Oxidation Of Cyclohexanone Research Articles

Mechanistic Study of Ruthenium(III) Catalyzed Oxidation of Cyclohexanone by Acidic Bromate

In this work, kinetics and mechanism of Ru(III) catalyzed oxidation of cyclohexanone by acidified solution of potassium bromate has been studied. Present study employ mercuric acetate Hg (OAc)2 as a scavenger for Br¯ ion to prevent parallel oxidation by bromine. The kinetics and mechanism have also been studied in the temperature range of 30°C - 45°C. The reaction exhibits first order kinetics with respect to Ru (III), while zero order kinetics with respect to KBrO3 and HClO4. The influence of Hg(OAc)2 and ionic strength on the rate of reaction was found to be insignificant. Positive effect in the reaction mixture was also observed upon addition of chloride ion; while as the negative effect was revealed with acetic acid. A suitable mechanism in conformity with the kinetic observations has been proposed and the rate law is derived on the basis of obtained data. The various activation parameters such as energy of activation (ΔE*), Arrhenius factor (A), entropy of activation (ΔS*) were calculated from the rate measurements at 30°C, 35°C - 40°C and 45°C.

Clean Adipic Acid Synthesis from Liquid-Phase Oxidation of Cyclohexanone and Cyclohexanol Using (NH4)xAyPMo12O40 (A: Sb, Sn, Bi) Mixed Heteropolysalts and Hydrogen Peroxide in Free Solvent

Clean synthesis of adipic acid (AA) from oxidation of cyclohexanone, cyclohexanol or mixture cyclohexanol/cyclohexanone, was carried out at 90 °C, in the presence of hydrogen peroxide (30%) in free solvent, using Keggin-type polyoxometalates, (NH4)xAyPMo12O40 (An+=Sb3+, Bi3+ or Sn2+), as catalysts. HPLC analysis of reaction mixture showed the formation of adipic, succinic and glutaric acids and unidentified products. The salts were found to be effective for AA synthesis. Whatever the composition of the catalyst, the alcohol oxidation favors the formation of the unidentified products, unlike the ketone oxidation which favors that of the adipic acid. (NH4)0.5Sn1.25PMo12O40 led to the highest AA yield (56%) from cyclohexanone oxidation, after 20 h of reaction. In addition, 31P NMR analysis showed that it has conserved the Keggin structure contrary to others catalysts and that it can be used at least 3 times with reaction times of 20 h, without regeneration. From different catalytic tests and 31P NMR data, reaction pathways have been proposed. The active species could be peroxo-polyoxometalates.

Sn-Modified NaY Zeolite Catalysts Prepared by Post-Synthesis Methods for Baeyer–Villiger Oxidation

The Sn–NaY zeolite catalysts, Sn–NaY-gas and Sn–NaY-liq, were prepared by two-step post-synthesis methods, through hydrothermal dealumination and the post-incorporation of Sn species using chemical vapor deposition and impregnation separately. The Sn-ion incorporation and the physicochemical properties of the catalysts were characterized by various techniques. The amount of Sn species that were incorporated into the zeolite framework depended closely on the Sn introduction method. Sn–NaY-gas was found to have more Lewis-acid tetracoordinated Sn sites, which led to a better catalytic performance in the Baeyer–Villiger oxidation of cyclohexanone. The higher Sn loadings in the Sn–NaY-liq (3.4%) resulted in many inactive amorphous extra-framework Sn species, which also caused partial blockage of the zeolite pores and led to a loss in catalytic efficiency. Therefore, chemical vapor deposition could be used to form more active Lewis acidic Sn sites.

Draft Genome Sequence of Cyclohexylamine-Degrading Strain Acinetobacter sp. YT-02 Isolated.

Acinetobacter sp. YT-02, a Gram-negative bacterium isolated from the activated sludge from a sodium N-cyclohexylsulfamate production plant, has the ability to degrade cyclohexylamine. It was classified as a member of Acinetobacter sp., a Gram-negative bacterium, sharing a 16S rRNA gene sequence identity of 99% with Acinetobacter guangdongensis strain 1NM-4. It could degrade 10mmol/L cyclohexylamine within 22h. Based on the identified metabolite, the metabolic pathway of cyclohexylamine could be postulated as it was degraded via cyclohexanone. Draft genome sequence of this strain (2,993, 647bp of chromosome length) is presented here. We further identified the genes encoding the enzymes involved in cyclohexylamine oxidation to cyclohexanone and the subsequent downstream metabolic pathway of cyclohexanone oxidation. Strain YT-02 has the potentiality to be applied in the treatment of the pollutant cyclohexylamine, and it could also be treated as a research material to study the degradation mechanism of cyclohexylamine.

A new microporous oxyfluorinated titanium(IV) phosphate as an efficient heterogeneous catalyst for the selective oxidation of cyclohexanone

Designing a new porous nanomaterial for eco-friendly catalytic reactions is very challenging. Here, a new crystalline microporous oxyfluorinated titanium phosphate material (TIPO-1) has been synthesized under hydrothermal conditions in the absence of any structure directing agent. The triclinic crystalline phase with the unit cell parameters a=7.962Å, b=10.006Å, c=13.979Å, α=96.921°, β=95.851° and γ=93.760° has been indexed for TIPO-1 and it has been characterized through powder X-ray diffraction, nitrogen adsorption/desorption, XPS, FT-IR, 31P MAS NMR spectroscopy, UHR-TEM, FE-SEM and TGA/DTA analysis. The material exhibited excellent catalytic activity in liquid phase partial oxidation of cyclohexanone to adipic acid (up to 92% conversion) in the presence of aqueous H2O2 as oxidant together with value added side products like 1,6-hexandial and ε-caprolactone for reactions in different solvents. The material showed excellent recycling efficiency for six consecutive reaction cycles without any significant loss in catalytic activity.

Ionic liquid infiltrated within metal loaded zeolites for Baeyer–Villiger oxidation reaction under solvent-free condition

We demonstrate the infiltration of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) skeleton within robust Co metal loaded mesoporous zeolites viz. Co/ZSM-5 and/or Co/HY to prepare the ([BMIM]BF4@Co/ZSM-5) and/or ([BMIM]BF4@Co/HY) host–guest systems and characterized by various physico–chemical techniques. The catalytic activity of these catalysts was investigated in the liquid phase Baeyer–Villiger (BV) oxidation of cyclohexanone under solvent-free condition. Amongst them, [BMIM]BF4@Co/HY was found to be potential candidate by showing excellent performance with 54.88% conversion of cyclohexanone and 86.36% e-caprolactone selectivity with elevated TOF and TON values of 4312.43 h−1 and 25874.58, respectively. In addition to this, the host–guest system could be successfully recycled six times without significant loss of activity.

The multifunctional mesoporous Sn–Cu–Ti catalysts for the B–V oxidation of cyclohexanone by molecular oxygen

The multifunctional three-component mesoporous Sn–Cu–Ti samples were successfully prepared by a facile one-pot AcHE method and characterized by XRD, N2 sorption, ICP, FT-IR, UV–vis, SEM and TEM techniques, and their catalytic performances were carried out in the B–V oxidation of cyclohexanone by molecular oxygen. The results show that both tin and copper species can homogeneously incorporated in the crystalline framework of mesoporous anatase TiO2, where tin species as the active sites would increase the Lewis acidity and the oxidation of benzaldehyde as pro-oxygenic agent would be promoted by the introduction of little copper species resulting in the improving catalytic performance. The prepared 15Sn–3Cu–Ti catalyst shows higher yield of e-caprolactone than other catalysts and exhibits excellent catalytic stability even after repeated reaction for five times without any further treatment. The outstanding catalytic performance for Sn–Cu–Ti catalysts could offer a valuable reference for the industrial development of B–V oxidation of cyclohexanone.

Enhancing the Activity of a Dietzia sp. D5 Baeyer‐Villiger Monooxygenase towards Cyclohexanone by Saturation Mutagenesis

AbstractA recombinant Baeyer‐Villiger monooxygenase, BVMO4 from Dietzia sp. D5 has been previously reported. The enzyme exhibited good thermostability and was active with a wide range of cyclic ketone substrates but catalysed poorly the conversion of cyclohexanone to caprolactone. The present work focuses on protein engineering of BVMO4 to improve the conversion of cyclohexanone. Thus, a structural model of BVMO4 was generated and used in combination with literature information on substrate specificity of BVMOs to identify ‘hotspots’ whose mutation would influence substrate specificity. Site saturation mutagenesis was performed on 12 selected sites and 528 mutants were screened with expected coverage of about 98 %. About one‐fourth of the mutants screened exhibited more than 50 % increase in cyclohexanone oxidation activity. Compared to the wild type BVMO, the best mutants, Y499I, Y499F and Y499 L have shown about 12‐fold increase for caprolactone production.

Baeyer-Villiger oxidation of cyclohexanone with H2O2/acetonitrile over hydrotalcite-like catalysts: Effect of Mg/Al ratio on the ε-caprolactone yield

Phase-pure magnesium-aluminium hydrotalcite-like compounds with molar ratios of Mg/Al ranging from 1.93 to 6.63 were synthesized and characterized with ICP OES, XRD, BET, and Raman spectroscopy. The materials were used as catalysts in the Baeyer-Villiger oxidation of cyclohexanone to ε-caprolactone with H2O2/acetonitrile oxidizing system in mild conditions (70°C, atmospheric pressure). Initial catalysts activity increased with growing Mg content/basicity, but after completion of the catalytic run best ε-caprolactone yield was obtained for the catalyst with Mg/Al=5.62. Poorer than expected performance of the material richest in magnesium was attributed to the enhanced leaching of Mg in the mildly acidic reaction environment. The occurrence of the homogeneous catalytic reaction involving leached magnesium has been excluded. Recycling experiments show that leaching of Mg causes partial deactivation, but the catalysts can be easily regenerated and regain the initial performance.

Sn-Beta zeolite hydrothermally synthesized via interzeolite transformation as efficient Lewis acid catalyst

An innovative hydrothermal synthesis strategy of heteroatom-containing zeolite, in this case Sn-Beta, via interzeolite transformation is reported in present study. To the best of our knowledge, this prepared Sn-Beta zeolite possesses the highest isolated Sn contents (3.03wt% or Si/Sn molar ratio of 63) in comparison to other hydrothermally synthesized ones. The success of this synthesis strategy to Sn-Beta synthesized from MWW silica is mainly due to its nucleating and growing readily compared with those prepared from amorphous silica source. The introduction of Beta seeds and the structural similarity between the parent zeolite (MWW) and the targeted zeolite (*BEA) are found to be indispensable factors in the crystallization of Sn-Beta zeolite. The obtained Sn-Beta zeolites possess isolated tetrahedral Sn4+ in the framework and high hydrophobicity. Additionally, lowering the molar ratio of H2O2 to cyclohexanone and moderately reducing reaction time are proved to be effective methods to improve the selectivity of ε-caprolactone in the Baeyer–Villiger oxidation of cyclohexanone with H2O2 using Sn-Beta as Lewis catalyst. Thus, the prepared Sn-Beta zeolite demonstrated promising catalytic properties, especially for the desired products selectivity, in the Baeyer–Villiger oxidation of ketones as well as the isomerization–esterification reaction of dihydroxyacetone in ethanol, far outperforming the conventional Sn-Beta-F catalyst, which were attributed mainly to its high Sn content in the framework and excellent diffusion properties resulting from the relatively small crystal size.

Genome-wide identification and characterization of genes encoding cyclohexylamine degradation in a novel cyclohexylamine-degrading bacterial strain of Pseudomonas plecoglossicida NyZ12

The Gram-negative strain of Pseudomonas plecoglossicida NyZ12 isolated from soil has the ability to degrade cyclohexylamine (CHAM). The genes encoding CHAM degradation by gram-negative bacteria, however, have not been reported previously. In this study, ORFs predicted to encode CHAM degradation by NyZ12 were identified by bioinformatics analysis. Differential expression of the proposed ORFs was analyzed via RNA-seq and quantitative reverse transcription-PCR (qRT-PCR), using RNA extracted from NyZ12 cultured with or without CHAM addition. One CHAM-inducible ORF, RK21_02867 predicted to encode a cyclohexanone monooxygenase (ChnB) was disrupted, as were five ORFs, RK21_00425, RK21_02631, RK21_04207, RK21_04637 and RK21_05539, that had weak homology to the only known cyclohexylamine oxidase (CHAO encoded by chaA) found in Brevibacterium oxydans IH-35A. We also found that a tandem array of five ORFs (RK21_02866-02870) shared homology with those in an operon responsible for oxidation of cyclohexanone to adipic acid, although the ORFs in strain NyZ12 were arranged in a different order with previously found in cyclohexane, cyclohexanol or cyclohexanone degradation strains. The ORFs in this cluster were all up-regulated when CHAM was supplied as the sole carbon source. When one of these five genes, RK21_02867 encoding cyclohexanone (CHnone) monooxygenase, was knocked out, NyZ12 could not grow on CHAM, but it accumulated equimolar amounts of CHnone. Our results show that strain NyZ12 metabolized CHAM directly to CHnone which was then further metabolized to adipate. Despite clearly identifying genes encoding the steps for metabolism of CHAM metabolites, not every one of the putative chaAs was differentially expressed in the presence of CHAM and deletion of each one individually did not completely eliminate the capacity of NyZ12 to degrade CHAM, though it did reduce its growth in several instances. Our results suggest that there is genetic redundancy encoding the initial step in the oxidation of CHAM to CHnone in NyZ12 and that its CHAOs differ considerably from the ChaA, originally described in Brevibacterium oxydans IH-35A.

Engineering a lipase B from Candida antactica with efficient perhydrolysis performance by eliminating its hydrolase activity

A Ser105Ala mutant of the lipase B from Candida antarctica enables ‘perhydrolase-only’ reactions. At the example of the chemoenzymatic Baeyer-Villiger oxidation of cyclohexanone, we demonstrate that with this mutant selective oxidation can be achieved in deep eutectic solvent while essentially eliminating the undesired hydrolysis reaction of the product.

Role of Al3+ species in beta zeolites for Baeyer–Villiger oxidation of cyclic ketones by using H2O2 as an environmentally friendly oxidant

In this study, the Baeyer–Villiger (BV) oxidation of cyclic ketones to corresponding lactones using proton-type β-zeolite catalysts with various Al contents using an environmentally friendly oxidant (H2O2) was investigated. With respect to the selective oxidation of cyclobutanone to the corresponding γ-butyrolactone, the hydrolysis of which hardly proceeded under the reaction conditions employed, the conversion of cyclobutanone and H2O2 and yield of γ-butyrolactone increased with increasing Al content of up to 418μmol/g (Si/Al ratio of 39.0), followed by marginal decrease at Al contents greater than 418μmol/g. These trends were clearly correlated to the amount of Brønsted acid sites as estimated by the combination of temperature programmed desorption of NH3 (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR) measurements for adsorbed pyridine. These results strongly indicated that the Brønsted acid sites in β-zeolite catalysts serve as the active sites for the BV oxidation. On the other hand, for the BV oxidation of cyclohexanone to ε-caprolactone (the corresponding BV product), the selectivity of ε-caprolactone was maintained constant up to an Al content of 418μmol/g, but it gradually decreased at Al contents greater than 418μmol/g. An apparent correlation was observed between the amount of Lewis acid sites, attributed to the extra-framework Al species, and the trend of ε-caprolactone selectivity. These results suggested that the extra-framework Al species leads to the acceleration of the successive hydrolysis of ε-caprolactone.

Gaseous cyclohexanone catalytic oxidation by a self-assembled Pt/γ-Al2O3catalyst: process optimization, mechanistic study, and kinetic analysis

γ-Al2O3nanocatalysts with a Pt loading of 0.6–1.0% were prepared successfullyviaa self-assembly method to be used in the catalytic oxidation of cyclohexanone in a fixed-bed reactor.

Flexibility and lability of a phenyl ligand in hetero-organometallic 3d metal–Sn(iv) compounds and their catalytic activity in Baeyer–Villiger oxidation of cyclohexanone

The single compartmental Schiff base N,N'-ethylenebis(salicylaldimine) (H2L) and [SnPh2Cl2] were utilized to synthesize heterobimetallic 3d metal-Sn complexes, the CoIIISnIV compound [{SnPhCl2}(1κO2N2,2κO2-μ-L)(μ-OMe){CoPh}] (1), the NiIISnIV compound [{SnPh2Cl2}(1κO2N2,2κO2-μ-L)Ni] (2) and the CuIISnIV compound [{SnPh2Cl2}(1κO2N2,2κO2-μ-L)Cu] (3). Attempting to prepare the ethoxido bridged compound analogous to 1 (in ethanol) gives the phenylcobalt(iii) complex [Co(κO2N2)Ph(H2O)] (1A). Single crystal X-ray structure analyses reveal that 1 is derived from an intermetallic (Sn to Co) phenyl shift and that 1A is a transmetallated product; in compounds 2 and 3, the phenyl groups remain coordinated to SnIV but one of the π rings interacts with the 3d-metal. Thus, while systems 1 and 1A show the lability of the phenyl ligand, 2 and 3 reveal its flexible nature. Theoretical DFT calculations demonstrate that the conceivable Ph group shift occurs in the oxidized CoIII intermediate [{SnIVPh2Cl2}(κO2N2-μ-L){CoIII(MeO)}] (5) rather than in the corresponding CoII species [{SnIVPh2Cl2}(κO2N2-μ-L){CoII(MeOH)}] (4). Their catalytic studies in the Baeyer-Villiger oxidation of cyclohexanone into ε-caprolactone with two different oxidants reveal that the sacrificial aldehyde method (with dioxygen/benzaldehyde) is better than that with aqueous H2O2 (30%). The effects of various reaction parameters such as solvent, catalyst amount, temperature, time and heating method were studied allowing the achievement of yields up to 83% with 89% selectivity.

Influence of Hydrophilicity on the Snβ‐Catalyzed Baeyer–Villiger Oxidation of Cyclohexanone with Aqueous Hydrogen Peroxide

AbstractSnβ zeolites are amongst the most effective heterogeneous catalysts for the Baeyer–Villiger (BV) oxidation of ketones with aqueous hydrogen peroxide (H2O2). The high selectivity is rooted in the activation of the carbonyl substrate through interaction with the isolated SnIV sites. However, these sites are also accessible to other molecules in the reaction mixture (in particular the co‐solvent and product). In this contribution, we report the impact of competitive adsorption on the Snβ‐catalyzed BV oxidation of cyclohexanone with aqueous H2O2. We furthermore prepared a series of Snβ zeolites with varying amounts of framework silanols and quantified their hydrophilicities with water adsorption and IR experiments. By correlating the results with catalytic data, we show that Snβ zeolites with an intermediate hydrophilicity achieve the highest activity. Our adaptable post‐synthetic synthesis allows us to tune the material synthesis, resulting in enhanced activity compared with conventional hydrothermal Snβ.

Ordered mesoporous Sn–TiO2 catalysts via an evaporation induced self-assembly method for the Baeyer–Villiger oxidation of cyclohexanone by molecular oxygen

In order to improve the catalytic performance in the Baeyer–Villiger oxidation of cyclohexanone by molecular oxygen, ordered mesoporous Sn–TiO2 catalysts with high Lewis acidity were successfully designed and synthesized via a facile one-pot evaporation induced self-assembly method. Their physical and chemical properties were characterized by different techniques including XRD, N2 adsorption–desorption, UV–Vis spectra, ICP, Py-IR, SEM and TEM. The XRD, TEM and N2 adsorption–desorption results showed that the ordered mesoporous structure can be preserved after tin incorporation. The UV–Vis, SEM and Py-IR results indicated that tin species can be homogeneously tetrahedrally incorporated in the crystalline framework of mesoporous anatase TiO2 and create the Lewis acidity. The ordered mesoporous 15Sn–TiO2 catalyst showed highest catalytic performance where cyclohexanone conversion of 91.4 % and e-caprolactone selectivity of 93.2 %. Moreover, catalytic recycling tests demonstrated that the Sn–TiO2 catalysts exhibited high potential reusability.

Selectivity and Lifetime Effects in Zeolite‐Catalysed Baeyer–Villiger Oxidation Investigated in Batch and Continuous Flow

AbstractIn this manuscript, we investigate the kinetic, mechanistic and lifetime aspects of the Baeyer–Villiger oxidation of cyclohexanone with Sn‐β as catalyst and H2O2 as oxidant, with the aim of: 1) elucidating the overall reaction network, 2) closing the carbon balance, particularly at high levels of conversion, and 3) examining the intensification of this process in the continuous regime. The results presented herein conclusively demonstrate that this reaction is highly selective for the desired product (ϵ‐caprolactone) only below conversions of 60 %. Above this level of conversion, unavoidable hydrolysis of ϵ‐caprolactone to 6‐hydroxyhexanoic acid is observed, which consumes the desired product and leads to a reduction in catalytic activity through poisoning. By elucidating the reaction network and working under optimised conditions, we show the potential viability of this methodology to operate continuously over a 180 h period, both at high levels of productivity (324 g (cyclohexanone converted) cm−3 (reactor volume) kg−1 (catalyst) h−1) and selectivity (70 % at 60 % conversion). Over 5000 substrate turnovers were observed during this period, an order of magnitude higher than previously noted for this particular catalyst system.

New Hybrid Iron Phosphonate Material as an Efficient Catalyst for the Synthesis of Adipic Acid in Air and Water

A new organic–inorganic hybrid iron phosphonate material (FePO-1-2) has been synthesized hydrothermally using etidronic acid (1-hydroxyethylidene-1,1-diphosphonic acid) as an organophosphorus precursor. Under optimized reaction conditions the synthesis has been carried out hydrothermally for 3 days at 180 °C temperature at near neutral pH. The material has been characterized thoroughly by various techniques and its crystal structure has been indexed to a new orthorhombic phase with unit cell parameters of a = 10.995 A, b = 10.395 A, c = 11.793 A, and α = β = γ = 90°. The considerably good Brunauer–Emmett–Teller (BET) surface area of 236 m2 g–1, pore volume of 0.229 cm3 g–1, and robust nature of FePO-1-2 have motivated us to explore its catalytic activity in liquid phase partial oxidation reactions under green conditions. FePO-1-2 exhibits excellent catalytic activity (96% product selectivity, 72% conversion) for selective liquid phase oxidation of cyclohexanone to adipic acid in the presence of molecular ...

The outlook of zeolite-Y hampered metal–ligand framework as heterogeneous catalysts: synthesis, spectral account and catalytic features

Zeolite-Y enslaved complexes were prepared by the Flexible ligand method. Synthesized materials were characterized by various spectral tools like powder X-ray diffraction, spectral studies (UV–Vis and FT-IR), chemical analysis (ICP-OES and elemental), scanning electron microscopy, AAS and 1H-NMR techniques. Further, BET and thermogravimetric (TG) analysis were also done for characterization of surface area, pore volume, thermal behavior, and related parameters. Baeyer–Villiger oxidation of cyclohexanone was carried out over Zeolite-Y enslaved complexes using hydrogen peroxide (H2O2) as an oxidant. The performance of the heterogeneous system with the homogeneous system was compared to determine the protection effect of the zeolitic matrix over the active center on the catalytic properties. In addition, the effect of experimental variables (various solvents, amount of catalyst, the mole ratio of substrate and oxidant, temperature, and reaction time) was examined in order to get absolute reaction conditions. Under the optimized reaction conditions, [Fe(nbab)2]-Y was found to be a potential candidate, achieving 70 % ɛ-caprolactone selectivity.