Manganese Catalysts Research Articles

Biowaste carbon supported manganese nanoparticles as an active catalyst for the selective hydrogenation of bio-based aldehydes

Hydrogenation of aldehydes with heterogeneous manganese catalysts is an appealing approach for producing alcohols. In this paper, we report a novel and robust MnO/PN-800 catalyst for the hydrogenation of versatile biomass-derived platform molecules in the presence of molecular hydrogen as a reductant. The effect of catalyst concentration, the operating hydrogen pressure, and the reaction temperature on the catalyst activity was investigated in detail. Under the mild reaction conditions, the full conversion of furfuraldehyde, 5-Methyl-2-furaldehyde, and 5-hydroxymethyl-2-furaldehyde (5-HMF) to their corresponding alcohols was achieved without any by-product formation. Additionally, other aromatic aldehydes bearing fluoro, chloro, and nitro moieties were also tolerated. The fresh and spent MnO/PN-800 catalyst was thoroughly characterized using XPS, powder-XRD, HR-TEM, N2 adsorption-desorption, and Raman spectroscopy. Noteworthy, the MnO/PN-800 catalyst can be recovered by centrifugation and then reused directly in the subsequent hydrogenation reactions. Importantly the synthetic utility of this protocol up to ∼5 g-scale is realized. Finally, our novel MnO/PN-800 nanocatalyst was successfully employed for the direct synthesis of furfuryl alcohol in high yields from raw sugarcane bagasse. We believe that these findings will help to advance the manganese-catalyzed hydrogenation reactions.

Lotus leaves‐derived MnOx/biochar as an efficient catalyst for low‐temperature NH3‐SCR removal of NOx: effects of modification methods of biochar

AbstractIn this reported work, lotus leaves‐derived biochar (LBC) was modified using various chemical methods. LBC prepared by different modification methods was used as the carrier for the development of low‐temperature selective catalytic reduction (SCR) catalysts. A comparative study of low‐temperature SCR manganese catalysts based on LBC chemically modified using NaOH, HNO3 and hexadecylcetyltrimethylammonium bromide (CTAB) was performed, revealing different deNOx performance of these catalysts. For the supported catalysts, the 25%Mn/LBC‐OH catalyst appeared to be optimum since it exhibited over 95% NOx conversion at 225 °C with a space velocity of 37 500 h−1. The microstructure, phase composition, redox properties and surface acidity were determined using field emission scanning electron microscopy, Brunauer–Emmett–Teller surface area, X‐ray diffraction, H2‐temperature‐programmed reduction, NH3‐temperature‐programmed desorption, and so forth. The results showed that the excellent SCR performance of 25%Mn/LBC‐OH was closely related to its abundant high valence Mn, suitable surface acidity and high redox capability. More importantly, highly dispersed MnOx easily formed on the surface of the LBC‐OH support, which was the key factor in the excellent catalytic activity of 25%Mn/LBC‐OH catalyst. Furthermore, the highly dispersed 25%Mn/LBC‐OH catalyst also exhibited improved tolerance to SO2 and H2O, making this catalyst a good candidate for reducing the NOx emission from coal‐fired power plants. © 2022 Society of Chemical Industry (SCI).

Chemoselective Oxyfunctionalization of Functionalized Benzylic Compounds with a Manganese Catalyst.

Whilst allowing for easy access to synthetically versatile motifs and for modification of bioactive molecules, the chemoselective benzylic oxidation reactions of functionalized alkyl arenes remain challenging. Reported in this study is a new non‐heme Mn catalyst stabilized by a bipiperidine‐based tetradentate ligand, which enables methylene oxidation of benzylic compounds by H2O2, showing high activity and excellent chemoselectivity under mild conditions. The protocol tolerates an unprecedentedly wide range of functional groups, including carboxylic acid and derivatives, ketone, cyano, azide, acetate, sulfonate, alkyne, amino acid, and amine units, thus providing a low‐cost, more sustainable and robust pathway for the facile synthesis of ketones, increase of complexity of organic molecules, and late‐stage modification of drugs.

Chemoselective Oxyfunctionalization of Functionalized Benzylic Compounds with a Manganese Catalyst

AbstractWhilst allowing for easy access to synthetically versatile motifs and for modification of bioactive molecules, the chemoselective benzylic oxidation reactions of functionalized alkyl arenes remain challenging. Reported in this study is a new non‐heme Mn catalyst stabilized by a bipiperidine‐based tetradentate ligand, which enables methylene oxidation of benzylic compounds by H2O2, showing high activity and excellent chemoselectivity under mild conditions. The protocol tolerates an unprecedentedly wide range of functional groups, including carboxylic acid and derivatives, ketone, cyano, azide, acetate, sulfonate, alkyne, amino acid, and amine units, thus providing a low‐cost, more sustainable and robust pathway for the facile synthesis of ketones, increase of complexity of organic molecules, and late‐stage modification of drugs.

Effect of Manganese Catalysts on the Performance of Anodes in Direct Carbon Fuel Cells

Effect of Manganese Catalysts on the Performance of Anodes in Direct Carbon Fuel Cells

Heterogenized manganese catalyst for C-, and N-alkylation of ketones and amines with alcohols by pyrolysis of molecularly defined complexes

Series of organic transformations are known to be catalyzed by molecularly well-defined homogeneous catalysts, however, it is difficult to recycle. Meanwhile, heterogeneous catalysts are required in many industrial processes due to their stability, and recyclability, but it is challenging to control on a molecular level. Herein, we set out the conversion of homogenous manganese complex into heterogeneous manganese-based catalyst via pyrolyzing the pre-formed crystalline polymer. The catalyst thus produced are then utilized for C–C/C–N bond-forming reactions, such as alkylation of ketones and/or amines, utilizing primary alcohols as an alkylating agent, under nearly mild conditions liberating water as the sole by-product.

Dehydrogenative and Redox-Neutral N-Heterocyclization of Aminoalcohols Catalyzed by Manganese Pincer Complexes

A new manganese catalyzed heterocyclization of aminoalcohols has been accomplished. A wide range of heterocycles were synthesized, including 1,2,3,4-tetrahydroquinolines, dihydroquinolinones, and 2,3,4,5-tetrahydro-1H-benzo[b]azepines. The reaction is performed under mild reaction conditions using air and moisture stable manganese catalysts. The desired heterocycles were obtained in good to excellent yields.

A SHORT REVIEW ON POLYVINYLPYRIDINE AND MANGANESE BASED COMPLEXES AS EFFICIENT CATALYSTS IN ORGANIC SYNTHESIS

Manganese and polyvinylpyridine-based complexes have been shown to be effective catalysts for many catalytic reactions. These catalysts carry out oxidation with very high efficiency, while activating the C-H groups and easily eliminating their internal reactivity. Although many manganese and polyvinylpyridine-based catalysts have significant activity, their application, as well as attempts to increase their synthetic potential, have not yet been developed. To this end, we reviewed studies on manganese and polyvinylpyridine-based catalysts to increase their application in many chemical reactions, such as the oxidation of n-alkanes, alcohols, and olefins, and hope that our brief review will lead to the development of new organic synthesis of Mn/polyvinylpyridine-based catalysts. Keywords: Poly-4-vinylpyridine, Mn(II) based catalysts, oxidation, organic synthesis

Hydration of Nitriles Enabled by PNP−manganese Pincer Catalyst

AbstractA general and practical methodology for the hydration of nitriles to primary amides enabled by manganese catalyst is presented. The described protocol shows broad substrate scope with good functional group tolerance, including a wide range of (hetero)aromatic and aliphatic nitriles, thus afforded the corresponding amides in good to excellent isolated yields under mild conditions. Preliminary mechanistic studies indicated that metal‐ligand cooperation (MLC) mode was involved in this catalytic process.

Assembly of sphere-structured MnO2 for total oxidation of propane: Structure-activity relationship and reaction mechanism determination

Through morphology control and structure construction of manganese catalyst to improve the conversion of VOCs is still a significant challenge in the field of environmental catalysis. Herein, secondary sphere structured δ-type manganese oxide (MnO2-SS) was synthesized via a simple room temperature two-step method. Compared with other sphere-type MnO2 samples, MnO2-SS exhibited a higher propane oxidation activity (T90 = 238 ℃), turnover frequency (14.54 × 10−7 s−1 at 240 ℃), and stability in H2O, NO2, and CO atmospheres. Experimental results indicated that MnO2-SS exhibited an ultrahigh specific surface area, a high surface concentration of active Mn4+ species and superior surface oxygen mobility. In-situ DRIFTs revealed that active oxygen species exhibit a key role in formation and dissociation of intermediate carboxylates. Electron paramagnetic resonance, O K-edge results and density functional theory calculation revealed that numerous oxygen vacancies existed on MnO2-SS. These vacancies can facilitate adsorption and activation of O2 to generate active reactive oxygen species, which lead to superior propane and intermediate carboxylates oxidation activity. This work provides new strategy to enhance the surface oxygen activity of manganese oxide.

Photoactive Fe Catalyst for Light-Triggered Alkyd Paint Curing.

Herein, we show that the photoactive complexes [(Cp)Fe(arene)]+ (Cp = cyclopentadienyl; arene = C6H6, C6H5Me) act as latent catalysts that allow for photochemical control over the onset of alkyd paint curing, without the need for antiskinning agents such as the volatile 2-butanone oxime normally used to prevent curing during paint storage. The highly soluble neutral complexes [(Cp)Fe(Ch)] and [(Cp)Fe(Ch′)] (Ch = cyclohexadienyl, Ch′ = methylcyclohexadienyl) readily convert to the photoactive complexes [(Cp)Fe(arene)]+ upon oxidation in alkyd, allowing the latter to be dosed in a wide range of concentrations. Infrared and Raman studies show similar spectral changes of the alkyd paint matrix as have been observed in alkyd curing mediated by well-known, industrially applied cobalt- and manganese-based catalyst Co(neodecanoate)2 and [(Me3TACN)2Mn2(μ-OOCR)3](OOCR). The [(Cp)Fe(Ch)]/[(Cp)Fe(arene)]+ system performs equally well as these cobalt- and manganese-based catalysts in terms of drying time and outperform the manganese catalyst by showing a hardness development (increase) similar to that of the cobalt-based catalyst. Based on electron paramagnetic resonance and light–activity studies, we propose that photolysis of [(Cp)Fe(arene)]+ generates short-lived active FeII species, explaining the desired latency. The [(Cp)Fe(Ch)]/[(Cp)Fe(arene)]+ alkyd curing systems presented herein are unique examples of intrinsically latent paint curing catalysts that (1) are based on an abundant and harmless transition metal (Fe), (2) do not require any antiskinning agents, and (3) show favorable performance in terms of drying times and hardness development.

Photoactive Metal Carbonyl Complexes Bearing N-Heterocyclic Carbene Ligands: Synthesis, Characterization, and Viability as Photoredox Catalysts.

This report details the synthesis and characterization of a small family of previously unreported, structurally related chromium, molybdenum, tungsten, manganese, and iron complexes bearing N-heterocyclic carbene and carbonyl supporting ligands. These complexes have the general form [ML(CO)3X] or [ML(CO)3], where X = CO or Br and L = 1-phenyl-3-(2-pyridyl)imidazolin-2-ylidene. Where possible, the solid-state, spectroscopic, electrochemical, and photophysical properties of these molecules were studied using a combination of experiment and theory. Photophysical studies reveal that decarbonylation occurs when these complexes are exposed to ultraviolet light, with the CO ligand being replaced with a labile acetonitrile solvent molecule. To obtain insights into the potential utility, scope, and applications of these complexes in visible-light-mediated photoredox catalysis, their capacity to facilitate a range of photoinduced reactions via the reductive or oxidative functionalization of organic molecules was investigated. These chromium, molybdenum, and manganese catalysts efficiently facilitated atom-transfer radical addition processes. In light of their photolability, these types of catalysts may potentially allow for the development of photoinduced reactions involving less conventional inner-sphere electron-transfer pathways.

Hydrogenation of Esters by Manganese Catalysts

AbstractThe hydrogenation of esters catalyzed by a manganese complex of phosphine‐aminopyridine ligand was developed. Using this protocol, a variety of (hetero)aromatic and aliphatic carboxylates including biomass‐derived esters and lactones were hydrogenated to primary alcohols with 63–98% yields. The manganese catalyst was found to be active for the hydrogenation of methyl benzoate, providing benzyl alcohol with turnover numbers (TON) as high as 45,000. Investigation of catalyst intermediates indicated that the amido manganese complex was the active catalyst species for the reaction.magnified image

Porous organic polymer-supported manganese catalysts with tunable wettability for efficient oxidation of secondary alcohols

Porous organic polymers (POPs) feature high surface areas, tunable components, and designable hierarchical pores, thus showing versatile applications including catalysis, separation, gas storage and so on. However, the inherently hydrophobic property may be unfavorable for the catalytic reaction that involves hydrophilic reactants. By using the hydrophilic principle of the amide bond, R-NH-CO-R can be constructed in the porous frameworks to regulate the wettability. Herein, we report the construction of an amphiphilic and hierarchical porous Mn-N4 catalyst via the solvothermal copolymerization, in which N,N-methylenebisacrylamide is used as a hydrophilic monomer. This POP-based manganese catalyst can effectively promote the oxidation of secondary alcohol to produce the ketone using aqueous hydrogen peroxide as the oxidant under mild conditions. Note that this amphiphilic catalyst displays high catalytic activity as its homogeneous counterpart in the selective oxidation of alcohols. The present work has provided a successful approach for improving the catalytic activity by tuning the wettability of POP-based heterogeneous catalysts.

Immortal Ring-Opening Copolymerization of Epoxide and Isocyanate Using a Commercial Manganese Catalyst

Immortal polymerization is a unique strategy for ring-opening copolymerizations (ROCOP) with epoxide monomers. In conjunction with various chain transfer agents (CTAs), the first immortal ROCOP of a typical epoxide (propylene oxide, PO) and isocyanate (p-tosyl isocyanate, TSI) using a commercial manganese catalyst is reported. In addition to precise molecular-weight control, this approach afforded novel polyurethane (PU) with unprecedented functionality, topology, and pinpoint sequence with secondary carbamyl linkage. In addition, a block copolymer of poly(lactic acid) (PLA) with PU was synthesized via a sequential addition strategy, which offered an attractive access to expanding the scope of copolymers derived from aliphatic polyesters.

Enhanced photocatalytic oxidation of reactive dye using manganese catalyst complex

In this work, the treatment efficiency of advanced oxidation processes H2O2/UV enhanced by the addition of a manganese catalyst complex (MnTACN) was investigated on a model dye solution and a real dye-house effluent. The experimental results were evaluated in terms of absorbance (A) and total organic carbon (TOC) reduction. The major degradation products of the model dye solution were identified by high resolution gas chromatography/mass spectrometry analyses. In addition, the toxicity of the final reaction solution after H2O2/UV/MnTACN treatment to Vibrio fischeri bacteria was determined. The results showed that the addition of the H2O2/UV/MnTACN system at different concentrations of the catalyst solution increased the decolourisation rate compared to H2O2/UV for both the model dye solution and real dye-house effluent.

A Novel Method for Rapid Mineralization of Azithromycin Via Manganese Catalysts Modified with O-Donor Ligands in Hydrogen Peroxide Oxidation Process

A Novel Method for Rapid Mineralization of Azithromycin Via Manganese Catalysts Modified with O-Donor Ligands in Hydrogen Peroxide Oxidation Process

Heterogenized Manganese Catalyst for C-, and N-Alkylation of Ketones and Amines with Alcohols by Pyrolysis of Molecularly Defined Complexes

Heterogenized Manganese Catalyst for C-, and N-Alkylation of Ketones and Amines with Alcohols by Pyrolysis of Molecularly Defined Complexes

Immobilizing a homogeneous manganese catalyst into MOF pores for α-alkylation of methylene ketones with alcohols.

Herein, for the first time, a metal-organic framework (MOF) is reported as a catalyst for α-alkylation of ketones with alcohols. Using an encapsulation strategy via nano-confinement of a homogeneous Mn-phenanthroline complex into MOF pores, functionalized branched ketones were selectively produced. Mechanistic investigations and deuterium labelling experiments validated the utilization of the borrowing hydrogen strategy. The formation of extra Lewis acid sites, defects, and pore enhancement during catalysis helped in achieving higher activity and selectivity.

Decarboxylative oxygenation of carboxylic acids with O2via a non-heme manganese catalyst

Reported here is a new protocol for the decarboxylative oxygenation of carboxylic acids using a non-heme manganese catalyst under blue light irradiation with O2 as the sole oxidant.