Direct Synthesis Of Phenol Research Articles

Liquid phase hydroxylation of benzene to phenol over Cu/ZnO catalysts

Liquid phase hydroxylation of benzene to phenol using Cu/ZnO catalysts prepared by the polyol process was investigated in aqueous acetic acid (20/80, v/v). Gaseous oxygen and ascorbic acid were utilized as the oxidant and reducing agent, respectively. The results showed that there is an optimum copper content over zinc oxide support. Phenol was the sole product of the oxidation reaction. No other product in the liquid phase was detected by gas chromatography and mass spectroscopy. Cu/ZnO catalysts prepared by the polyol process were found to be highly effective catalysts for direct phenol synthesis in the liquid phase. A major disadvantage of this system was that Cu/ZnO catalysts suffered from dissolution in the reaction medium. Cu/ZnO catalysts prepared by the polyol reduction showed comparatively higher activities.

ChemInform Abstract: Palladium-Catalyzed Transformation of Benzene to Phenol with Molecular Oxygen.

Very high turnover numbers of the catalyst in direct phenol synthesis from benzene have been attained using palladium catalyst, to give 25% yield of phenol based on the starting benzene.

In situ time-resolved DXAFS for the determination of kinetics of structural changes of H-ZSM-5-supported active Re-cluster catalyst in the direct phenol synthesis from benzene and O2

Dynamic structural changes and their kinetics of a Re(10)-cluster catalyst in the direct phenol synthesis from benzene and O(2) were investigated by in situ time-resolved Re L(III)-edge energy-dispersive XAFS (DXAFS). We have successfully monitored the structural transformation of active Re(10) clusters to inactive Re monomers in the course of the selective oxidation of benzene with O(2) on the catalyst by the DXAFS technique in a real time. The results obtained suggested that the Re(10) cluster transformed directly to the Re monomers, which showed first order kinetics with respect to the quantity of Re(10) clusters. The absence of undesirable intermediate structures with low phenol selectivity during the structural transformation may be an advantageous issue for the high phenol selectivity of 93.9% at 9.9% conversion in a pulse reaction and 87.7% at 5.8% conversion in a steady-state reaction on the Re(10)-cluster catalyst. The reactant benzene inhibited the unfavorable structural transformation of the Re(10) cluster to the Re monomers during the selective benzene oxidation to phenol.

ChemInform Abstract: Direct Phenol Synthesis from Benzene and Oxygen on Supported Rhenium Catalysts

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Density Functional Theory Study on the Re Cluster/HZSM-5 Catalysis for Direct Phenol Synthesis from Benzene and Molecular Oxygen: Active Re Structure and Reaction Mechanism

DFT calculations have been achieved to obtain a convincing model for the active structure in a Re cluster/HZSM-5 catalyst active for direct phenol synthesis from benzene and molecular oxygen. Re10 clusters with interstitial N atoms composed of two Re octahedra edge-shared with each other were concluded as a stable active structure in agreement with the EXAFS analysis. The adsorption and behavior of benzene, oxygen atom and molecule and phenol on the Re cluster were examined to obtain the energy diagram for the phenol synthesis including intermediate and transition states, which explains the reaction steps for the phenol synthesis.

担持Ｒｅ触媒を用いたベンゼンと酸素からのフェノールの直接合成反応

Phenol is one of the most important chemicals in industry and it is produced from cumene process from benzene. Direct phenol synthesis from benzene and O2 is an alternative way to produce phenol efficiently. We have succeeded in preparing a HZSM-5-zeolite-supported Re catalyst, which was highly active and selective for direct phenol synthesis from benzene and O2 (steady-state reaction: 5.8% benzene conversion and 88% phenol selectivity, pulse reaction: 9.9% benzene conversion and 94% phenol selectivity) in the presence of NH3. The formation of active Re clusters, their structural change, and the role of NH3 which are relevant to the selective benzene oxidation were investigated.

Palladium‐Catalyzed Coupling of Ammonia and Hydroxide with Aryl Halides: The Direct Synthesis of Primary Anilines and Phenols

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Novel Re-Cluster/HZSM-5 Catalyst for Highly Selective Phenol Synthesis from Benzene and O2: Performance and Reaction Mechanism

This paper reports the catalytically active structure, its structural transformation and dynamics, and the reaction mechanism for direct phenol synthesis from benzene and molecular oxygen on a novel N-interstitial Re10-cluster/HZSM-5 catalyst, which exhibited remarkable phenol selectivities of 91.6−93.9% at 1.7−9.9% conversions in pulse reactions and 82.4−87.7% at 0.8−5.8% conversions in steady-state reactions. The active N-interstitial Re10 cluster for the direct phenol synthesis with O2 as an oxidant was produced by NH3 at 553 K and the phenol synthesis proceeded with the low activation energy of 24 kJ mol-1. The active Re10 cluster was converted to inactive Re monomers, while NH3 reproduced the active Re10 cluster under the reaction conditions. It was found by means of in situ time-resolved XAFS and DFT calculations that the catalytic phenol synthesis proceeded in conjunction with the structural transformation between the Re10 clusters and the Re monomers. The isosbestic points in energy-dispersive XANES spectra indicated a direct conversion of the Re10 cluster to the Re monomers without any unfavorable metastable intermediates. The benzene oxidation is proposed to proceed via oxygen addition to a C atom of benzene to form an oxygen-added intermediate with a sp3 carbon atom in the benzene ring and subsequent insertion of the oxygen to the C−H bond on the Re10 cluster.

One-Step Hydroxylation of Benzene to Phenol Induced by Glow Discharge Plasma in an Aqueous Solution

Direct phenol synthesis from benzene in aqueous solution where water was used as the oxidant through glow discharge plasma (GDP) process was described for the first time. The effect of pH, ferrous and cupric ions on the phenol yield and selectivity was examined. Phenol yield of 8.3% and selectivity of 81% has been achieved.

Palladium‐Catalyzed Coupling of Ammonia and Hydroxide with Aryl Halides: The Direct Synthesis of Primary Anilines and Phenols

Palladium‐Catalyzed Coupling of Ammonia and Hydroxide with Aryl Halides: The Direct Synthesis of Primary Anilines and Phenols

Palladium-catalyzed C–O bond formation: direct synthesis of phenols and aryl/alkyl ethers from activated aryl halides

A simple and efficient palladium-catalyzed carbon–oxygen bond formation is reported. The palladium-tri- tert-butylphosphine complex was found to be effective in converting haloarenes to corresponding substituted phenols. This methodology offers a direct transformation of aryl halides to phenols, as well as the straightforward application to generate a wide variety of diaryl or alkyl/aryl ethers.

The Selective Reaction of Aryl Halides with KOH: Synthesis of Phenols, Aromatic Ethers, and Benzofurans

The direct and selective synthesis of phenols from aryl/heteroaryl halides and KOH has been achieved through the use of highly active monophosphine-based catalysts derived from Pd(2)dba(3) and ligands L1 or L2 and the biphasic solvent system 1,4-dioxane/H(2)O. We have also demonstrated a one-pot method of phenol formation/alkylation for the preparation of alkyl aryl ethers from aryl halides. In many instances, this protocol overcomes limitations in existing Pd-catalyzed coupling reactions of aliphatic alcohols with aryl halides. Finally, we demonstrate that substituted benzofurans can be prepared efficiently via a Pd-catalyzed phenol formation/cyclization protocol starting from 2-chloroaryl alkynes.

Catalyst design for selective oxidation with molecular oxygen by metal-complex attachment

We have prepared novel metal-ensemble catalysts by chemical attachment of metal-complex precursors, N-interstitial Re 10 cluster supported on HZSM-5 and chiral self-dimerized V-dimer on SiO 2, which are active and highly selective for selective oxidation with molecular oxygen. The Re 10(N) 2/HZSM-5 catalyst exhibited 87.7% (steady-state reaction) and 93.9% (pulse reaction) selectivity for direct phenol synthesis from benzene with molecular oxygen. The structures of active metal species were characterized by EXAFS, TPD and DFT calculations. The chiral self-dimerized V-dimer catalyst was found to be the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol with molecular oxygen, which exhibited 100% selectivity and 90% enantioselectivity.

Direct Oxidation of Benzene to Phenol Catalyzed by Vanadium Substituted Heteropolymolybdic Acid

Direct synthesis of phenol by hydroxylation of benzene with H2O2 over the vanadium-substituted heteropolymolybdic acid catalyst was investigated at 70 °C. H2O2 was used as an oxidant while 36 wt.% MeCO2H was employed as the solvent. After 100 min the selectivity for phenol was 93% and the yield of PhOH was 10.1%. The catalyst was characterized by elemental analysis, thermal gravimetric analysis, infrared spectroscopy, u.v.–vis spectroscopy, X-ray diffraction, and 31P-n.m.r. and 51V-n.m.r. techniques. The experimental conditions such as reaction temperature, the amounts of H2O2 and catalyst were explored. The as-prepared phenol could be separated by column chromatography and was characterized by infrared and mass spectrometry.

Direct Phenol Synthesis by Selective Oxidation of Benzene with Molecular Oxygen on an Interstitial-N/Re Cluster/Zeolite Catalyst

Direct Phenol Synthesis by Selective Oxidation of Benzene with Molecular Oxygen on an Interstitial-N/Re Cluster/Zeolite Catalyst

Direct Phenol Synthesis by Selective Oxidation of Benzene with Molecular Oxygen on an Interstitial‐N/Re Cluster/Zeolite Catalyst

Direct Phenol Synthesis by Selective Oxidation of Benzene with Molecular Oxygen on an Interstitial‐N/Re Cluster/Zeolite Catalyst

Direct oxidation of benzene to phenol catalyzed by a vanadium-substituted heteropolymolybdic acid catalyst

The direct synthesis of phenol by hydroxylation of benzene with hydrogen peroxide over a vanadium substituted heteropolymolybdic acid catalyst was investigated at 70 ?C. Hydrogen peroxide was used as the oxidant while 36 wt.% acetic acid was employed as the solvent. After 100 minutes, the selectivity for phenol was 93% and the yield of phenol was 10.1 %. The catalyst was characterized by elemental analysis, thermogravimetry, infrared spectroscopy, UV-Vis spectroscopy, X-ray diffraction, and 31P-NMR and 51V-NMR techniques. The experimental conditions, such as reaction temperature, the amount of hydrogen peroxide and catalyst, were investigated. The as-prepared phenol could be separated by column chromatography and was characterized by infrared and mass spectrometry.

Direct synthesis of phenol from benzene on iron-impregnated activated carbon catalysts

The direct conversion of benzene to phenol by hydroxylation with hydrogen peroxide was carried out over catalysts containing iron impregnated on activated carbon. Iron was impregnated on various surface modified activated carbons. The catalyst that was made by treating activated carbon with nitric acid, that was treated thermally in the presence of nitrogen at 600 °C and impregnated with 5 wt.% iron, gave a phenol yield of 20%. It was found that the synergistic interactions of surface groups and the impregnated iron have enhanced the performance of these catalysts.

Photocatalytic conversion of benzene to phenol using modified TiO 2 and polyoxometalates

The application of photocatalytic reactions to organic synthesis has attracted interests in view of the development of environmentally benign synthetic processes. This study investigated the effects of various parameters (electron acceptor, surface modification, and the combination of photocatalysts) on the direct synthesis of phenol from benzene using photocatalytic oxidation processes. The OH radicals generated on UV-illuminated TiO 2 photocatalyst directly hydroxylate benzene to produce phenol, hydroquinone, and catechol. The addition of Fe 3+, H 2O 2, or Fe 3+ + H 2O 2 highly enhanced the phenol production yield and selectivity in TiO 2 suspension. Surface modifications of TiO 2 had significant influence on the phenol synthetic reaction. Depositing Pt nanoparticles on TiO 2 (Pt/TiO 2) markedly enhanced the yield and selectivity. Surface fluorination of TiO 2 (F-TiO 2) increased the phenol yield two-fold because of the enhanced production of mobile (free) OH radicals on F-TiO 2. Polyoxometalate (POM) in phenol synthesis played the dual role both as a homogeneous photocatalyst and as a reversible electron acceptor in TiO 2 suspension. POM alone was as efficient as TiO 2 alone in the phenol production. In particular, the addition of POM to the TiO 2 suspension increased the phenol yield from 2.6% to 11% (the highest yield obtained in this study). Reaction mechanisms for each photocatalytic system were discussed in relation to the phenol synthesis.

One-step synthesis of phenol by O– and OH– emission material

A novel approach to the direct synthesis of phenol from benzene was obtained with high benzene conversion (30%) and phenol selectivity (approximately 90%) by using a microporous material [Ca24Al28O64]4+.4O-(C12A7-O-) as catalyst with oxygen and water; active O- and OH- anions are proposed to play important roles in the formation of phenol by hydroxylating the aromatic ring of benzene.