Publication detail

On the influence of synthetic parameters on the properties and aldol condensation performance of the MgAl mixed oxides and rehydrated hydrotalcites

Year: 2024

Type of publication: článek v odborném periodiku

Name of source: Applied Clay Science

Publisher name: Elsevier Science BV

Place: Amsterdam

Page from-to: 107263

Titles:

Language	Name	Abstract	Keywords
cze	Vliv parametrů syntézy směsných oxidů MgAl a rehydratovaných hydrotalcitů na jejich vlastnosti a výkon v aldolové kondenzace	Vysoká katalytická aktivita směsných oxidů MgAl (MO) a rehydratovaných hydrotalcitů (HTC) z nich v posledních desetiletích učinila velmi slibné základní katalyzátory pro různé organické reakce. Postup syntézy i mechanismus tvorby struktury HTC je dobře popsán. Navzdory tomu bylo málo publikováno o tom, jak syntetické parametry ovlivňují fyzikálně-chemické vlastnosti, schopnost rehydratace a výkonnost katalyzátorů odvozených od hydrotalcitu.	parametry syntézy; směsné oxidy; MgAl; hydrotalcity; aldolová kondenzace
eng	On the influence of synthetic parameters on the properties and aldol condensation performance of the MgAl mixed oxides and rehydrated hydrotalcites	In recent decades, the high catalytic activity of MgAl mixed oxides (MOs) and rehydrated hydrotalcites (HTCs) has made them very promising basic catalysts for various organic reactions. The synthesis procedure as well as the mechanism of the formation of HTC structure has been well described. Despite this, little has been published on how synthetic parameters affect the physico-chemical properties, rehydration ability and performance of the hydrotalcite-derived catalysts. Here, a series of catalysts with the same molar ratio Mg/Al = 3 varied by the coprecipitation conditions (pH value, temperature, ageing duration) were synthesized and used as precursors for the preparation of the MgAl MOs and rehydrated HTCs. The set of methods (AAS, XRD, SEM, N2-physisorption, TGA and CO2-TPD) was used to establish a relation between the synthetic parameters and the physico-chemical properties of the prepared materials. Their catalytic performance was monitored in aldol condensation of furfural and acetone as a model reaction. Preparations at different pH values and temperature resulted in the formation of HTC samples with crystallite size evaluated by XRD in the range of 70-230 ?, (d003). Nevertheless, the crystallite size of the resulting MOs was similar in the range of 30-36 ?, (d003). The rehydration of the MOs for 5-120 min produced high-crystalline reconstructed HTC with a crystalline size in the range of 82-111 ?, (d003), i.e. the crystallite size of a large-size HTC precursor was not restored. Catalytic results revealed that the crystallite size of an as-prepared HTC precursor was a crucial parameter that affected the performance of both MOs and reconstructed HTCs in the condensation reaction. Furfural conversion over MOs and short-time rehydrated (5-10 min) materials in the reaction was strongly dependent on initial size of the as-prepared HTC crystallites. In contrast, the catalytic performance of the catalysts rehydrated for 120 min, was similar: furfural conversion was	Hydrotalcites; Rehydration; Aldol condensation; Furfural; Crystallite size

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