Controlling Reaction Pathways for Alcohol Dehydration and Dehydrogenation over FeSBA-15 Catalysts

In Situ Immobilized Silver Nanoparticles on Rubia tinctorum Extract-Coated Ultrasmall Iron Oxide Nanoparticles: An Efficient Nanocatalyst with Magnetic Recyclability for Synthesis of Propargylamines by A3 Coupling Reaction

This research suggests a green method for synthesizing hybrid magnetic nanocomposites that can be used as a reductant and a stabilizing agent for immobilizing metal nanoparticles (NPs). The central idea is the modification of magnetic NPs using Rubia tinctorum extract, which consists of numerous carbonyl and phenolic hydroxyl functional groups to increase adsorption of metals and chelate silver ions, and decrease the adsorption of silver ions by Ag NPs, in situ. Thus, the suggested catalyst preparation process does not require toxic reagents, additional reductants, and intricate instruments. To show the effectiveness of the plant extract in reducing and immobilizing Ag NPs, the structural, morphological, and physicochemical features of the particles are studied using Fourier-transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. One of the advantages of the suggested method is to reduce the size of the magnetic NPs from 15-20 to 2-5 nm, in the presence of the extract. Additionally, the prepared Fe3O4@R. tinctorum/Ag nanocatalyst is demonstrated to exhibit a very high activity in the catalysis of the three-component reaction of aldehydes, amines, and alkynes (A3 coupling) with good to high yields of diverse propargylamines. Moreover, the nanocatalyst can be recovered several times with no considerable leaching or loss of performance.

Reaction-Induced Self-Assembly of CoO@Cu2 O Nanocomposites In Situ onto SiC-Foam for Gas-Phase Oxidation of Bioethanol to Acetaldehyde

A high-performance SiC-foam-structured nanocomposite catalyst of CoO@Cu₂ O (i.e., 50-100 nm CoO partially covered with ca. 10 nm Cu₂ O) was engineered from nano- to macro-scales in one step for the high-throughput gas-phase aerobic oxidation of bioethanol to acetaldehyde. This special CoO@Cu₂ O nanostructure shows much higher activity/selectivity than other binary metal-oxide assemblies such as CuO_x &CoO nano-mixtures or inverse Cu₂ O@CoO nanostructures. The catalyst was facilely but exclusively obtainable by in situ reaction-induced transformation of the respective metal nitrates supported on SiC-foam into the CoO@Cu₂ O nanostructure in the reaction stream. It achieved 95 % conversion with 98 % selectivity under mild conditions and was stable for at least 150 h for a feed of 20 vol % ethanol (much higher than in the literature: 1-6 vol %) at a high EtOH weight hourly space velocity of 8.5 h^-1 . Abundant Cu₂ O-CoO interfaces and high stability of the CoO@Cu₂ O nanostructure were responsible for the high activity/selectivity and promising stability in this reaction.

Direct oxidative esterification of alcohols and hydration of nitriles catalyzed by a reusable silver nanoparticle grafted onto mesoporous polymelamine formaldehyde (AgNPs@mPMF)

Oxidative esterification and hydration of nitriles are catalyzed by a newly synthesized AgNPs@mPMF. The catalyst is well characterized and reusable.

Magnetically separable and recyclable Fe3O4-supported Ag nanocatalysts for reduction of nitro compounds and selective hydration of nitriles to amides in water

As hybrid nanostructures have become more important in many fields of chemistry, Ag nanoparticles (NPs) are being increasingly immobilized onto Fe₃O₄ microspheres in situ. Structural characterization reveals that the Ag NPs are uniformly immobilized in the Fe₃O₄ microsphere-based supports. Moreover, Ag NPs are more stable in the hybrid structure than in the naked state and show high catalytic activity for the reduction of nitro compounds and hydration of nitriles to amides in water. The Fe₃O₄ microspheres were recycled several times using an external magnet.