Microwave-Assisted Solvothermal Synthesis of Fe3O4/CeO2 Nanocomposites and Their Catalytic Activity in the Imine Formation from Benzyl Alcohol and Aniline

Abstract

Fe3O4/CeO2 nanocomposites were synthetized by coating magnetite seeds of different morphologies (hexagonal, spheroidal, quasi-spherical) with ceria, in ethylene glycol as solvothermal solvent. The synthesis was performed in the presence of microwave irradiation aiming to overcome the common disadvantages proper of the classic solvothermal/hydrothermal procedure. The obtained nanocomposites were calcined at the optimum temperature of 550 °C. The structure of the new nanomaterials was carefully investigated by IR, XRD, SEM, EDS and TEM analyses. The nanocomposites resulted to be constituted by CeO2 nanoparticles distributed onto Fe3O4 seeds, that kept their pristine morphology. The new materials were used as catalysts for imine synthesis from benzyl alcohol and aniline. The highest imine conversion rate was obtained with Fe3O4/CeO2, which was synthesized from Fe3O4 nanoparticles (hexagonal) obtained by microwave hydrothermal procedure in the absence of any organic additive (polyvinylpyrrolidone, trisodium citrate dihydrate or oleic acid). The catalyst could be easily removed from the reaction mixture with the help of an external magnet, and it was recycled for at least five runs with increasing catalytic activity.

Synthesis and Use in Catalysis of Hematite Nanoparticles Obtained from a Polymer Supported Fe(III) Complex

“…[49] In this case, the presence of organic residues might hamper the migration of the substrates towards the catalytic centres, thus lowering the final yields, as already observed, for example, for ceria-based nanocomposites. [50] Since the nanometric hematite in Hem_400_Air turned out to be an efficient and selective catalyst for the hydrogenation of nitrobenzene and p-bromonitrobenzene, the question arises whether ore hematite is also an active catalyst for this reaction. Thus, we tested natural micrometric hematite (Nat_Hem) in the hydrogenation of p-bromonitrobenzene.…”

Facile imine synthesis under green conditions using Amberlyst® 15

“…After the incorporation of the green chemistry principles into the synthetic chemistry modus operandi, following the works of Anastas & Warner (1998), the above mentioned syntheses were improved further and rendered more eco-friendly through the use of heterogeneous catalysts such as: sulfated-TiO 2 , montmorillonite K-10 clay, sulfated nano-ordered silica and zeolites (Kumar et al, 2016;Atanassova et al, 2011;Naimi-Jamal, Ali & Dekamin, 2013;Amrutham et al, 2017). Further recently developed sustainable methodologies have been reported using irradiation techniques (Rizzuti et al, 2020). Moreover the addition of dehydrating agents such as phosphorous-pentoxide-silica have also been shown to drive the reaction to completion by removing the condensation product, ergo water (Naeimi et al, 2008).…”

CeO2 Structure Adjustment by H2O via the Microwave–Ultrasonic Method and Its Application in Imine Catalysis

“…CeO 2 is a new promising catalyst for imine synthesis, which can overcome the problems caused by traditional acid/base catalysts ( Tamura and Tomishige, 2015 ) and bring a lot of advantages, such as mild synthesis conditions and fast separation. Many research studies have focused on CeO 2 application in imine synthesis ( Geng et al, 2016 ; Long et al, 2019a ; Long et al, 2019b ; Cao et al, 2020 ; Rizzuti et al, 2020 ; Tamura and Tomishige, 2020 ), and it has been reported that CeO 2 morphologies can greatly influence the catalytic activity for imine synthesis ( Zhang et al, 2017 ; Yang et al, 2018 ; Zhang et al, 2018 ; Yang et al, 2020a ; Yang et al, 2020b ), which have a close relationship with the CeO 2 specific surface area and Ce 3+ defects.…”