Oxidation Of Cyclohexanone Research Articles

Oxidative Cleavage of C−C Bonds in Non‐aromatic Oxygenates with Molecular Oxygen for Synthesis of Carboxylic Acids

AbstractOxidative carbon‐carbon cleavage reactions of non‐aromatic oxygenates such as vicinal diols are reviewed. In comparison with aromatic oxygenates where the benzyl positions are easily oxidized, non‐aromatic alcohols are difficult to be oxidized. The use of excess base in combination with metal catalysts is a typical approach, and the oxidations of 1,2‐cyclohexanediol and dihydroxylated derivatives of oleic acid have been reported with good yields of (di)carboxylate. Oxidation under acidic conditions typically uses vanadium as a key component of catalyst. Vanadium alone is active in oxidation of hydroxyketones and not effective in oxidation of saturated alcohols and polyols. Oxidation of sugars to formic acid is catalyzed by vanadium. For the oxidation of vicinal diols, the combination of platinum and vanadium is effective. There are some recently‐discovered systems for carbon‐carbon dissociation reactions of 1,2‐difunctionalized compounds, such as 2‐methoxycyclohexanone oxidation to adipic acid with polyoxometalate catalysts. On the other hand, the progress of research in the oxidation of cyclohexanone to adipic acid, which is an important industrial process, is less rapid, and we commented on the situation.

Selective Oxidation of Cyclohexanone to Adipic Acid Using Molecular Oxygen in the Presence of Alkyl Nitrites and Transition Metals as Catalysts.

This paper presents a not previously reported catalytic system consisting of transition metals Co2+ and Mn2+ and alkyl nitrites R-ONO for the oxidation of cyclohexanone with oxygen to adipic acid. The influence of type and amount of catalyst, temperature, time, and type of raw material on conversion and product composition were determined. In addition, the oxidation of selected cyclic ketones such as cyclopentanone, cyclohexanone, cyclooctanone, cyclododecanone, 2-methylcyclohexanone, 3-methylcyclohexanone, and 4-methylcyclohexanone in acetic acid as solvent was performed. The results showed that R-ONO systems, under established reaction conditions, form NO·radicals, which oxidize to NO2 under a strong oxidization reaction environment. The Co2+/Mn2+/NO2 system was shown to be highly active in the oxidation of cyclic ketones with oxygen.

Cage-like Cu5Cs4-Phenylsilsesquioxanes: Synthesis, Supramolecular Structures, and Catalytic Activity.

A small family of nonanuclear Cu5Cs4-based phenylsilsesquioxanes 1-2 were prepared by a convenient self-assembly approach and characterized by X-ray diffraction studies. The compounds 1 and 2 show some unprecedented structural features such as the presence of a [Ph14Si14O28]14- silsesquioxane ligand and a CuII5CsI4 nuclearity in which the metal cations occupy unusual positions within the cluster. Copper ions are "wrapped" into a silsesquioxane matrix, while cesium ions are located in external positions. This resulted in cesium-involved aggregation of coordination polymer structures. Both compounds 1 and 2 realize specific metallocene (cesium-phenyl) linkage between neighboring cages. Compound 2 is evaluated as a catalyst in the Baeyer-Villiger (B-V) oxidation of cyclohexanone and tandem cyclohexane oxidation/B-V oxidation of cyclohexanone with m-chloroperoxybenzoic acid (mCPBA) as an oxidant, in an aqueous acetonitrile medium, and HNO3 as the promoter. A quantitative yield of ε-caprolactone was achieved under conventional heating at 50 °C for 4 h or MW irradiation for 30 min (for cyclohexanone as substrate); 17 and 19% yields of lactone upon MW irradiation at 80 °C for 30 min and heating at 50 °C for 4 h, respectively (for cyclohexane as a substrate), were achieved. Complex 2 was evaluated as a catalyst for the oxidation of alkanes to alkyl hydroperoxides and alcohols to ketones with peroxides at 60 °C in acetonitrile. The maximum yield of cyclohexane oxidation products was 30%. Complex 2 exhibits high activity in the oxidation of alcohols.

Amino-anchored sulfonic acid-functionalized heteropolyacid ionic liquid: A highly selective and recyclable catalyst for the Baeyer-Villiger oxidation of cyclohexanone

A novel amino-anchored sulfonic acid functional heteropolyacid ionic liquid ([NHSO]3PW12O40) was designed, synthesized and used as a catalyst in the Baeyer-Villiger (BV) oxidation of cyclohexanone to synthetic ε-caprolactone (ε-CL). The catalyst was well characterized by FT-IR, XRD, 1H NMR, XPS, TG-DTA and SEM analysis methods, which showed that the tungsten phosphate anion (PW12O403−) was successfully modified from the sulphonate-functionalised IL precursor NHSO and formed a new hydrogen bond between the introduced –NH2 group and PW12O403−. The combined effect of ionic bonds and hydrogen bonds contributed to the good stability of the catalyst. Catalyst activity evaluation experiments confirmed that [NHSO]3PW12O40 exhibited superior performances such as a cyclohexanone conversion of 86% and ε-CL yield and selectivity of 82% and 95%, respectively. Furthermore, [NHSO]3PW12O40 could be recovered by simple treatment and the activity of the catalyst did not decrease significantly after five replicae experiments. In addition, the reaction kinetics and mechanism of the catalyst were investigated and a simple validation was given in conjunction with the bond energy changes of the catalyst during the reaction. The innovative of the green, stable and high-performance functionalised heteropolyacid IL catalyst provides a new solution for the efficient production of ε-CL.

A highly efficient bifunctional copper catalyst for Baeyer-Villiger oxidation of cyclohexanone: Two different active centers and the reaction path investigation

Polycaprolactone is a significant alternative to nondegradable plastic, and the synthesis of its monomer ε-caprolactone (ε-CL) has obtained increasing attention. Here, one kind of Cu-SiO2 bifunctional catalyst with highly dispersed copper species and various metal valences was developed and applied in Baeyer − Villiger (B-V) oxidation for cyclohexanone (Cy=O) to produce ε-CL with O2/benzaldehyde. The Lewis acidity and the different valence of the copper species could be adjusted by two simple post-treatment methods. The optimal Cu-SiO2-60-1.5 exhibits > 99 % conversion of Cy=O and > 99 % selectivity to ε-CL with high efficiency of BEA. The enhancement primarily originates from the synergism of Cu2+, Cu+, and the Lewis acidity of the catalysts. In addition, the possible mechanisms and realistic reaction path were proposed and verified by combing the characterization and DFT calculations. It clarifies the not well-understood reaction mechanism in B-V oxidation of Cy=O. And it reveals that the formation of the Ph-CO3H intermediate is rate-limiting step, and it is beneficial for the vital “Criegee” intermediates formation thanks to its lower activation energy. This work provides a promising strategy for designing suitable oxidative catalysts and clarifies realistic reaction path of B-V oxidation of Cy=O, which could improve the development of degradable plastics.

Effect of Sn and Zr Content in ZrAl- and SnAl-BEA Hierarchical Zeolites on Their Acidic and Catalytic Properties in the Process of Cyclohexanone Oxidation with Hydrogen Peroxide

Effect of Sn and Zr Content in ZrAl- and SnAl-BEA Hierarchical Zeolites on Their Acidic and Catalytic Properties in the Process of Cyclohexanone Oxidation with Hydrogen Peroxide

Highly enhanced direct catalytic oxidation of cyclohexane to adipic acid with molecular oxygen: Dynamic collaboration between zeolite channel micro-environment and Au clusters

Adipic acid is a valuable chemical used to product Nylon-66, and one of the greenest ways to synthesize it is catalyzing the oxidation of cyclohexane by molecular oxygen in the absence of any other chemicals. However, it is challenging to convert cyclohexane effectively with high selectivity to adipic acid using the available catalysts. In response to the dilemma of achieving satisfactory conversion and selectivity at the same time, a remarkable Au@NaX catalyst is proposed using an improved in-situ crystallization method that exhibits Au clusters surrounded by X-zeolite channels. A 29.5% conversion of cyclohexane and an 85.6% selectivity to adipic acid can be obtained in a one-pot oxidation of cyclohexane at 140 °C, 20 bar O2, far exceeding most published results. Since determined by detailed characterizations and DFT calculations, the effective dynamic collaboration between Au clusters and zeolite inner micro-environment is the decisive role for superior catalytic performance. Specifically, the surrounding zeolite channel encourages the adsorption and activation of cyclohexane over the confined Au clusters, resulting in an unprecedented activity. The continuous oxidation of cyclohexanol and cyclohexanone to adipic acid is also vulnerable on the enclosed Au clusters, and the subsequent adipic acid can be further stabilized as a result of the strong interaction of –COOH with Na± in zeolite channels surrounding enclosed Au clusters. It prevents AA from poisoning active sites and generates a higher selectivity for the desired adipic acid. Our study highlighted the critical significance of the dynamic interaction between metal clusters and the zeolite channel microenvironment. It would shed light on the further high-performance catalysts designs for selective oxidation.

Enhanced Photoinduced Baeyer–Villiger Oxidation of Ketones by Introducing Trinuclear Ruthenium Clusters into Polyoxometalate-Based Metal–Organic Frameworks

The development of solar-driven organic synthesis processes as an alternative to conventional thermo-catalytic technologies is of great research significance in academia and industry. Herein, we looked into the photoinduced Baeyer–Villiger oxidation of cyclohexanone based on the Mukaiyama method for the first time. We fabricated a crystalline polyoxometalate-based metal–organic framework photocatalyst, CR-SiW12, which represents the first example of trinuclear ruthenium clusters involved in the construction of polyoxometalate-based metal–organic frameworks. The cyclohexanone was efficiently converted to ε-caprolactone under visible light (>400 nm) irradiation with CR-SiW12 as the catalyst, with a reaction turnover number and turnover frequency recorded as 941 and 274.5 h–1, respectively, and the apparent quantum yield at 465 nm was measured to be 8.4%. Moreover, CR-SiW12 exhibited high structural stability and reaction reusability where reaction yield remained high at 91.3% after five consecutive reaction cycles. This work offers a promising strategy for accomplishing Baeyer–Villiger oxidation reactions under green conditions.

Isomorphous incorporation of tin ions into extra-large pore framework with high-stannum content as efficient Lewis acid catalyst

Germanium-rich *CTH zeolite without organic molecules located inside pore channels experienced only partial structural collapse and subsequently repaired to high-silica structure analogous to the original topology in a short time. The surprise acid-hydrolysis process has caused a large amount of framework Ge ions were removed, giving rise to abundant hydroxyl nests. Benefiting from the unexpected variation of framework structure and chemical composition, stannosilicates Sn-*CTH with extra-large pores and various Sn loadings (Si/Sn molar ratio in the range of 30-∞) were post-prepared depending on the reaction between the added (NH4)2SnCl6 species and the formed silanol groups in the hydroxyl nests. The resultant Sn-*CTH zeolites were able to release significantly the diffusion limitations encountered by the bulky substrates and oxidants, exhibiting promising activities to catalyze the Baeyer-Villiger (B-V) oxidation of ketones with single oxidant either hydrogen peroxide (H2O2) or large-sized tert-butyl hydroperoxide (TBHP). Especially, high ε-caprolactone product selectivity was also obtained in the B-V oxidation of cyclohexanone using H2O2 oxidant through reducing the H2O2/cyclohexanone molar ratio as well as controlling appropriate reaction time, which was more efficient than the traditional Sn-Beta-F catalyst.

The Baeyer–Villiger Oxidation of Cycloketones Using Hydrogen Peroxide as an Oxidant

Baeyer–Villiger oxidation can synthesize a series of esters or lactones that have essential application value but are difficult to be synthesized by other methods. Cycloketones can be oxidized to lactones using molecular oxygen, peroxy acids, or hydrogen peroxide as an oxidant. Hydrogen peroxide is one of the environmental oxidants. Because of the weak oxidation ability of hydrogen peroxide, Bronsted acids and Lewis acids are used as catalysts to activate hydrogen peroxide or the carbonyl of ketones to increase the nucleophilic performance of hydrogen peroxide. The catalytic mechanisms of Bronsted acids and Lewis acids differ in the Baeyer–Villiger oxidation of cyclohexanone with an aqueous solution of hydrogen peroxide as an oxidant.

H3PMo12O40@MOF as a New Catalytic System for Cycloxexanone Oxidation to Adipic Acid

Keggin-type phosphomolibdic acid (H3PMo12O40, PMo12) encapsulated in the mesocages of chromium-based terephthalate metal–organic framework (MIL-101), was established to be an active and new green catalyst for the adipic acid (AA) synthesis via cyclohexanone (-One) oxidation in free solvent conditions and hydrogen peroxide as green oxidant. In this paper, we wish to report the synthesis of MIL-101 with different high loadings of the PMo12 nanocrystals incorporated within the large pores of MIL-101. Two and five POMs per large cavity can be incorporated into the matrix of MIL-101 respectively, xH3PMo12@ MIL101 with x=0, 2 and 5, they were characterized by several physic-chemical technics, then investigated in the reaction oxidation with 30 mmol –One at 90 ° C for 20h. A sequenced addition of 0.5ml of H2O2 (30%) was made every 30 min. The catalysts have shown good activity and the purity of AA was invistigeted by 1H and 13C NMR.

Identification of the reaction network for the synthesis of adipic acid using machine learning coupling with target factor analysis

AbstractThis study investigated the reaction network of the oxidation of cyclohexanone with nitric acid through machine learning (ML) model coupling with target factor analysis (TFA). Experiments for the synthesis of adipic acid (AA) were carefully designed and carried out in a microreactor system. An artificial neural network (ANN) model was applied and optimized by training on experimental data. To assess the established ANN model, a comparison between the predicted concentrations of the products and those calculated with the power law kinetic model was implemented. TFA was then performed on both the experimental data and the data simulated by ANN for identifying the candidate reactions and finding out the temperature boundaries. Based on the identification results of the reaction network, the kinetic characteristics of this oxidation process under various operational conditions were further researched through the incremental approach and simultaneous approach.

Oxidation of Cyclohexanone with Peracids-A Straight Path to the Synthesis of ε-Caprolactone Oligomers.

During Baeyer–Villiger (BV) oxidation of cyclohexanone with peracids, oligo(ε-caprolactone) (OCL) may be formed. In this work, a two-step one-pot method for the synthesis of OCL involving the BV oxidation of cyclohexanone with peracids and then oligomerization of the resulting ε-caprolactone has been developed. The process was carried out in two solvents: toluene and cyclohexane. Based on the studies, it was determined that the increased temperature (45–55 °C) and the longer reaction time (4 h) favor the formation of OCls. Among the tested peracids (perC8-C12), perC10 turned out to be the most effective oxidant. Moreover, the obtained oligomers were characterized by means of NMR, MS MALDI TOF, and TGA analyses, which made it possible to determine the structure of oligomers (length and terminal groups of the chains). Additionally, the oligomers obtained after the distillation of the reaction mixture were analyzed.

Preparation, characterization of mixed-valence antimony-tin phosphomolybdic polyoxometalates and application in the cyclohexanone oxidation in the presence of hydrogen peroxide

In this work, a series of polyoxometalates (POMs), as soluble salts of formula Sn1.5PMo12O40, SbPMo12O40 and H 3-x Sn x1 Sb x2 PMo 12 O 40 (x=2x 1 +3x 2 and x 1 , x 2 = 0–0.75) were synthesized using the cationic exchange method under stoichiometric conditions. They were characterized and tested in the oxidation of cyclohexanone using hydrogen peroxide in the absence of organic solvent, co-catalyst phase transfer compounds or surfactants. UV–Visible and X-ray photoelectron spectroscopic analyses showed a partially reduced state of POM with coexistence of the couples Mo(VI)/Mo(V), Sb(V)/Sb(III) and Sn(IV)/Sn(II), without affecting their structure, results confirmed by FT-IR and Raman spectroscopies. The reversible cyclic voltammetry analysis evidenced the valence change of the Mo species, Mo(VI)/Mo(V). The POMs are found to be active in the cyclohexanone oxidation reaction and among them the most efficient is H 0.75 Sb 0.75 PMo 12 O 40 with 49% of adipic acid yield.

Kinetically guided high‐yield and rapid production of ε‐caprolactone in a microreactor system

AbstractIndustrial production of ε‐caprolactone, the monomer of biodegradable polycaprolactone, consists of acetic acid peroxidation and the Baeyer–Villiger oxidation of cyclohexanone in semi‐batch reactors. The strong exothermic feature of the latter and ease of ε‐caprolactone hydrolysis significantly affects the production efficiency. Here, collective effects of kinetic studies and density functional theory (DFT) calculations reveal activation energy of the Baeyer–Villiger oxidation is higher than that of ε‐caprolactone hydrolysis and the hydrolysis barrier is controlled by hydrogen bond energy of the reaction medium. Then, we developed a microreactor system to intensify heat transfer thereby allowing safe and efficient production of ε‐caprolactone. A yield of 99.6% was achieved within minutes via consecutive two‐step reactions of peroxidation and the Baeyer–Villiger oxidation, as compared with state‐of‐the‐art yield of 96% in hours of industrial operation. The high selectivity is attributed to high reaction temperature allowed by the microreactor and DFT‐guided choice of solvent to mitigate the hydrolysis.

Influence of the Structure and Composition of H3–2xMnxPMo12O40 AND (NH4)3–2xMnxPMo12O40 Heteropolycompounds on their Catalytic Properties in the Process of Cyclohexanone Oxidation with Hydrogen Peroxide

Influence of the Structure and Composition of H3–2xMnxPMo12O40 AND (NH4)3–2xMnxPMo12O40 Heteropolycompounds on their Catalytic Properties in the Process of Cyclohexanone Oxidation with Hydrogen Peroxide

New Organic-Inorganic Hybrid Compounds Based on Sodium Peroxidomolybdates (VI) and Derivatives of Pyridine Acids: Structure Determination and Catalytic Properties.

Two organic-inorganic hybrids based on sodium peroxidomolybdates(VI) and 3,5-dicarboxylic pyridine acid (Na-35dcpa) or N-oxide isonicotinic acid (Na-isoO) have been synthesized and characterized. All compounds contain inorganic parts: a pentagonal bipyramid with molybdenum center, and an organic part containing 3,5-dicarboxylic pyridine acid or N-oxide isonicotinic acid moieties. The type of organic part used in the synthesis influences the crystal structure of obtained compounds. This aspect can be interesting for crystal engineering. Crystal structures were determined using powder X-ray diffraction or single crystal diffraction for compounds Na-35dcpa and Na-isoO, respectively. Elemental analysis was used to check the purity of the obtained compounds, while X-ray Powder Diffraction (XRPD) vs. temp. was applied to verify their stability. Moreover, all the compounds were examined by Infrared (IR) spectroscopy. Their catalytic activity was tested in the Baeyer–Villiger (BV) oxidation of cyclohexanone to ε-caprolactone in the oxygen-aldehyde system. The highest catalytic activity in the BV oxidation was observed for Na-35dcpa. The compounds were also tested for biological activity on human normal cells (fibroblasts) and colon cancer cell lines (HT-29, LoVo, SW 620, HCT 116). All compounds were cytotoxic against tumor cells with metastatic characteristics, which makes them interesting and promising candidates for further investigations of specific anticancer mechanisms.

Electrocatalytic synthesis of adipic acid coupled with H2 production enhanced by a ligand modification strategy

Adipic acid is an important building block of polymers, and is commercially produced by thermo-catalytic oxidation of ketone-alcohol oil (a mixture of cyclohexanol and cyclohexanone). However, this process heavily relies on the use of corrosive nitric acid while releases nitrous oxide as a potent greenhouse gas. Herein, we report an electrocatalytic strategy for the oxidation of cyclohexanone to adipic acid coupled with H2 production over a nickel hydroxide (Ni(OH)2) catalyst modified with sodium dodecyl sulfonate (SDS). The intercalated SDS facilitates the enrichment of immiscible cyclohexanone in aqueous medium, thus achieving 3.6-fold greater productivity of adipic acid and higher faradaic efficiency (FE) compared with pure Ni(OH)2 (93% versus 56%). This strategy is demonstrated effective for a variety of immiscible aldehydes and ketones in aqueous solution. Furthermore, we design a realistic two-electrode flow electrolyzer for electrooxidation of cyclohexanone coupling with H2 production, attaining adipic acid productivity of 4.7 mmol coupled with H2 productivity of 8.0 L at 0.8 A (corresponding to 30 mA cm−2) in 24 h.

Comparative Physicochemical and Catalytic Study of Nanocrystalline Mg-Al Hydrotalcites Precipitated with Inorganic and Organic Bases.

Synthetic Mg-Al hydrotalcites (HT) are environmentally friendly solid bases frequently applied as catalysts in base catalyzed reactions. The most common synthesis method, using NaOH as precipitant, is problematized by the possibility of introducing undesired Na contamination. Alkali-free synthesis is usually performed with NH3aq, a precipitant which is less efficient in incorporation of Mg into HT lattice. In the present work, organic bases, tetrabutylammonium hydroxide and choline hydroxide, were successfully employed as precipitating agents in a new alkali-free route of Mg-Al HT synthesis. HT solids were also obtained with inorganic bases, NH3aq and NaOH. Characterization with X-ray diffraction, elemental analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy and thermogravimetry/differential scanning calorimetry, confirmed the formation of nanocrystalline HT compounds with all employed bases. HT prepared with NH3aq exhibited an Mg deficit, which was detrimental to the catalytic activity in base catalyzed reactions. The effect was attributed to the tendency of Mg2+ to form ammine complexes, a conclusion supported by quantum mechanical calculations. HT prepared with NaOH showed the highest crystallinity, which was unfavorable for catalytic application. The addition of starch to the synthesis medium provided a means by which to diminish the crystal size of all HT precipitates. Catalytic tests of the Baeyer–Villiger oxidation of cyclohexanone demonstrated that the highest yields of ε-caprolactone were obtained with fine-crystalline HT catalysts prepared with organic bases in the presence of a starch template.

Synthesis of Metal Xanthene‐Bridged Bis‐corroles and their Catalytic Activity in Aerobic Baeyer‐Villiger Oxidation Reaction

AbstractThe metal (M=Co, Cu, Mn, Sn, Fe) xanthene‐bridged bis‐corroles (M2XBC) were synthesized and used for catalyzing aerobic Baeyer‐Villiger (B‐V) oxidation of cyclic ketones to corresponding lactones. It turns out iron (IV) bis‐corrole complex (Fe2XBC) exhibited excellent activity and selectivity towards the B‐V oxidation of various cyclic ketones at very low catalyst loading. The yield of ϵ‐caprolactone could reach 98% with only 0.005 mol% catalyst. The turnover number (TON) of the Fe2XBC catalyst could even be up to 17400 in a gram‐scale oxidation of cyclohexanone, showing the promising for industrial usage. Moreover, the existences of benzoyl radical and benzoylperoxy radical in the reaction were proved by ESI‐HRMS spectra and electron paramagnetic resonance (EPR) spectra. A plausible radical mechanism for the metal bis‐corrole catalyzed aerobic B‐V oxidation of cyclohexanone in the presence benzaldehyde additive was proposed.