grain size of Ht precipitates. Ht with the smallest nanocrystals was obtained when starch was present in all solutions used for synthesis, and the final product subjected to freeze drying. Washing with water was found to enhance recrystallization and exchange of nitrates for carbonates. Infrared spectra showed that an interaction exists between the biopolymer template and the Ht particles, resulting in a higher degree of order within the Ht-adhering starch component.

CO2 Hydrogenation to Methane over Ni-Catalysts: The Effect of Support and Vanadia Promoting

“…The impregnation was sufficient to prepare the catalysts of nominal V 0.5 wt % (V 2 O 5 content of 0.88 wt %). The samples were dried at 393 for 12 h and subsequently calcined at 773 for 3 h. The NiWP sample was synthesized by the co-precipitation method, which is routinely employed in the synthesis of hydrotalcite-like materials [22][23][24][25][26][27][28][29]. First, Ni(NO 3 ) 2 •6H 2 O and Al(NO 3 ) 3 •9H 2 O were dissolved in deionized water (135 mL) at a molar ratio of M 2+ /M 3+ of 0.35, i.e., much lower than in the natural hydrotalcite (M 2+ /M 3+ = 3), so that the excess Al could form, after calcination, as an alumina support.…”

Special Issue: Layered Double Hydroxides (LDH) and LDH-Based Hybrid Composites

“…The use of additional molecules in the synthesis routes of LDH helps to control their properties. The study by Michalik et al [ 14 ] showed the effects of using starch as a structure-controlling biotemplate. This approach enabled the preparation of nanocrystalline Mg/Al LDH with a very fine (<50 nm) particle size.…”

Bio-DEE Synthesis and Dehydrogenation Coupling of Bio-Ethanol to Bio-Butanol over Multicomponent Mixed Metal Oxide Catalysts

“…The mineral hydrotalcite itself is a magnesium-aluminum hydroxycarbonate with the general formula [Mg 6 Al 2 (OH) 16 ]CO 3 *4H 2 O [38,40,48]. The HT family includes many isost××ructural and polytype forms [38][39][40]48,49]. Their properties can be tailored through cation and anion exchange in the precursor framework [49][50][51].…”

“…The HT family includes many isost××ructural and polytype forms [38][39][40]48,49]. Their properties can be tailored through cation and anion exchange in the precursor framework [49][50][51]. The possibility of modifying the cations or their ratios and the interlaminar anion makes these materials a very versatile system with desirable catalytic properties.…”

“…The possibility of modifying the cations or their ratios and the interlaminar anion makes these materials a very versatile system with desirable catalytic properties. The adjustment of the acidic or basic properties of LDHs or mixed oxides that are generated by calcination at high temperatures has recently been studied [38][39][40][41][42][43][44][45][46][47][48][49][50][51].…”