Hydroxylation Of Phenol Research Articles

Hydroxylation of phenol with H2O2 over binary Cu–Pd–alginate catalyst in the fixed-bed flow reactor

A series of Cu–alginate and Cu–Pd–alginate catalysts were prepared by the ion exchange of Na–alginate, and their structures were well characterized by FT-IR, XPS and ICP-AES measurements. Their catalytic activities for phenol hydroxylation in the fixed-bed flow reactor were investigated. The effects of different reaction conditions, such as molar ratio of phenol/H2O2, reaction temperature, weight hourly space velocity, solution and weight ratio of water/phenol were evaluated. Under the optimum reaction conditions, 17.1 % phenol conversion was obtained with selectivities to catechol and hydroquinone being 67.7 and 31.4 %, respectively. The 16.0–18.0 % phenol conversion and selectivities to HQ 30.0–32.0 %, CAT 66.0–68.0 % and BQ 0.7–2.0 % of the long-run catalytic test confirmed the excellent stable catalytic activity of the catalyst.

Hydrothermal synthesis and characterization of aluminum-free Mn-β zeolite: a catalyst for phenol hydroxylation.

Zeolite beta, especially heteroatomic zeolite beta, has been widely used in the industries of fine chemicals and petroleum refining because of its outstanding thermal stability, acid resistance, and unique 3-D open-frame structure. In this paper, aluminum-free Mn-β zeolite was hydrothermally synthesized in the SiO2-MnO2-(TEA)2O-NaF-H2O system. The effect of the chemical composition of the precursor mixture to the crystallization of the Al-free Mn-β zeolite was investigated. The synthesized Al-free Mn-β zeolite was characterized by inductively coupled plasma (ICP), XRD, thermogravimetric/differential thermal analysis (TG/DTA), N2 adsorption-desorption, FT-IR, UV-vis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The results show that the synthesized zeolite has a structure of β zeolite with good crystallinity and Mn ions present in the framework of the zeolite. The synthesized Al-free Mn-β zeolite shows great catalytic activity toward the phenol hydroxylation reaction using H2O2 as the oxidant. Approximately 35% of phenol conversion and ∼98% of dihydroxybenzene selectivity can be obtained under the optimal conditions.

Hydroxylation of Phenol on Iron-Containing Mesoporous Silica with Hierarchical Macroporous Architecture

Abstract Iron-containing mesoporous silica with hierarchical macroporous architecture (Fe-MMS) was prepared by applying a solvent evaporation method. In the hydroxylation of phenol with H2O2, the advantageous structure of Fe-MMS realized the higher selectivity for formation of dihydroxybenzene (catechol and hydroquinone) as compared to Fe-containing mesoporous silica (Fe-MS).

Preparation of Fe/activated carbon directly from rice husk pyrolytic carbon and its application in catalytic hydroxylation of phenol

The loading of iron and the formation of activated carbon were combined to one step and the thus-obtained Fe/activated carbon showed good catalytic performance for phenol hydroxylation.

The preparation of Fe/wood-based activated carbon catalyst for phenol hydroxylation from Fe2+ and Fe3+ precursors

Loading of Fe3+ and Fe2+ on wood-based activated carbon obtained Fe-based catalyst with good catalytic performance for phenol hydroxylation.

Catalytic Hydroxylation of Phenols using Schiff base complex of Copper metal complexes derived from L-histidine

A new Schiff base metal complex of quinoxiline 2-carboxyaldehyde and L-histidine was prepared. The resulting complex was analyzed through different physiochemical techniques like elemental analysis, molar conductivity measurement ,Thermo gravimetry and differential gravimetry technique, FT-IR, EPR spectrum etc. The catalytic application of the complex was checked in liquid phase hydroxylation of phenols. The effect of different physical and chemical parameters like effect of catalyst amount and oxidant ,effect temperature were also recorded. It was found the catalyst is suitable for caring out the liquid phase oxidation of phenols. The catalyst gives more than 40% oxidation product conversion.

Mechanistic Insights into Phenol Oxidation by a Copper(II) Complex of a Pyridine‐ and Amide‐Containing Copolymer in an Aqueous Medium

A CuII complex of a pyridine- and amide-containing copolymer (Cu-P1) exhibits effective activity toward phenol hydroxylation in 50 % aqueous methanol solution at apparent pH 8.0 and 25 °C. The complex shows significant first-order rate accelerations of 4.2 × 105 and 1.4 × 105 relative to phenol autoxidation in air and in the presence of 20 mM H2O2, respectively. The reaction mechanisms with H2O2 and air are different on the basis of (a) the different activity profiles for Cu binding, (b) the different deuterium kinetic isotope effects (2.8 in 20 mM H2O2 and 1.2 aerobically), and (c) the formation of a dinuclear substrate–(Cu-P1) complex with H2O2 but a mononuclear one aerobically. The mechanism in the presence of H2O2 is consistent with that of the type-3 dicopper tyrosinase. Although oxidized di-CuII tyrosinase can only use H2O2 for phenol hydroxylation, CuII-P1 can use either air or H2O2 for this process. The studies herein introduce a versatile chemical system for the further exploration of Cu–oxygen chemistry and other types of metal-centered chemistry and for the aerobic degradation of aromatic compounds in environmental and green chemistry.

Impressivephenol hydroxylation activity using Fe–Ti-TUD-1 synthesized from silatrane via sol–gel process

Bimetallic Fe–Ti-TUD-1 three-dimensional amorphous mesoporous materials were successfully synthesized via sol–gel method, using tetraethylammonium hydroxide (TEAOH) as a structural directing agent; silatrane, FeCl3, and Ti(OCH(CH3)2)4 as silica, iron, and titanium sources, respectively. The obtained Fe–Ti-TUD-1 has a foam-like mesoporous structure with surface area ranging from 625 to 725m2/g, an average pore size of 6nm, and a pore volume of0.97cm2/g. The phenol hydroxylation of the samples was evacuated using H2O2 as the oxidant and water as the medium. The effects of influence parameters, such as temperature, reaction time, catalyst amount, amount of oxidant, and metal loading, were investigated; the optimum condition was found to be a ratio of 1:3 phenol:H2O2, using 30mg of catalyst at 363K for 1h. For comparison, photocatalysisfor phenol hydroxylation was studied at room temperature. The result revealed that the activity of 0.01Ti-TUD-1 was improved under UV radiation, but the overall activity resulted in lower performance than the reaction under heat. Phenol hydroxylation using 0.01Fe–0.01Ti-TUD-1 gave 93.1% conversion at 363K with 53.4% hydroquinone (HQ) and 46.6% catechol (CAT) selectivity. As Fe incorporated into the structure, it improved the catalytic ability of Ti-TUD-1. Unfortunately, the activity of Fe dropped under the UV light since iron species were less active in this condition.

Synthesis and Characterization of Heteroatomic Ti-Mn-β Zeolite and Its Catalytic Performance on Phenol Hydroxylation

采用水热合成法在Si O2-Ti O2-Mn O2-（TEA）2O-H2O-NH4F体系中合成了Ti-Mn-β沸石。运用X射线衍射、红外光谱、固体紫外可见漫反射、热重-差热、扫描电子显微镜和X射线光电子能谱等技术手段对样品进行了表征,探讨了影响Ti-Mn-β沸石合成的因素。Ti-Mn-β沸石在以H2O2为氧化剂的苯酚羟基化反应中表现出较好的催化活性,苯酚的转化率为29.8%,邻苯二酚和对苯二酚的选择性分别为70.9%和26%。

High Catalytic Activity in the Phenol Hydroxylation of Magnetically Separable CuFe2O4–Reduced Graphene Oxide

We reported a highly active CuFe2O4 catalyst modified with reduced graphene oxide (CuFe2O4–RGO) by a solvothermal method. The composite catalyst was fully characterized by FTIR, XRD, Raman, TEM, and XPS, which demonstrated that the CuFe2O4 nanoparticles (NPs) with a diameter of approximately 17.8 nm were densely and compactly deposited on the reduced graphene oxide (RGO) sheets. The as-prepared CuFe2O4–RGO composites were used to catalyze phenol hydroxylation for the first time, which exhibited great catalytic activity. The conversion rate of phenol to dihydroxybenzenes reached 35.5% with a selectivity of 95.2% obtained, which is much higher than for reported systems (25.0%). The catalytic activity remained high after six cycles. More importantly, the catalyst can be easily recovered due to its magnetic separability and the organic solvent-free nature of the phenol hydroxylation process. A possible mechanism in phenol hydroxylation by H2O2 over CuFe2O4–RGO20 catalyst was also proposed.

Catalytic properties of Fe-HMS materials in the phenol oxidation

Iron-incorporated mesoporous silica material Fe-HMS-50 (the Si/Fe molar ratio in the precursor gel is 50) was synthesized at ambient temperature by using hexadecylamine as a template and characterized by chemical analysis and N2 adsorption measurements. The catalytic performance of Fe-HMS was studied in the phenol hydroxylation and wet phenol oxidation with H2O2 at 313 K. The effect of pH, H2O2: PhOH molar ratio and stability of the catalyst on the oxidation process was investigated. In the phenol oxidation, the activity of the catalyst increases by increasing the acidity of the reaction mixture to pH 3.4 and the amount of leached iron species was 1.95 ppm. A recycling test indicates that the catalyst recovered by drying in air at 423 K suffered, after the first run, a 12.4% drop in the catalytic activity. Fe-HMS has high catalytic activity and selectivity to dihydroxybenzene in the phenol hydroxylation. Hydroquinone was found as the predominant product under these experimental conditions with small amounts of benzoquinone appearing at the end of the reaction.

Synthesis and Catalytic Activity of Fe-MCM-41 Nanoparticles

Mesostructured Fe-MCM-41 nanoparticles have been hydrothermally prepared for the first time with assistance of binary surfactants (CTAB and F127). The formation of nanoparticles consists of two steps, that is, the hydrolysis of silica precursor via catalysis by an acidic ferric salt, followed by facile assembly into mesostructured nanocomposites with cationic micelles by addition of condensation catalyst. In the hydroxylation of phenol with aqueous H2O2, Fe-MCM-41-NP displayed higher activity than a Fe-MCM-41 sample with normal particle size (Fe-MCM-41-LP).

Liquid-phase catalytic hydroxylation of phenol using metal crosslinked alginate catalysts with hydrogen peroxide as an oxidant

A series of divalent metal (Cu, Co, Ni, Fe, Mn, Zn and Pd) crosslinked alginate dry beads catalysts were prepared using metal chloride and sodium alginate. The resulting catalysts were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy, energy-dispersive X-ray analyses and nitrogen physisorption measurements. The characterization results showed that a series of ion-crosslinked metal-alginate dry beads were synthesized through ion exchange, followed by the coordination of alginate and metal ions. These materials have been assessed as catalysts for liquid-phase hydroxylation of phenol to dihydroxybenzenes using H2O2 as an oxidant. The results showed that Cu-based catalyst exhibited higher activity than other metal-based catalysts for phenol hydroxylation. The influence of key reaction parameters, including the reaction temperature, solvent, reaction time, initial pH, molar ratio of phenol/H2O2 and the amount of catalyst on the reactivity and selectivity were also investigated. Finally, the reusability of Cu-based catalyst illustrated that it could be recovered and reused without notable loss of activity.

Influence of TiO2/TS-1 Calcination on Hydroxylation of Phenol

Titanium oxide (TiO2) was impregnated on the surface of titanosilicate-1 (TiO2/TS-1) and used as catalyst for hydroxylation of phenol with hydrogen peroxide. Calcination was conducted at various temperatures (400, 500, 600 and 700°C)in order to observe the effect on the structure and physicochemical properties towards catalytic activity for producing hydroquinone. The structure and physicochemical properties of the TiO2/TS-1 catalyst were characterized by several techniques, such as X-ray diffraction (XRD), infrared spectroscopy, nitrogen adsorption, pyridine adsorption and hydrophilic measurement. The results show that by increasing the calcination temperature,the surface acidity of the catalyst was also increased.TheTiO2/TS-1 catalyst calcined at 500°Cproved to be optimal for hydroquinone production, in which the anatase-rutile phase may be present dispersed on the MFI framework.

Synthesis of a Fe–MFI zeolite with super-micropores by using potassium hexacyanoferrate(III) as an iron source

Zeolite Fe–MFI possessing super-micropores has been synthesized by a direct hydrothermal method using potassium hexacyanoferrate(III) as the iron source. The results show that the material has a highly crystalline MFI zeolite structure, displaying a regular structure with ca. 0.7–1.5nm in pore diameter. X-ray absorption spectroscopy results indicated that the iron was present in the form of tetrahedrally coordinated Fe3+ ions incorporated on the zeolite network. The super-microporous Fe–MFI exhibited good catalytic performance in the hydroxylation of phenol by H2O2.

Catalytic activity of supported solid catalysts for phenol hydroxylation

Cobalt(II), copper(II) and zinc(II) complexes of 2-phenylbenzimidazole (PhBzlH) encapsulated in the supercages of zeolite-Y and ZSM-5 have been synthesized and characterized by spectroscopic studies (IR, UV/visible, EPR), elemental analyses, thermal studies and X-ray diffraction patterns. The catalytic activity of encapsulated complexes was investigated for the hydroxylation of phenol using 30 % H2O2 as an oxidant. Under optimized reaction conditions, the hydroxylation of phenol yielded catechol and hydroquinone as the major products. All catalysts show good selectivity for diphenol products. A maximum conversion of phenol was obtained with [Cu(PhBzlH)]-Y as the catalyst. The results showed that conversion of phenol varies in the order [Cu(PhBzlH)]-Y (53 %) > [Cu(PhBzlH)]-ZSM-5 > (49 %) > [Co(PhBzlH)]-ZSM-5 (47 %) > [Co(PhBzlH)]-Y (46 %) > [Zn(PhBzlH)]-Y (45 %) > [Zn(PhBzlH)]-ZSM-5 (41 %) after 6 h of reaction time. Test for the recyclability of the reaction was also carried out and the results indicate their recyclability.

Application of Fe/Activated Carbon Catalysts in the Hydroxylation of Phenol to Dihydroxybenzenes

A series of Fe/activated carbon catalysts were prepared by impregnation of activated carbon with aqueous solution of ferric nitrate and employed in phenol hydroxylation to dihydroxybenzenes using hydrogen peroxide as oxidant. The samples were characterized by thermal analysis, inductively coupled plasma atomic emission spectrometry (ICP-AES), N2-adsorption, temperature-programmed oxidation mass spectrometry (TPO-MS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Part of the ferric (Fe(III)) species was reduced to ferrous (Fe(II)) species forming Fe3O4 when the Fe/activated carbon catalyst was heated at 400 °C for 3 h in air. Fe3O4 highly dispersed on activated carbon was found to be the active phase for the target reaction. The appearance of ferrous (Fe(II)) species greatly improved the catalytic activity. A phenol conversion of 41.3% and a yield of 36.0% to dihydroxybenzenes were obtained under the following optimal reaction conditions: catalyst ...

Preparation of a 2,2′-(4-nitrophenyl)dipyrromethane copper coordination compound and its catalytic behavior for phenol hydroxylation

With 2,2′-(4-nitrophenyl)dipyrromethane and copper acetate as raw materials, a 2,2′-(4-nitrophenyl)dipyrromethane copper coordination compound was successfully synthesized in methanol solution. The complex was characterized by Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, elemental analysis and mass spectrometry to evidence formation of the coordination binding between the pyrrole ring units and the copper ion. This complex was applied to catalyze phenol hydroxylation, and the key reaction parameters on the catalytic activity and selectivity were investigated. The study paves the way for exploring high efficient catalyst for phenol hydroxylation. After three catalytic runs, the copper complex also kept excellent activity.

Direct synthesis of hierarchically porous TS‐1 through a solvent‐evaporation route and its application as an oxidation catalyst

Synthesis of hierarchically porous zeolites has drawn intensive interest because of their improved catalytic performance. It is highly desirable to find ways to generate these materials in a low‐cost and scalable way for their commercial applications. A solvent evaporation route has been established to synthesize hierarchically porous titanosilicalite‐1 (TS‐1). In the protocol, hexadecyltrimethoxysilane was added to an ethanolic solution of titanium isopropoxide, tetraethyl orthosilicate and tetrapropylammonium hydroxide, i.e. the embryo solution of TS‐1. The solution was subjected to solvent evaporation‐induced self‐assembly to afford an ordered dry gel. Subsequent steam‐assisted crystallization converted the dry gel into a hierarchically porous TS‐1. X‐ray powder diffraction (XRD), UV–visible diffusive reflectance spectroscopy, N2 physisorption and electron microscopic characterizations have been employed to elucidate the structure. Ti is incorporated into the tetrahedral sites of the MFI structure and mesopores around 20 nm penetrating the crystalline framework are formed. Hexadecyltrimethoxysilane plays a key role in creating mesopores as well as increasing the crystal size. The hierarchically porous TS‐1 exhibits improved activity in styrene oxidation and phenol hydroxylation. Copyright © 2014 John Wiley & Sons, Ltd.

Synthesis of Micro-Sized MEL-Type Zeolite Aggregates

Hierarchical micro-sized zeolite aggregates with the MEL structure were prepared hydrothermally from a tetrabutylammonium hydroxide(TBAOH)-tetraethyl orthosilicate(TEOS)-H2O system. The obtained microsized silicalite-2 microspheres had sizes larger than 10 μm, high BET surface area(460 m2·g-1), and large pore volume(0.74 cm3·g-1). The formation of micro-sized spheres alleviates preparation and application difficulties.The presence of inter-crystalline mesopores originating from the spontaneous assembly of nano-sized primary particles during hydrothermal synthesis gives the advantages of nanoparticles, reducing diffusion limitations.The introduction of titanium does not strongly affect the morphology and textural properties of the MEL-type zeolite, which are quite similar to those of silicalite-2 aggregates. The micro-sized titanium silicalite-2(TS-2)microspheres showed comparable catalytic activity in phenol hydroxylation to that of titanium silicalite-1(TS-1) of size 100-200 nm, and were easily recovered by traditional filtration, simplifying the separation and recovery compared with nano-sized TS-1.