Formation Of Cyclohexanone Research Articles

Phenol hydrogenation over H-MFI zeolite encapsulated platinum nanocluster catalyst.

The development of catalysts with high activity and selectivity is of paramount importance for the industrial conversion of biomass. One crucial reaction in this process is the hydrogenation of phenol, a key component of phenolic resins in biomass, into cyclohexanone and cyclohexanol. In this study, density functional theory (DFT) calculations were utilized to examine phenol hydrogenation reaction mechanisms over a platinum (Pt) nanocluster encapsulated in the H-MFI zeolite, e.g., Pt6@H-MFI. Various anchoring positions of the Pt6 nanocluster on the H-MFI framework and the adsorption configurations of phenol on the Pt6@H-MFI were firstly determined. DFT calculation results demonstrate that, compared to the Pt surface, the Pt6@H-MFI catalyst shows high hydrogenation activity with a notable selectivity towards cyclohexanol. The pathway leading to the formation of cyclohexanol is both kinetically and thermodynamically more favorable over the pathway leading to the formation of cyclohexanone. The present work offers significant contributions to the strategic development of catalysts consisting of metal nanoclusters encapsulated within zeolite frameworks.

Selective hydrogenation of phenol to cyclohexanone over small amount of Ru-promoted Pd/ZrHP catalysts

Selective hydrogenation of phenol to cyclohexanone is a vital step in the manufacture of fiber (nylon), which is currently carried out over expensive Pd catalyst with low productivity. In this work, a series of Ru-promoted Pd catalysts were synthesized in a facile microwave-assisted method and tested in the hydrogenation of phenol to cyclohexanone. It was found that small amount of Ru in Ru-Pd alloy can increase the conversion of phenol obviously without loss of cyclohexanone selectivity. The selectivity of cyclohexanone over Ru0.15Pd4.85/ZrHP remained higher than 99%, while the conversion of phenol increased from 20.5% (over Pd5/ZrHP) to 97.9% at 100 °C and 1 MPa. And the highest turnover frequency (TOF) of surface metal in Ru0.15Pd4.85/ZrHP at 100 °C and 2 MPa reached 1605 h−1. Characterization results revealed that the addition of Ru can improve the dispersion of Ru-Pd alloy and enhance its electron density. In addition, the activated hydrogen on Ru-Pd alloy and acid sites in ZrHP played a synergistic effect for the selective formation of cyclohexanone from phenol.

Effect of precipitating agents on activity of co-precipitated Cu–MgO catalysts towards selective furfural hydrogenation and cyclohexanol dehydrogenation reactions

The major industrial application and study of hydrogenation of furfural-to-furfural alcohol and dehydrogenation of cyclohexanol to cyclohexanone, over different precipitating agents namely K2CO3, Na2CO3, KOH, NH3 and (COOH)2.2H2O was carried out in vapour phase reactor. Efforts were made to study the effect of these different precipitating agents on Cu–MgO catalyst and its activity towards the hydrogenation and dehydrogenation reactions due to its industrial applications. The prepared co-precipitated Cu–MgO catalysts were characterized by using various modern analytical and spectroscopic techniques which include FE-SEM, BET, XRD, XPS, TPR and DTA. The characterization data revealed that different precipitating agents strongly influenced the physiochemical properties of the developed heterogeneous catalysts. Additionally, FE-SEM images revealed that employing different precipitating agents resulted in various morphologies for the final catalysts. The hydrogenation and dehydrogenation reactions over the Cu–MgO catalyst revealed that the catalyst prepared by K2CO3 as precipitating agent exhibited high catalytic activity. Meanwhile, The presence of more Cuo/Cu+ species on this catalyst with smaller Cu crystallite size as evidenced by XPS and XRD results seems to be accountable for its high activity towards the formation of furfural alcohol and cyclohexanone compared to the other catalysts with different precipitating agents. Additionally, the time on stream (T.O.S) studies performed and it revealed that the catalyst was fairly stable for 300 min showing consistency in its activity towards both reactions. The yield obtained for furfural alcohol and cyclohexanone was 97% and 64%, respectively.

Catalytic Hydrogenation of Nitrocyclohexane with CuCo/SiO2 Catalysts in Gas and Liquid Flow Reactors

Catalytic hydrogenation of nitrocyclohexane proved to be an attractive alternative source of various chemical compounds: cyclohexanone oxime, cyclohexanone, cyclohexanol, cyclohexylamine and dicyclohexylamine. A growing interest in this reaction has been observed in the last few years. Herein, we present the catalytic performance of Cu/SiO2, Co/SiO2 and CuCo/SiO2 in gas and liquid flow nitrocyclohexane hydrogenation. The analysis of synthesized catalysts morphology (BET, TPR, XRD, TEM) in terms of their catalytic behavior allows us to draw general conclusions and determine the optimal conditions for the production of desired products. Application of the monometallic copper leads to the formation of cyclohexanone as the main product, but with low activity. On the other hand, Co/SiO2 shows high activity but gives cyclohexylamine. Bimetallic system CuCo(3:1)/SiO2 allows for the efficient production of 100% cyclohexanone at 5 bar and 75 °C.

Photothermal oxidation of cyclohexane over CoLaOx/WO3 Z-scheme composites with p-n heterojunction in solvent-free conditions

Photothermal oxidation of cyclohexane with molecular oxygen in solvent-free is considered to be an efficient approach for the formation of cyclohexanone and cyclohexanol (KA oil), and possesses the potential to generate the next stage product of adipic acid (AA) by one-pot oxidation in chemical industry. Herein, a unique type of Co8La1Ox/WO3 Z-scheme nanocomposites with p-n heterojunction was successfully constructed by a facile process of solvothermal reaction in conjunction with the simple impregnation method. The Co8La1Ox/WO3 Z-scheme heterojunction nanocomposites achieved an excellent catalytic performance for the photothermal oxidation of cyclohexane at 120 ℃ under visible light in solvent-free conditions. Surprisingly, 10.35% conversion of cyclohexane with 98.75% selectivity of KA oil (liquid, 80.97%) and AA (solid, 17.78%) was achieved during the reaction time of 3 h. Moreover, the desirable durability and stability of the Co8La1Ox/WO3 composites demonstrated a potential application as an industrial catalyst. The outstanding catalytic performance of the Co8La1Ox/WO3 composites could be ascribed to the enhanced electron excitation capacity, the accelerated electron-hole separation and migration, the inhibited charge recombination, the strong visible-light absorption, and the efficient synergetic catalytic effect of photo-thermo. Besides, high oxygen adsorption capacity and large specific surface area of the Co8La1Ox/WO3 composites can efficiently build a bridge between cyclohexane and O2 to fully utilize the oxygen participation in the oxidation. The present approach provides a promising perspective for the designing and constructing of Z-scheme heterojunction catalyst with a high-efficiency photo-thermo catalytic performance in the oxidation of cyclohexane to KA oil and AA in chemical industry.

A multi-technique approach to unveil the redox behaviour and potentiality of homoleptic CuI complexes based on substituted bipyridine ligands in oxygenation reactions.

The effect of differently substituted 2,2'-bipyridine ligands (i.e. 6,6'-dimethyl-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, 6,6'-dimethoxy-2,2'-bipyridine and 2,2'-bipyridine) on the reversible oxidation of the resulting CuI homoleptic complexes is investigated by means of a multi-technique approach (electronic and vibrational spectroscopies, DFT, electrochemistry). Among the four tested complexes, [CuI(6,6'-dimethyl-2,2'-bipyridine)2] (PF6) shows a peculiar behavior when oxidized with an organic peroxide (i.e. tert-butyl hydroperoxide, tBuOOH). The simultaneous use of UV-Vis-NIR and Raman spectroscopy methods and cyclovoltammetry, supported by DFT based calculations, allowed identifying (i) the change in the oxidation state of the copper ion and (ii) some peculiar modification in the local structure of the metal leading to the formation of a [CuIIOH]+ species. The latter, being able to oxidize a model molecule (i.e. cyclohexene) and showing the restoration of the original CuI complex and the formation of cyclohexanone, confirms the potential of these simple homoleptic CuI complexes as model catalysts for partial oxygenation reactions.

To the question of oxidation on the surface of oxides: temperature- programmed oxidation of cyclohexanol

Temperature-programmed reaction (TPR) method with mass spectrometric control of the products was used to study of cyclohexanol oxidation into cyclohexanone on individual and mixed oxides supported by γ-Al2O3 and silica gel. In the TPR profiles the temperature of a maximum rate of cyclohexanone formation varies from 125°C for MoO3/Al2O3 to 235°C for less active CuO/Al2O3. The catalytic activity of individual oxides decreases in the order MoO3/Al2O3> V2O5/SiO2 > Fe2O3/Al2O3 > Bi2O5/Al2O3 > TiO2/SiO2 ≈ СeO2/Al2O3 > TiO2/Al2O3 > SnO2/Al2O3. As "reactive" oxygen in our TPR experiment was supplied only from oxide lattice, oxide activity is determined by different energy of the surface Me – O bonds. The approach to search for mixed active oxides based on decreasing coordination number of O2- ions is proposed, that confirmed by the example of CuO-WO3/Al2O3 catalyst. The mixed supported oxides, especially CuOCrO3/Al2O3, CuO-MoO3/Al2O3, MoO3-SnO2/Al2O3 and Bi2O3–SnO2/Al2O3, are more active in С6Н12О + 1/2О2 → С6Н10О + Н2О oxidation. The synthesized CuO-CrO3/Al2O3 catalyst provides cyclohexanone formation without side cyclohexanol dehydration and can be used for the oxidation of ethylene glycol – methanol mixture into methyl glycolate. CuO-Cr2O3/Al2O3 with a spinel structure of CuCr2O4 ([CuO4] 6− tetrahedra, Cu2+ sp3-hybridization) is more active in cyclohexanol oxidation than CuO/Al2O3 with flat [CuO4] 6−squares, Cu2+ dsp2-hybridization. This is explained by the lower energy of Cu-O bonds at sp3-hybridization of Cu2+ ions.

Upgrading lignin derived monomers over basic supported metal catalysts

Catalytic upgradation of aromatic monomers derived from lignin depolymerization is of high interest for the production of sustainable fuels and chemicals. Basic support has potential to provide advantages of better substrate-support interaction and reduced coke formation. Hence, we report the effect of various basic supports for metal catalysts (Pt, Pd, Ru) on the upgradation of phenol, guaiacol and eugenol. The complete hydrogenation product is achieved due to the strong interaction of the substrate with catalyst. Phenol is converted (55%) into cyclohexanol (49% yield) with low loading of Pt catalyst (1 wt%), supported by the higher TON of 1 wt%Pt/NaX (TON = 14844) than 3 wt%Pt/NaX (TON = 5128). Effect of basic support with moderate (NaX) and strong (C-HT) basic strengths are corelated for the higher cyclohexanone formation. Presence of strong basic sites and higher TON of 3 wt% C-HT (TON = 6806) directs the significant substrate-support interaction. Catalytic activity and recyclability are supported by the comparable performance of recycle runs and characterizations of the fresh and spent catalysts.

Towards the selectivity distinction of phenol hydrogenation on noble metal catalysts

Abstract Selective hydrogenation of phenol to cyclohexanone is intriguing in chemical industry. Though a few catalysts with promising performances have been developed in recent years, the basic principle for catalyst design is still missing owing to the unclear catalytic mechanism. This work tries to unravel the mechanism of phenol hydrogenation and the reasons causing the selectivity discrepancy on noble metal catalysts under mild conditions. Results show that different reaction pathways always firstly converge to the formation of cyclohexanone under mild conditions. The selectivity discrepancy mainly depends on the activity for cyclohexanone sequential hydrogenation, in which two factors are found to be responsible, i.e. the hydrogenation energy barrier and the competitive chemisorption between phenol and cyclohexanone, if the specific co-catalyzing effect of H2O on Ru is not considered. Based on the above results, a quantitative descriptor, Eb(one/pl)/Ea, in which Ea can be further correlated to the d band center of the noble metal catalyst, is proposed by the first time to roughly evaluate and predict the selectivity to cyclohexanone for catalyst screening.

Fe(III) Complexes in Cyclohexane Oxidation: Comparison of Catalytic Activities under Different Energy Stimuli

In this study, the mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (1) derived from Nʹ-acetylpyrazine-2-carbohydrazide (H2L) was synthesized and characterized by several physicochemical methods, e.g., elemental analysis, infrared (IR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single crystal X-ray diffraction analysis. The catalytic performances of 1 and the previously reported complexes [Fe(HL)Cl2] (2) and [Fe(HL)Cl(μ-OMe)]2 (3) towards the peroxidative oxidation of cyclohexane under three different energy stimuli (microwave irradiation, ultrasound, and conventional heating) were compared. 1-3 displayed homogeneous catalytic activity, leading to the formation of cyclohexanol and cyclohexanone as final products, with a high selectivity for the alcohol (up to 95%). Complex 1 exhibited the highest catalytic activity, with a total product yield of 38% (cyclohexanol + cyclohexanone) under optimized microwave-assisted conditions.

Rh nanoclusters encaged in hollow mesoporous silica nanoreactors with enhanced catalytic performance for phenol selective hydrogenation

Here, we report the synthesis of Rh nanoclusters (~0.8 nm) encapsulated in hollow mesoporous silica nanoreactors (Rh@HMSNs) for phenol selective hydrogenation. Specifically, triple ligands were used to bind Rh3+ ions to form negatively charged coordination complex network, which further combines by electrostatic attraction with positively charged diblock copolymers to obtain Rh3+ ions bound polymer micelles. Following silica deposition onto micelles, calcination and H2 reduction result in hollow mesoporous silica nanoreactors and residence of Rh nanoclusters close to their hollow cavities. Relative to the control silica supported Rh catalysts, the obtained Rh@HMSNs show significantly enhanced catalytic activity, cyclohexanol selectivity and stability for phenol hydrogenation. By DFT theoretic calculations and comparison of control experiments, the performance enhancement of Rh@HMSNs is ascribed to their unique nanostructures, where the small size of Rh nanoclusters increases the cyclohexanol selectivity by suppressing the formation of cyclohexanone, and the residence of Rh nanoclusters close to hollow cavities enhances their thermal and catalytic stability.

Selective photocatalytic oxidation of cyclohexanol to cyclohexanone: A spectroscopic and kinetic study

In this work, spectroscopic and kinetic studies were performed on photocatalytic oxidation of cyclohexanol to cyclohexanone. The photocatalytic experiments were performed according to a three-level full factorial design and the rate of cyclohexanone production was determined by HPLC analysis. In situ ATR-FTIR analysis of the photocatalytic reaction revealed that cyclohexanol can be selectively converted to cyclohexanone, without the formation of significant amounts of carbonates and carboxylates. A reaction mechanism based on different steps from charge separation to cyclohexanone molecule formation is proposed. The results were utilized to determine the kinetic parameters (with the help of genetic algorithm) and validate the model. The developed kinetic model illustrates that the rate of cyclohexanone production increases as a power function with respect to the light intensity and decreases as an exponential function with respect to time. An excellent selectivity of cyclohexanone was confirmed by spectroscopic and chromatographic studies. This study demonstrates that photocatalysis can be a promising technology for formation of cyclohexanone from cyclohexanol.

Synthesis of Ni Catalyst Supported on SiO2-ZrO2 Binary Oxide for Hydrodeoxygenation of Phenol

Hydrodeoxygenation is a one-step reaction that involve the hydrogenation of unsaturated carbon followed with the deoxygenation of the carbon-oxygen bond. This reaction is effective for converting biomass-derived chemicals from bio-oils, fats, woods, and lignocellulosic materials into biofuels using metal-based oxide catalysts. A Ni based-metal oxide catalyst is reported for hydrodeoxygenation reaction of phenol. The catalyst was prepared by a wet-impregnation method using Ni(NO3)2.6H2O dissolved in deionized water and mixed with the previously prepared SiO2-ZrO2 binary oxide as support. After calcination and reduction at 500 °C, Ni/SiO2-ZrO2 catalyst was obtained. The XRD results showed 2θ peaks for metallic Ni at 30°, 44° and 76°. Additional peaks were detected at 2θ = 35°, 50°, 51°, and 60° for ZrO2 tetragonal phase. However, peaks were not detected for SiO2 suggesting amorphous SiO2-ZrO2 composite formation. The XRF analysis of Ni loading was detected at 16.45%. The catalyst activity test for hydrodeoxygenation of phenol was performed using a batch reactor at 200 °C for 2 h and 8 h. The GC-MS analysis gave product conversion for 2 h at 16.84% with the selectivity formation of cyclohexanol and cyclohexanone at 48.10% and 45.78% yield, respectively. After a prolonged reaction time of 8 h, 100% selectivity for cyclohexanol was achieved. Product distribution showed that the catalyst is active for hydrogenation of benzene better than -OH or C=O deoxygenation. The results suggest Ni/SiO2-ZrO2 could be a potential catalyst for biofuel production via hydrogenation reaction.

Effect of Support on the Hydrodeoxygenation of Phenol using Ni-based Metal Catalysts: Ni/SiO2, Ni/ZrO2, and Ni/Al2O3

Hydrodeoxygenation (HDO) reaction is a fundamental step for producing bio-oil from lignocellulosic biomass. One of the major components from biomass is lignin which can be hydrolysed into phenolic derivatives. Here, we reported the preparation of Ni-based metal catalysts with the variation of a metal oxide for HDO of phenol. The Ni loading for each metal oxides is 15% (w/w), supported on SiO2, ZrO2, and Al2O3. The XRD analysis showed that Ni metal was detected in the SiO2 support at 2θ = 44.26°, 51.72°, 76.5°; Ni in ZrO2 at 2θ = 44.55°, 51.9°, 76.4°; and Ni in Al2O3 at 2θ = 44.12°, 51.72°, and 76.78°. The catalytic test for HDO reaction was carried out in the autoclave oil batch reactor, heated for 2 hours at 200°C with H2 gas atmosphere. Based on GC-MS analysis, the reaction at 200°C usingNi-SiO2 gave the highest product conversion, that is 52.2% with the selective formation of 2-methyl-1-butanol (52.2%). On the other hand, the reaction using Ni/ZrO2 only produce 17.64% of the products with selective formation of cyclohexanone (35.35%). The result showed that products distribution is significantly affected by the type of the support.

Ti3+ self-doped TiO2 as a photocatalyst for cyclohexane oxidation under visible light irradiation

Most of TiO2 particles can be used as a photocatalyst for the selective oxidation of cyclohexane under ultraviolet light illumination. In this paper, Ti3+ self-doped TiO2 submicron-sized particles (i.e., Ti3+/TiO2 SMP) were used as a catalyst for visible-light driven photocatalytic cyclohexane oxidation. The microstructure and properties of the Ti3+/TiO2 SMP were characterized by X-ray diffraction (XRD), UV–visible diffuse reflection (UV–Vis DRS), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), solid-state photoluminescence spectroscopy (PLS) and X-ray photoelectron spectroscopy (XPS). The Ti3+/TiO2 SMP exhibits good visible-light driven photocatalytic performances for cyclohexane oxidation with cyclohexanone as a dominate product. Effects of solvent, reaction temperature, reaction time and oxygen pressure on the formation of cyclohexanone were investigated. The cyclohexane oxidation over the Ti3+/TiO2 SMP photocatalyst using carbon tetrachloride as a solvent under the optimal conditions presents a greater selectivity to cyclohexane (i.e., 95.1%). Based on the controlled experimental results with different radical scavengers, the hole (h+) is critical for the activation of cyclohexane.

Self-Condensation of Enaminodiones as a Method for Benzene Ring Construction: Synthesis of Diacyl-Substituted Phenols and Catechols.

A novel transition metal-free approach for the construction of the benzene core has been developed through self-condensation of available enaminodiones. Functionalized acyl-substituted phenols and catechols were obtained in 29-97% yields with high chemoselectivity under mild conditions. This base-promoted formal [4+2] annulation proceeds via cyclohexanone formation and involves the cascade transformation based on double Michael addition and aromatization (retro-Claisen cleavage and amine elimination).

Liquid-phase oxidation of cyclohexane. Cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone, mechanisms of formation and transformation

The mechanisms of formation and transformation of cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone in the liquid-phase oxidation of cyclohexane are reviewed. Cyclohexyl hydroperoxide is formed in chain propagation reactions and decomposes via the degenerate branching reactions under the action of alkoxyl, alkyl, and peroxyl radicals, as well as via nonradical channels to form alcohol and ketone. The radicals of two types, $${\rm{H}}{{\rm{O}}_2}^ \cdot $$ radical and α-hydroxycyclohexylperoxyl radical, are involved in chain propagation in the course of cyclohexanol oxidation. In the chain propagation reactions, $${\rm{H}}{{\rm{O}}_2}^ \cdot $$ radicals are more reactive than α-hydroxycyclohexylperoxyl radicals. The dynamic equilibrium was established in the dissociation of 1-hydroxycyclohexylperoxyl radical to cyclohexanone and radical $${\rm{H}}{{\rm{O}}_2}^ \cdot $$ . During oxidation of cyclohexane, cyclohexanone is formed from peroxyl radicals, as well as by the decomposition of cyclohexyl hydroperoxide and chain-radical oxidation of cyclohexanol. The oxidation of cyclohexanone in positions 2 and 6 affords 2-hydroperoxycyclohexanone, which predominantly decomposes to form 2-hydroxycyclohexanone. The oxidation of 2-hydroxy-cyclohexanone proceeds via the main channels of destruction of the carbon chain of cyclohexane leading to adipic acid and adipic anhydride. The oxidation products of C—H bonds of all types in alcohol and ketone are accumulated simultaneously with the oxidation products of C(1)—H bonds in cyclohexanol and of C(2)—H and C(6)—H bonds in cyclohexanone.

Density functional theory study of selective aerobic oxidation of cyclohexane: the roles of acetic acid and cobalt ion.

A computational study of cyclohexane autoxidation and catalytic oxidation to a cyclohexyl hydroperoxide intermediate (CyOOH), cyclohexanol, and cyclohexanone has been conducted using a hybrid density functional theory method. The activation of cyclohexane and O2 is the rate-determining step in the formation of CyOOH due to its relatively high energy barrier of 41.2kcal/mol, and the subsequent reaction behavior of CyOOH controls whether the production of cyclohexanol or cyclohexanone is favored. Using CH3COOH or (CH3COO)2Co as a catalyst reduces the energy barriers required to activate cyclohexane and O2 by 4.1 or 7.9kcal/mol, respectively. Employing CH3COOH improves the CyOOH intramolecular dehydration process, which favors the formation of cyclohexanone. The energy barrier to the decomposition of CyOOH to CyO·, an important precursor of cyclohexanol, decreases from 35.5kcal/mol for autoxidation to 25.9kcal/mol for (CH3COO)2Co catalysis. (CH3COO)2Co promotes the autoxidation process via a radical chain mechanism. The computational results agree with experimental observations quite well, revealing the underlying role of CH3COOH and Co ion in cyclohexane oxidation. Graphical abstract Through DFT analysis of cyclohexane autoxidation and catalytic oxidation, we reveal the mechanism of the effects of CH3COOH and Co2+ on the reaction routes.

Supercritical water gasification of phenol over Ni-Ru bimetallic catalysts

Incorporating Ru in a Ni catalyst for gasification of phenol in supercritical water at 450 °C and 30 min promoted formation of cyclohexanol via hydrogenation, which is a key step toward gasification. Both Ni and Ni-Ru catalysts were effective to reduce the formation of cyclohexanone and oligomerization products, compared with the case with no catalyst. H2 and CH4 yields increased as the Ru/Ni ratio increased, as did the carbon and hydrogen yields in the gas phase products. The Ni80Ru20/Al2O3 catalyst provided good gasification performance and it exhibits Ru (101), Ru (100) and Ni (111) facets and evidence of overlaid bimetallic particles. DFT calculations show that the presence of Ru (either as pure Ru or as a Ni-Ru alloy) reduces the energy barrier for phenol hydrogenation by close to 0.2 eV relative to pure Ni, and that the energy barrier is not as largely affected by the amount of Ru present, provided it is non-zero.

INTENSIFICATION OF THE CYCLOHEXANE LIQUID PHASE OXIDATION PROCESS

Liquid-phase oxidation of cyclohexane to cyclohexanol and cyclohexanone was studied in the absence of solvents under an air pressure of 0.5-5 MPa, in the temperature range 115-150 °C, catalyzed by N-hydroxyphthalimide (N-HPI). It was established for the first time that the use of N-HPI as a catalyst in place of the conventionally used metal salts of variable valence allowed a 2-3-fold increase in the conversion of the initial hydrocarbon and selectivity from 70-75 to 90%. The combined use of N-HPI with cobalt(II) acetate results in an additional increase in the conversion of cyclohexane by 30-40%, the selectivity of cyclohexanol and cyclohexanone formation to 94-97%, which seems to be due to the synergistic effect between the two components of the catalyst. The mechanism of catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone is discussed. It has been suggested that N-HPI plays a dual role in the oxidation of cyclohexane: it catalyzes the conversion of cyclohexane to cyclohexanol and cyclohexanone and, on the other hand, promotes the conversion of cyclohexanol to cyclohexanone, thereby substantially reducing the formation of adipic acid and its esters, by-products of the reaction, and increases selectivity of oxidation. This also explains the unusually high (1.3-1.5 : 1) ketone: alcohol ratio in the oxidation products of cyclohexane in the presence of N-HPI. The high selectivity of the formation of the desired products, the conversion of cyclohexane, the moderate temperature, the available catalyst, suggest that this method of oxidizing cyclohexane to cyclohexanol and cyclohexanone may be of interest for further practical use.