Mechano-chemical versus co-precipitation for the preparation of Y-modified LDHs for cyclohexene oxidation and Claisen-Schmidt condensations

Pavel, Octavian Dumitru; Stamate, Alexandra-Elisabeta; Zăvoianu, Rodica; Bucur, Cristina; Bı̂rjega, R.; Angelescu, E.; Pârvulescu, Vasile I.

doi:10.1016/j.apcata.2020.117797

Cited by 16 publications

(11 citation statements)

References 69 publications

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“…Both real and bulk densities of the Ce-PP sample are about two times higher compared to those of the Ce-MC sample, suggesting a significantly better packing of the former. Both samples show large surface areas as already noticed for mixed oxides obtained by calcination of corresponding LDHs modified with rare earth cations [ 12 ].…”

Section: Resultssupporting

confidence: 54%

“…Apart from the evident advantage of easy operation, this approach shows great potential to overcome the difficulties associated with solution operation, such as the different precipitation rates with pH adjustment [ 10 ]. To our knowledge, several studies have already been devoted to the synthesis of LDHs modified with different rare-earth elements through mechanochemical techniques [ 11 , 12 ]. Still, none of them have reported a LDH catalyst modified with cerium.…”

Section: Introductionmentioning

confidence: 99%

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The Influence of the Preparation Method on the Physico-Chemical Properties and Catalytic Activities of Ce-Modified LDH Structures Used as Catalysts in Condensation Reactions

et al. 2021

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Mechanical activation and mechanochemical reactions are the subjects of mechanochemistry, a special branch of chemistry studied intensively since the 19th century. Herein, we comparably describe two synthesis methods used to obtain the following layered double hydroxide doped with cerium, Mg3Al0.75Ce0.25(OH)8(CO3)0.5·2H2O: the mechanochemical route and the co-precipitation method, respectively. The influence of the preparation method on the physico-chemical properties as determined by multiple techniques such as XRD, SEM, EDS, XPS, DRIFT, RAMAN, DR-UV-VIS, basicity, acidity, real/bulk densities, and BET measurements was also analyzed. The obtained samples, abbreviated HTCe-PP (prepared by co-precipitation) and HTCe-MC (prepared by mechanochemical method), and their corresponding mixed oxides, Ce-PP (resulting from HTCe-PP) and Ce-MC (resulting from HTCe-MC), were used as base catalysts in the self-condensation reaction of cyclohexanone and two Claisen–Schmidt condensations, which involve the reaction between an aromatic aldehyde and a ketone, at different molar ratios to synthesize compounds with significant biologic activity from the flavonoid family, namely chalcone (1,3-diphenyl-2-propen-1-one) and flavone (2-phenyl-4H-1benzoxiran-4-one). The mechanochemical route was shown to have indisputable advantages over the co-precipitation method for both the catalytic activity of the solids and the costs.

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Section: Resultssupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

The Influence of the Preparation Method on the Physico-Chemical Properties and Catalytic Activities of Ce-Modified LDH Structures Used as Catalysts in Condensation Reactions

et al. 2021

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“…Traditionally, the layered catalytic materials are obtained by several methods [22], such as co-precipitation (at low or high supersaturation, urea hydrolysis), ion-exchange, rehydration using structural memory effect, hydrothermal method, secondary intercalation, etc. Other methods, which include mechano-chemical synthesis [23], exfoliation in aqueous solution [24], dry exfoliation [25], and electrochemical synthesis [26], were developed recently aiming to replace the usual methods. However, most traditional methods use inorganic alkalis (i.e., NaOH, KOH, Na 2 CO 3 , K 2 CO 3 etc.…”

Section: Introductionmentioning

confidence: 99%

An Advanced Approach for MgZnAl-LDH Catalysts Synthesis Used in Claisen-Schmidt Condensation

et al. 2022

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Using organic-base tetramethylammonium hydroxide (TMAH) is a viable, cheap, and fast option for the synthesis of MgZnAl-LDH-type materials by both co-precipitation and mechano-chemical methods. TMAH presents several advantages, such as the smaller quantity of water required in the washing step compared to the use of inorganic alkalis, the prevention of LDH contamination with alkali cations, and its action as a template molecule in texture tailoring. It also has disadvantages, such as its presence in small quantities in the resulting layered materials. Regardless of the use of organic/inorganic bases and co-precipitation/mechano-chemical methods, zincite stable phase was found in all the synthesized solids. The basicity of catalysts followed the trend: mixed oxides > reconstructed > parent LDH. The memory effect of LDH was supported only by the presence of Mg and Al cations, while Zn remained as a zincite stable phase. The catalytic activities for Claisen–Schmidt condensation of benzaldehyde with cyclohexanone provided values higher than 90% after 2 h, with a total selectivity toward 2,6-dibenzylidenecyclohexanone, while self-condensation of cyclohexanone yielded no more than 7.29% after 5 h. These behaviors depended on catalyst basicity as well as on the planar rigidity of the compound.

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“…In addition, the absence of Ti-related phases in TMA-LDH was possibly ascribed to its efficient incorporation into the framework of LDHs. This feasible alkali precipitation has also been widely adopted to synthesize pristine and doped LDHs in previous work [22][23][24][25]. Furthermore, composition analysis gives quantitative information of element distribution in the obtained products.…”

Section: Resultsmentioning

confidence: 99%

Efficient Recycling Blast Furnace Slag by Constructing Ti-Embedded Layered Double Hydroxide as Visible-Light-Driven Photocatalyst

et al. 2022

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In this work, a strategy of heat treatment-precipitation has been developed to recycle Ti-containing metallurgical solid waste by forming Ti-embedded MgAl layered double hydroxide (TMA-LDH). This facile and simple route is featured by the dedicated utilization of the composition of slag with high overall recovery efficiency. Importantly, as-obtained product exhibits visible light response distinctly different from that of pristine MA-LDH ascribed to the Fe doping inherited from initial slag. Its mesoporous nanostructure also provides more microchannels for mass and carrier transfer. As such, excellent photocatalytic activity towards degradation of tetracycline hydrochloride is achieved, and 88% removal could be obtained in 60 min. Furthermore, 44% increase in efficiency than that of Ti-excluded LDH also indicates the synergistically promoting effect of Ti incorporation. Mechanism investigation suggests that Ti incorporation regulates the electronic structure of pristine LDH with more active sites, and favors the formation of radicals with improved oxidative ability for photocatalysis.

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Mechano-chemical versus co-precipitation for the preparation of Y-modified LDHs for cyclohexene oxidation and Claisen-Schmidt condensations

Cited by 16 publications

References 69 publications

The Influence of the Preparation Method on the Physico-Chemical Properties and Catalytic Activities of Ce-Modified LDH Structures Used as Catalysts in Condensation Reactions

The Influence of the Preparation Method on the Physico-Chemical Properties and Catalytic Activities of Ce-Modified LDH Structures Used as Catalysts in Condensation Reactions

An Advanced Approach for MgZnAl-LDH Catalysts Synthesis Used in Claisen-Schmidt Condensation

Efficient Recycling Blast Furnace Slag by Constructing Ti-Embedded Layered Double Hydroxide as Visible-Light-Driven Photocatalyst

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