Synthesis of quaternary metal oxides immobilized on APTMS-coated magnetite: an efficient and reusable nanocatalyst for Knoevenagel condensation under green conditions

A simple, green and highly efficient procedure has been developed for Knoevenagel condensation of malononitrile and aromatic aldehydes to the corresponding benzylidenemalononitriles in the presence of Fe3O4@APTMS@Zr-Sb-Ni-Zn nanoparticles (NPs) as a durable nanocatalyst. The heterogeneous nanocomposite was prepared by immobilization of Zr-Sb-Ni-Zn mixed metal oxides on APTMS-coated magnetite. The synthesized catalyst was characterized using Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), vibration sample magnetometer (VSM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET). In this approach, the condensation of malononitrile and aromatic aldehydes were done in water under reflux conditions to give the corresponding products within 3-60 minutes in 89-95% yields. The magnetically recoverable catalyst was recycled and reused about four times without remarkable loss of activity. This method offers various benefits such as mild and eco-friendly reaction conditions, short reaction times and high purity of products, excellent efficiency and use of water as green solvent, reusability and recoverability of the nanostructure catalyst.

Magnetically recoverable nanostructured Pd complex of dendrimeric type ligand on the MCM-41: Preparation, characterization and catalytic activity in the Heck reaction

A palladium complex of a dendrimer type ligand of aminoethylacrylamide immobilized onto the mesoporous channels of MCM-41 with magnetic core was prepared and characterized using various techniques such as XRD, TEM, BET, FT-IR, TGA, and VSM. The prepared nanostructured material was found as a magnetically recoverable catalyst for Heck reaction of aryl halides and vinylic C–H. The catalyst is easily recoverable with an external magnet and is reusable with different leaching amounts depending to loading of Pd. A hot filtration test was also performed and gave evidence that Palladium in heterogeneous samples can dissolve and then redeposit on the surface of the support material.

Synthesis of heterocyclic compounds by catalysts supported on nano-magnetite (Fe3O4)-an update

: Magnetic nanoparticles have attracted a great deal of attention from both academic and industrial stand point of view, owing to their unique properties including high surface area, and superparamagnetism, which enable them to be suitable for modification with many compounds and employing them as catalyst in organic reactions. In this mini review, we have summarized the application of surface modified magnetite nanoparticles as magnetically recoverable catalyst in heterocyclic synthesis. These catalysts include silica, biopolymer, acid, amine, transition metal, ionic liquid and metal organic framework supported magnetite catalysts.

MAGNETICALLY RECOVERABLE POLYMER CATALYST FOR CELLULOSE HYDROGENOLYSIS

A new type of Ru-containing magnetically recoverable catalyst based on a polymer matrix of hypercrosslinked polystyrene (HPS) for the reaction of the hydrogenolysis of microcrystalline cellulose to ethylene and propylene glycol (EG and PG) is proposed. The catalyst is synthesized sequentially in two stages. At the first stage, by means of thermal decomposition of iron (III) salts in the presence of polyols, magnetite particles (Fe3O4) are formed in the pores of the HPS. At the second stage, Ru-containing nanoparticles of the active phase of the catalyst are synthesized on the surface of Fe3O4/HPS. Samples of the original HPS, Fe3O4/HPS and Ru-Fe3O4/HPS were characterized using various physicochemical methods. In particular, it was shown that the synthesized samples of catalysts have a high specific surface area (450 - 750 m2/g, depending on the magnetite content), retain the micro-mesoporous nature of the original polymer, and have a high saturation magnetization (4.0 ± 0.5 emu /g), which makes them easy to separate from the reaction mass by an external magnetic field. According to the results of transmission electron microscopy (TEM), the average diameter of the nanoparticles of the active phase Ru was 2.0 ± 0.5 nm. The hydrogenolysis of cellulose to glycols was carried out under the following conditions: 255 °C; 60 bar H2; 55 min; 0.3 g of cellulose; 0.07 g of catalyst 3% Ru-Fe3O4/HPS; 30 ml of H2O; 0.07 g of Ca(OH)2. Under these conditions, the selectivities for EG and PG were 22.6 % and 20.0 %, respectively. The degree of cellulose conversion reaches 100 %. The catalyst showed good stability under hydrothermal reaction conditions, is easily separated from the reaction mass by an external magnetic field, and can be used in the processes of cellulose-containing biomass conversion.