Cyclohexanone Selectivity Research Articles

Baeyer-Villiger Oxidation of Cyclohexanone Catalyzed by SBA-15 Supported Silicotungstic Acid

Silicotungstic acid (H4O40SiW12) was supported on SBA-15 with the content of 20% by impregnation. The structure and proper-ties of the catalyst were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption-desorption, and transmis-sion electron microscopy. H4O40SiW12 was highly dispersed on SBA-15 without structural change. The material was applied as an efficient catalyst for the Baeyer-Villiger oxidation of cyclohexanone under different conditions such as the catalyst amount, reaction temperature, and reaction time. When 10 mg of catalyst was used, the cyclohexanone conversion and selectivity for lactone were up to 86% and 99%, respec-tively, at 70 oC for 8 h. The catalyst had moderate reusability in the oxidation system.

氯代苯胺液相催化加氢合成环己酮

A method for the degradation of chloraniline for high selective synthesis of cyclohexanone was proposed. The cyclohexanone was synthesized from multichloraniline (2,4,6-trichloroaniline and 2,4-dichloroaniline) with a high selectivity (without cyclohexanol) over a La modified Pd/Al2O3 catalyst. The conversion of the hydrogenation of 2,4,6-trichloroaniline and 2,4-dichloroaniline are both 100%, and the corresponding selectivity of cyclohexanone are 98.6% and 100% (cyclohexanol was not detected), respectively, under the optimal reaction conditions. Chloraniline was first underwent hydrodechlorination/ N -methylation reactions to form intermediates such as aniline, N -methylaniline, N , N -dimethylaniline, etc. on the surface of the Pd/La-Al2O3 catalyst. Then cyclohexanone was produced from the ring hydrogenation and amino-group hydrolysis/alcoholysis of these intermediates. The presence of Cl in the chloraniline molecular and water in the reaction system is important for the selectivity of cyclohexanone.

Self-assembly preparation of Au/SiO2 catalyst and its catalysis for cyclohexane oxidation with air

Au/SiO2 catalysts were prepared by self-assembly technique and characterized by EDS, XRD, XPS, AAS and N2 adsorption/desorption. They were found to be very efficient catalysts for the selective oxidation of cyclohexane with air in the absence of any solvent or promoter. The influences of Au loading, reaction temperature, reaction pressure and reaction time on the catalytic activity were explored in detail. Under suitable reaction conditions, the conversion of cyclohexane and total selectivity of cyclohexanone and cyclohexanol were up to ~10 and ~92%, respectively.

Immobilization of anionic metalloporphyrins on zinc hydroxide nitrate and study of an unusual catalytic activity

This paper is the first report on the immobilization of an anionic iron(III) porphyrin family on zinc hydroxide nitrate ( ZHN), a layered hydroxide salt. ZNH was prepared by means of a precipitation reaction between a zinc nitrate solution and ammonium hydroxide. Two immobilization systems were investigated, namely magnetic stirring at room temperature and stirring/reflux in an ethanolic solution. The solids were characterized by powder X-ray diffraction (XRD), electron paramagnetic resonance (EPR), thermogravimetric and derivative thermogravimetric (TGA/DTG), transmission electron microscopy (TEM), as well as ultraviolet–visible (UV–Vis) and Fourier transform infrared (FTIR) spectroscopic analyses. The catalytic activity of the materials was investigated in the oxidation of cyclooctene, cyclohexane, and n-heptane using iodosylbenzene as oxygen donor. The oxidation products were analyzed by gas chromatography. The results revealed an unusual selectivity for cyclohexanone in the reactions of cyclohexane oxidation catalyzed by the anionic iron(III) porphyrins immobilized onto ZHN. These results suggest that the structure of the ZHN support influences the catalytic mechanism and that cyclohexane oxidation occurs via a radicalar pathway.

Influence of Acid Modification on Selective Phenol Hydrogenation Over Pd/Activated Carbon Catalysts

The influence of the acid treatment on cyclohexanone selectivity of phenol hydrogenation over Pd on active carbon was studied in liquid phase reaction and by temperature-programmed desorption. Acid treatment of activated carbon led to an increased cyclohexanone/cyclohexanol ratio. Acid modification of the carbon support enriched the electron density of Pd, and enhanced the desorption of the phenoxy species, which resulted in improved cyclohexanone selectivity in phenol hydrogenation.

Lanthanum-promoted Pd/Al2O3 catalysts for liquid phase in situ hydrogenation of phenol to cyclohexanone

A series of lanthanum-promoted Pd/Al2O3 catalysts (Pd/La x –Al2O3), for the liquid phase in situ hydrogenation of phenol into cyclohexanone, was prepared by the incipient wetness impregnation method. Addition of lanthanum to Pd/Al2O3 enhances the TOF of the catalyst for the liquid phase in situ hydrogenation of phenol significantly. The conversion of phenol is highly dependent upon the atomic ratio of La/Pd, but the presence of lanthanum has little effect on the selectivity of cyclohexanone. The selectivity of cyclohexanone in the liquid phase in situ hydrogenation of phenol over the Pd/La x –Al2O3 catalyst is as high as 98%, which is quite higher than the hydrogenation using H2 (67.4%). Results from BET, EDS, CO chemosorption, XRD and H2-TPR suggest that the presence of suitable amounts of lanthanum improves the Pd dispersion on the support. The peak temperature for the reduction of PdO in the H2-TPR moves to higher in the presence of lanthanum. Additionally, the Pd particles could adhere to the lanthanum rather than the Al2O3.

Selective Oxidation of Cyclohexane Catalyzed by Metallo-Deuteroporphyrins in Homogeneous Solution

To search for the efficient biomimetic catalysts for the oxidation of hydrocarbon,cobalt deuteroporphyrin [Co(DPDME)] was used as catalyst for the oxidation of cyclohexane with air.The effects of reaction temperature,pressure of air,the catalyst amount and different complexes were evaluated.The experiment results show that Co(DPDME) is more effective than the others,and the optimum reaction conditions for the oxidation of cyclohexane are:c=0.015 mmol/L,reaction temperature 423 K,pressure of air 0.8 MPa,reaction time 5 h.Under the optimum conditions,the conversion rate of cyclohexane could reaches to 18.2%,the total selectivity of cyclohexanol and cyclohexanone is 87.4%.The temperature has much more influence on the catalytic reaction.Although the stability of Co(DPDME) was reduced when the temperature is higher than 443 K,the turnover number reaches 66 646.We also discussed the possible reaction path of Co(DPDME)-catalyzed oxidation of cyclohexane with oxygen.

Catalytic oxidation of cyclohexane over Ti–Zr–Co catalysts

Ti–Zr–Co alloys have been fabricated and characterized, and their catalytic performance was discussed for the oxidation of cyclohexane with oxygen under solvent-free condition. The icosahedral quasicrystalline phase (I-phase)-forming ability of Ti–Zr–Co alloys with different compositions was discussed, and it was confirmed that I-phase could be formed as a dominating phase at the Ti-rich composition region from Ti 53Zr 27Co 20 to Ti 75Zr 5Co 20 in as-cast alloys. The composition and microstructure of Ti–Zr–Co alloys present crucial influences on its catalytic activity and selectivity in the oxidation of cyclohexane. The influences of some reaction parameters such as temperature, reaction time, and catalyst amounts were also investigated. Ti 70Zr 10Co 20 alloy containing quasicrystal microstructure showed good catalytic performance with a 6.8% conversion of cyclohexane and 90.4% selectivity of cyclohexanol and cyclohexanone. It behaves as an efficient heterogeneous catalyst for the oxidation of cyclohexane and could be recycled five times without loss in activity and selectivity.

Catalytic Aerobic Oxidation of Cyclohexane and Ethyl Benzene Over Chromium-Containing Mesoporous Organosilicas

Chromium-containing ethane-bridged hybrid periodic mesoporous organosilicas (Cr-PMO) were synthesized using 1,2-bis(triethoxysilyl)ethane (BTEE) and tetraethyl orthosilicate (TEOS) as silica sources and alkyltrimethyl ammonium salts as surfactants by two different synthesis routes. PXRD and N2 adsorption–desorption analysis shows that the original structure of the materials is maintained after chromium substitution while spectroscopic study proves the incorporation of chromium in the frame wall positions and show the existence of Cr2O3 species in the mixed silica source (BTEE-TEOS) synthesized chromium samples. The catalytic activity of the newly developed chromium samples was evaluated in the liquid phase oxidation of cyclohexane and ethylbenzene using air as an oxidant. Further, the Cr-PMO samples exhibited better cyclohexane conversion and cyclohexanone selectivity than the conventional Cr-MCM-41 and other metal-containing MCM-41 samples. The exceptional activity of the new chromium-containing molecular sieves is attributed to the hydrophobicity of the materials and to the complementary structural features that facilitates the accessibility of substrate to the active framework chromium sites.

Hydrogenation of Phenol in Supercritical Carbon Dioxide Catalyzed by Palladium Supported on Al‐MCM‐41: A Facile Route for One‐Pot Cyclohexanone Formation

AbstractThe hydrogenation of phenol has been carried out in supercritical carbon dioxide (scCO2) under very mild reaction conditions at the temperature of 50 °C over palladium supported Al‐MCM‐41 (metal loading ∼1%). This palladium catalyst is shown to be highly active and promotes the selective formation of cyclohexanone (∼98%), an industrially important compound, in a “one‐pot” way. The effects of different variables like carbon dioxide and hydrogen pressure, reaction time and also silica/alumina ratio of the MCM‐41 support along with palladium dispersion are presented and discussed. The pressure effect of carbon dioxide is significantly prominent in terms of conversion and cyclohexanone selectivity. Moreover, the silica/alumina ratio was also found to be an important parameter to enhance the effectiveness of the catalyst as it exhibits a remarkable increase in phenol conversion from 20.6% to 98.4% as the support changes from only silica MCM‐41 to Al‐MCM‐41. A plausible mechanism for the hydrogenation of phenol to cyclohexanone over the palladium catalyst has been proposed. The proposition is validated by transition state calculations using density functional theory (DFT), which reveal that cyclohexanone is a favorable product and stabilized by <19 kcal mol−1 over cyclohexanol in scCO2 medium. Under similar reaction conditions, phenol hydrogenation was also carried out with rhodium, supported on Al‐MCM‐41. In contrast to the palladium catalyst, a mixture of cyclohexanone (57.8%) and cyclohexanol (42.2%) was formed. Detailed characterization by X‐ray diffraction and transmission electron microscopy confirmed the presence of metal nanoparticles (palladium and rhodium) between 10–20 nm. Both the catalysts exhibit strikingly different product distributions in solventless conditions compared to scCO2. This method can also be successfully applied to the other hydroxylated aromatic compounds.

Photocatalytic activity of Ag-substituted and impregnated nano-TiO 2

Ag-substituted (Ag sub) and Ag-impregnated (Ag imp), anatase phase nano-TiO 2 have been synthesized by solution combustion technique and reduction technique, respectively. The catalysts were characterized extensively by powder XRD, TEM, XPS, FT-Raman, UV absorption, FT-IR, TGA, photoluminescence, BET surface area and isoelectric pH measurements. These catalysts were used for the photodegradation of dyes and for the selective photooxidation of cyclohexane to cyclohexanone. The photoactivities of the combustion-synthesized catalysts were compared with those of commercial Degussa P 25 (DP 25) TiO 2, and Ag-impregnated DP 25 (Ag DP). For the photocatalytic degradation of dyes, unsubstituted combustion-synthesized TiO 2 (CS TiO 2) exhibited the highest activity, followed by 1% Ag imp and 1% Ag sub. For the photoconversion of cyclohexane, the total conversion of cyclohexane and the selectivity of cyclohexanone followed the order: 1% Ag sub > DP 25 > CS TiO 2 > 1% Ag imp > 1% Ag DP. The kinetics of the photodegradation of dyes and of the photooxidation of cyclohexane were modeled using Langmuir–Hinshelwood rate equation and a free radical mechanism, respectively, and the rate coefficients were determined. The difference in activity values of the catalysts observed for these two reactions and the detailed characterization of these catalysts are described in this study.

Magnetic CoFe 2O 4 nanocrystal: A novel and efficient heterogeneous catalyst for aerobic oxidation of cyclohexane

Magnetic nanocrystalline spinel-type cobalt ferrite complex oxides were prepared by a simple sol–gel auto-combustion method at five different molar ratios of Co II to Fe III (1:4.0, 1:2.8, 1:2.0, 1:1.5, and 1:1.1) and characterized by X-ray diffractometry (XRD), Fourier transform infrared spectrophotometry (FT-IR) and transmission electron microscopy (TEM). Their catalytic performance was evaluated in the oxidation of cyclohexane with oxygen as oxidant in the presence of neither solvents nor reducing agents. It has been revealed that the catalysts had high catalytic activities for heterogeneous oxidation of cyclohexane. Especially, when pure CoFe 2O 4 was used as catalyst; excellent results with turnover number of 288 and 92.4% selectivity for cyclohexanone and cyclohexanol was obtained under 1.6 MPa of initial oxygen pressure at 418 K after 6.0 h of reaction. The influences of initial oxygen pressure, reaction temperature, reaction time, and free-radical initiator on the oxidation of cyclohexane over CoFe 2O 4 were investigated. The catalyst can be easily separated by an external magnet and no obvious loss of activity was observed when reused in five consecutive runs. CoFe 2O 4 was proved to be also efficient for oxidation of linear alkanes.

Ionothermal Synthesis of Zirconium Phosphates and Their Catalytic Behavior in the Selective Oxidation of Cyclohexane

On their best behavior: Three zirconium compounds with one-, two-, and three-dimensional structures have been successfully synthesized by the ionothermal approach. The 3D zirconium phosphate (see picture; F green, H white, O red, P pink, Zr yellow) exhibits high catalytic performance, with a cyclohexane conversion ratio of 32% and cyclohexanone selectivity of up to 83%.

Cyclohexane oxidation catalyzed by manganese oxide octahedral molecular sieves—Effect of acidity of the catalyst

Oxidation of cyclohexane is an important industrial process, its oxidation products, cyclohexanol and cyclohexanone are raw materials for adipic acid and caprolactam synthesis. Acid exchanged cryptomelane type manganese oxide octahedral molecular sieves (H-K-OMS-2) was used for liquid phase oxidation of cyclohexane with t-butyl hydroperoxide as an oxidant. The H + form of K-OMS-2 was synthesized by ion-exchange of K-OMS-2 with concentrated nitric acid. H-K-OMS-2 has been found to be an efficient catalyst for the oxidation of cyclohexane with a high conversion (∼60%). More than 90% selectivity for cyclohexanol and cyclohexanone was obtained. A turn over number (TON) of 73 was obtained in 24 h at 80 °C and if we consider only contributions of acidic manganese sites then the TON is 287. Effect of increase in number of acid sites of the K-OMS-2 was correlated with the increase in conversion. The reactions were carried out in a semi-batch reactor at 80 °C using acetonitrile as solvent. Effects of solvent, temperature, and amount of t-butyl hydroperoxide on conversion and selectivity were studied.

Selective aerobic oxidation of cyclohexane catalyzed by metallodeuteroporphyrin-IX-dimethylester

Metallodeuteroporphyrin-IX-dimethylesters of Cu(II), Co(II), Ni(II) and Zn(II) were used successfully for the first time to catalyze the aerobic oxidation of cyclohexane without any co-catalysts and solvents. The reaction was carried out at 150 °C under 0.8 MPa and all the four metallodeuteroporphyrins acted as efficient catalysts. Among them, deuteroporphyrin-IX-dimethylester Co(II) had the best catalytic activity with enhanced cyclohexane conversion of 18.6%, selectivity of cyclohexanol and cyclohexanone of 84.6% and cyclohexane turnover number of 8.5 × 104. The cyclohexane conversion and catalysis turnover number for deuteroporphyrin-IX-dimethylester Co(II) were about 10 times of those for tetraphenylporphyrin Co(II), respectively.

Oxidation of Cyclohexane Catalyzed by TS-1 in Ionic Liquid with Tert-butyl-hydroperoxide

An efficient and environmentally friendly procedure was described for easy product isolation for the oxidation of cyclohexane with tert-butyl-hydroperoxide catalyzed by titanium silicalite 1 (TS-1) in ambient-temperature ionic liquid [emim]BF 4. Good yield and higher selectivity of products were found in the ionic liquid compared with in molecular solvent. The research results showed 13.2% conversion of cyclohexane, 97.6% cyclohexanol and cyclohexanone selectivity were obtained in ionic liquid under mild conditions of 90°C.

Selective Oxidation of Cyclohexane to Cyclohexanone Catalyzed by Phenanthroline–CuCl2 Complex

A highly efficient oxidation of cyclohexane to cyclohexanone is accomplished over phenanthroline–CuCl2 catalyst in relatively mild conditions. This study realized nearly 100% selectivity for cyclohexanone at 24.4% conversion of cyclohexane. The reaction has been studied by various parameters like performance of copper(II) salts, effect of solvents, influence of bases, the ratio of o-phenanthroline: CuCl2, and reaction time. In order to further study this reaction system, the possible mechanism was proposed.

Oxidative conversion of cyclohexane in discharge plasma maintained with different high-voltage power sources

The influence of the pulse parameters of supply voltage in a barrier discharge reactor on the yield of incomplete oxidation of cyclohexane was studied. It was shown that the voltage pulse parameters have an insignificant effect on both the product composition of cyclohexane oxidation and on selectivity for the products cyclohexanone (40.8%), cyclohexanol (49.5%), and water (9.7%). The lowest power consumption for the conversion of cyclohexane was achieved with the use of a sine wave generator operating at a frequency of 50 Hz (3.0 kWh kg−1) and a harmonic generator with a pulse duration of 15.3 μs and a pulse repetition frequency of 980 Hz (3.5 kWh kg−1). The space mode of barrier discharge was realized with the use of a generator of microsecond (53 μs) alternating voltage pulses.

Rational oxidation of cyclohexane to cyclohexanol, cyclohexanone and adipic acid with air over metalloporphyrin and cobalt salt

A systematic study on the effect of a catalyst on the aerobic oxidation of cyclohexane was carried out using cobalt isooctanoate, metalloporphyrin p- ClTPPCo and [p- ClTPPFe ]2 O as catalysts. The results showed that the metalloporphyrin-catalyzed system performed better than the traditional cobalt salt ( Co isooctanoate) in terms of both the reaction conversion and the selectivity of cyclohexanol and cyclohexanone (KA oil). More importantly, we discovered that bisironporphyrin complex, which was traditionally considered to be either non-active or not-so-active for hydrocarbon oxidation, excelled at 155°C, achieving high selectivity for KA oil (80%) and good reaction conversion (13.8%). This result is in sharp contrast to earlier results by others. Meanwhile, the production of adipic acid was also increased and good selectivity of adipic acid among the by-products was also obtained. Our study suggested that [p- ClTPPFe ]2 O catalyzed aerobic oxidation could be used to produce adipic acid in addition to KA oil. Some mechanistic rationales were proposed to explain the superior performance of the [p- ClTPPFe ]2 O catalyst based on its unique structural and chemical properties.

Liquid-phase selective hydrogenation of phenol to cyclohexanone over the Ce-doped Pd–B amorphous alloy catalyst

Ce-doped Pd–B amorphous alloy catalysts were prepared by chemical reduction of mixed PdCl 2 and Ce(NO 3) 3 with KBH 4. During liquid-phase selective hydrogenation of phenol to cyclohexanone, the as-prepared Pd–Ce–B catalysts exhibited much higher activity, better selectivity and excellent durability than the undoped Pd–B. Based on various characterizations, the promoting effect of Ce-dopant on the catalytic properties can be addressed as follows: (1) stabilizing the amorphous structure of Pd–B alloy and enhancing the dispersion degree of Pd active sites; (2) increasing the electron density of Pd, which could enhance hydrogenation activity and improve catalytic durability; (3) increasing the surface basicity, which facilitated the non-planar adsorption of phenol on catalyst surface, leading to higher cyclohexanone selectivity.