Hydroxylation Of Benzene Research Articles

Enhanced Hydroxylation of Benzene to Phenol with Hydrogen Peroxide over g-C3N4 Quantum Dots-Modified Fe-SBA-15 Catalysts: Synergistic Effect Among Fe Species, g-C3N4 QDs, and Porous Structure

g-C3N4 quantum dots (QDs) attract considerable attention due to its remarkable applications in various fields such as catalysis, ion detection, and biosensors. Herein, the inner surface of the hexagon channels of Fe-SBA-15 was adorned by g-C3N4 QDs to enhance direct hydroxylation of benzene with H2O2 to afford phenol. The crystal texture, porous properties, inner structure, morphology, elemental distribution, chemical composites, and bonding energy of the synthesized CN-QDs/Fe-SBA-15 were thoroughly analyzed and characterized using X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy (TEM), scanning electron microscopy–energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, high-angle annular dark-field scanning TEM, X-ray photoelectron spectroscopy, and UV–vis and Fourier-transform infrared spectroscopies. The catalytic performance of the synthesized g-C3N4 QD-decorated Fe-SBA-15 was explored for one-step direct oxidation of benzene, with H2O2 as a green oxidant to obtain phenol. The structural characterization and catalytic investigation revealed that benzene molecules were adsorbed on the surface of CN-QDs by noncovalent interactions and activated by the terminal groups, that is, N-defects/C–OH present on the edges of CN-QDs. Then, the activated benzene was attacked by the hydroxyl radical generated by iron-peroxo-capturing hydrogen ion to produce phenol. The mesoporous structure of Fe-SBA-15 not only deals with the stability and aggregation of g-C3N4 QDs but also ensures the uniform dispersion of Fe species on the inner surface of the channel. The maximum yield of phenol obtained was 41.2% in this catalytic system, which is crucially dependent on the synergic effect between g-C3N4 QDs and Fe-SBA-15.

Small-sized biomass-derived hydrothermal carbon with enriched oxygen groups quickens benzene hydroxylation to phenol with dioxygen

Metal-free carbon materials have attracted growing attention in terms of green and sustainable catalysis processes that could avoid potential metal leaching but usually suffered from inferior activity to metal-loaded counterparts. In this work, we constructed an efficient carbon catalyst via hydrothermal carbonization of biomass-derived feedstock glucose under relatively low temperature (180 °C). The resultant carbon material possessing abundant surface oxygen species effectively catalyzed the benzene hydroxylation with dioxygen (O2), a desirable but very difficult alternative process for producing the important bulk chemical phenol. A considerably high phenol yield of 13.1% was achieved within 4 h, a reaction time much shorter than all the previous metal-free catalysts and even shorter than most efficient metal-based catalysts. The fast reaction is determined by the formation of small-sized primary carbon particles with the abundant surface oxygen species, for which the adsorption enhancing effect in the media of this heterogeneous process was experimentally evidenced.

Synthesis TS-1 nanozelites via L-lysine assisted route for hydroxylation of Benzene

L-lysine is used as a crystallization regulator, and a two-step synthesis method is adopted in a concentrated gel system, which provides a new route to synthesize of nano-sized TS-1 zeolite. The new synthesis strategy was used to successfully synthesize TS-1 zeolite with a particle size less than 100 nm. The rate of crystal nucleation is faster than the crystal growth at the low temperature in the first step. Introduction of L-lysine can prevent crystal growth to form nano-sized TS-1 zeolite at the high temperature in the second step. Meanwhile, L-lysine decrease the pH value of the gel system, which is favorable for Ti atoms to incorporate the TS-1 framework. TS-1 nanozeolite can effectively reduce the diffusion resistance, and nanozeolite has a large specific surface area and high stability. Therefore, TS-1 nanozeolite exhibits the excellent catalytic performance during the hydroxylation of benzene. The conversion of benzene has been greatly improved and the types of by-products are effectively reduced. The conversion of benzene reached 50.2%, and the yield of phenol was 30.8% without by-product benzoquinone. TS-1 nano-zeolite as a catalyst for benzene hydroxylation shows great potential in industrial application.

Pilot-Scale Production of Peroxygenase from Agrocybe aegerita.

The pilot-scale production of the peroxygenase from Agrocybe aegerita (rAaeUPO) is demonstrated. In a fed-batch fermentation of the recombinant Pichia pastoris, the enzyme was secreted into the culture medium to a final concentration of 0.29 g L–1 corresponding to 735 g of the peroxygenase in 2500 L of the fermentation broth after 6 days. Due to nonoptimized downstream processing, only 170 g of the enzyme has been isolated. The preparative usefulness of the so-obtained enzyme preparation has been demonstrated at a semipreparative scale (100 mL) as an example of the stereoselective hydroxylation of ethyl benzene. Using an adjusted H2O2 feed rate, linear product formation was observed for 7 days, producing more than 5 g L–1 (R)-1-phenyl ethanol. The biocatalyst performed more than 340.000 catalytic turnovers (942 g of the product per gram of rAaeUPO).

Synergistic Effect between Fe and Cu Species on Mesoporous Silica for Hydroxylation of Benzene to Phenol

Synergistic Effect between Fe and Cu Species on Mesoporous Silica for Hydroxylation of Benzene to Phenol

Homogeneous oxidative transformations mediated by copper catalyst systems

• State of the art copper-catalysed oxidative transformations is described. • Oxidation and oxygenation, peroxidation and hydroxylation reactions are reviewed. • Key differences in the mechanistic pathways are discussed. Oxidative transformations involve the conversion of organic substrates, through various processes to obtain oxygenates such as alcohols, phenolic and carbonyl compounds which can be used in the pharmaceutical and chemistry industries. Inspired by nature, particularly copper-based enzymes, these reactions include, but are not exclusive to, the radical co-catalyst free oxidation of activated alcohols inspired by copper-based oxidases, the hydroxylation of monophenols which is inspired by tyrosinase, the hydroxylation of benzene, peroxidation of hydrocarbons and oxidative cleavage of polysaccharide model substrates, which draws inspiration from oxygenases. Copper, as an environmentally benign metal pre-catalyst, has received considerable attention during the development of various catalyst systems to generate oxygenates. The mechanistic pathways by which these Cu-based catalyst systems operate has been investigated extensively and the major differences involve the initial oxidation state of copper, the redox lability of these oxidation states and the nature of the Cu-based active species. Herein we provide critical review of developments in copper-catalysed oxidative transformations.

Mechanistic Insights into the Dicopper-Complex-Catalyzed Hydroxylation of Methane and Benzene Using Nitric Oxide: A DFT Study.

Although hydrocarbons are known to act as reductants for the catalytic reduction of nitric oxides (NOx) over copper-based catalysts, the reaction mechanism requires clarification. Herein, density functional theory (DFT) calculations were carried out to investigate the reduction mechanisms of NOx to dinitrogen coupled to the hydroxylation of methane or benzene using the dicopper complex reported by Zhang and co-workers [ J. Am. Chem. Soc. 2019, 141, 10159-10164]. The B3LYP functional was used to optimize the (μ-oxo)(μ-nitrosyl)dicopper complex in the quartet state and the (μ-η2:η2-NO2)dicopper complex in the doublet state, the latter of which was found to be the ground state. Then, we investigated the reactivities of the (μ-η2:η2-NO2)dicopper complex toward methane and benzene by considering the conversions of N2O to N2 in the presence and the absence of methane or benzene. In the presence of methane and benzene, the calculated activation energies were 27.0 and 21.0 kcal/mol, respectively, whereas that with N2O alone was prohibitively high (61.9 kcal/mol). Thus, the (μ-η2:η2-NO2)dicopper complex prefers the reactions with methane and benzene to that with N2O. The reaction of the (μ-η2:η2-NO2)dicopper complex with methane or benzene generated the (μ-nitrosyl)dicopper complex. The (μ-nitrosyl)dicopper complex then reacted with N2O to regenerate the (μ-η2:η2-NO2)dicopper complex and N2 with an activation barrier of 31.5 kcal/mol. The overall reactions for methane and benzene hydroxylation were calculated to be exothermic by 41.7 and 54.1 kcal/mol, respectively. These results suggest that the catalytic reduction of NOx using hydrocarbons is feasible at certain operating temperatures. Thus, our calculations provide new insights into the design of catalysts for NOx purification.

Enhancement of Catalytic Activity for Benzene Hydroxylation over Novel V2O5/HZSM-5 Catalyst

Enhancement of Catalytic Activity for Benzene Hydroxylation over Novel V2O5/HZSM-5 Catalyst

One-pot synthesis of highly active Fe-containing MWW zeolite catalyst: Elucidation of Fe species and its impact on catalytic performance

Fe-containing MWW zeolite catalysts in the absence (Fe-MWW) or presence of Al atoms (Fe,Al-MWW) were directly prepared by the hydrothermal synthesis approach. The nature of Fe species was systematically analyzed by UV–vis, in-situ NO adsorption FTIR spectroscopy, and H2-TPR technology. The presence of Al atoms in the synthesis gel seriously affected the chemical composition, textural properties, and the states of Fe species, hence made the catalytic activity in hydroxylation of benzene with H2O2 worse than the one without Al. Moreover, we found that the states of Fe species could be adjusted by changing the calcination temperature. The catalytic activity of Fe-MWW was improved by increasing the calcination temperature, while that of Fe,Al-MWW was weakened due to the degeneration of texture properties and the transformation of Fe species. Fe-MWW zeolite calcined at 750 °C exhibited the highest 8.3% yield and 94% selectivity to phenol in direct hydroxylation of benzene with H2O2.

Graphene vanadic acid (GVA) as a novel heterogeneous catalyst for highly selective benzene hydroxylation under mild conditions

In the present study, Graphene Vanadic Acid (GVA) is introduced as a novel catalyst for high-efficiency hydroxylation of benzene to phenol using hydrogen peroxide at ambient conditions. Graphene oxide as a famous carbon support has converted to a high-performance catalyst through the functionalization using vanadium oxytrichloride (VOCl3). This new carbon compound is regarded as the efficient catalyst due to the prominent advantages such as high-recativity and reusability, facile preparation, active Lewis and Bronsted acid sites, high potential for development of various oxidation reactions, and high thermal, chemical, and physical stability due to the regular carbon structure. GVA progressed the benzene oxidation toward the phenol formation as a useful raw material. Cause of the considerable reactivity of the synthesized catalyst, a minimum amount of hydrogen peroxide was required and the benzene oxidation carried out using an equimolar ratio of benzene/H2O2, and phenol obtained with a remarkable yield (28.2%) as the sole product.

Optimization, reconstruction and heterologous expression of the gene cluster encoding toluene/o-xylene monooxygenase from Pseudomonas stutzeri in Escherichia coli and its successive hydroxylation of toluene and benzene

Biological treatment is a cost-effective and environmentally friendly technique for treating toluene. However, this process is limited by the type and quantity of toluene degraders that can be applied to different environments and methods. It is a feasible solution to constructing new genetic engineering organisms for toluene degradation through biotechnology. To facilitate genetic manipulation and improve gene expression, the toluene/o-xylene monooxygenase locus from Pseudomonas stutzeri was reconstructed and artificially synthesized. All six genes were optimized and driven with a monocistronic transcriptional pattern by T7 promoter and terminator to be expressed at a high level. The engineered bacteria can hydroxylate toluene to a mixture of o-, m- and p-cresol, which are then further oxidized to 3- and 4-methylcatechol. Benzene can also be oxidized to phenol, catechol and pyrogallol successively. The negative effects of toluene can be removed by the engineered bacteria via proteomics analysis. Overall, the artificial gene clusters established in this study can be used to construct different toluene and benzene degradation organisms for bioremediation. Supplemental data for this article is available online at https://doi.org/10.1080/13102818.2021.1996267 .

Hydroxylation of benzene to phenol over heteropoly acid H5PMo10V2O40 supported on amine-functionalized MCM-41.

Supported catalysts with Keggin type heteropoly acids (H5PMo10V2O40) loaded onto amine-functionalized MCM-41 for the catalytic hydroxylation of benzene to phenol with H2O2 were prepared by a wet impregnation method. The effects of the preparation conditions on the properties and activity of the supported catalysts were fully investigated. The results showed that the catalyst retained the mesoporous structure of MCM-41 and H5PMo10V2O40 was dispersed uniformly on the surface of the amine-functionalized MCM-41. Meanwhile, the reusability and catalytic performance of the catalyst were affected by two key factors, i.e., the interaction between the heteropoly acid and the surface of MCM-41, and the hydrophobicity of the catalyst since they decide the leaching of H5PMo10V2O40 and the adsorption of benzene. The catalyst with H5PMo10V2O40 loaded onto amine-functionalized MCM-41, which was prepared using ethanol as the solvent, exhibited the highest phenol yield (20.4%), a turnover frequency value of 20.3 h−1 and good reusability. We believe this work offers an effective and facile strategy for the preparation of a new catalyst for hydroxylation of benzene to phenol.

Photocatalytic hydroxylation of benzene to phenol over organosilane-functionalized FeVO4 nanorods

Surface silylation of FeVO4 with organosilane functional groups is a promising strategy to realize kinetic control of photocatalytic benzene hydroxylation reactions.

Ferrocene-based conjugated microporous polymer and its multiwalled carbon nanotube composite for direct photocatalytic benzene hydroxylation to phenol.

Ferrocene is used as a catalytically active site and building block to construct a new conjugated microporous polymer (CMP), named Fc-POP. A corresponding carbon nanotube composite (CNTs@Fc-POP) with tubular structure was obtained through the π–π interaction between multi-walled carbon nanotubes (MWCNTs) and reactive molecules. This innovative modification method of carbon nanotubes provides a way to construct functionalized carbon materials. The two materials can achieve high conversion and selectivity of benzene hydroxylation to phenol under light irradiation using hydrogen peroxide (H2O2) as an oxidant. Due to the synergistic effect between the carbon nanotubes and the ferrocene group, the incorporation of MWCNTs can improve the yield of phenol significantly. This work explores a new photocatalystic system and expands the related photocatalytic application of CNTs.

A novel heterogeneous catalyst NH2-MIL-88/PMo10V2 for the photocatalytic activity enhancement of benzene hydroxylation

In this work, heterogeneous catalyst NH2-MIL-88/PMo10V2-3 has shown the high hydroxylation activity of benzene under visible light (a 5 W LED), which mainly attributed to the production of hydroxyl radical(˙OH) and V5+/V4+ redox pair in the existence of electron (e−).

Heterogeneous recyclable copper oxide supported on activated red mud as an efficient and stable catalyst for the one pot hydroxylation of benzene to phenol

Phenol is a key intermediate in chemical industry. The present research work reports facile synthesis of a new copper supported activated red mud as a heterogeneous catalyst for oxidative conversion of benzene to phenol. The process is simple and efficient for one pot hydroxylation reaction using H2O2 as an oxidant. The catalyst was characterized using FTIR, XRD, TEM, XPS and BET surface area analyzer. Catalyst reducible properties were studied using H2-TPR technique. The one-pot hydroxylation reaction, carried out at 75 °C under optimum reaction conditions in presence of catalytic material, shows conversion of benzene to phenol with 84.5 % and 87.1 % selectivity and conversion efficiency, respectively. The proposed mechanism emphasizes upon cooperative effect of residual and embedded metal ions in solid catalyst matrix as the contributing factor for efficient conversion and selectivity. The reusable properties of the material, tested up to 5th consecutive cycles of batch operation, indicate retention of selectivity (83.9 %) as well as conversion efficiency (86.7 %), suitable for future commercial development adhering to the principle of green chemistry.

Polyoxometalate-Based Metal-Organic Frameworks with Unique High-Nuclearity Water Clusters.

The maximum exposure of polyoxometalates (POMs) is of great significance to enhance the catalytic performance of HKUST-1 with incorporated Keggin-type POMs. Herein, two phosphovanadomolybdates were encapsulated into the HKUST-1 via a hydrothermal method to obtain two polyoxometalate-based metal-organic frameworks, formulated as [Cu12(BTC)8(H2O)12][H4PMo11VO40]@(H2O)30 (1) and [Cu12(BTC)8(H2O)12][H5PMo10V2O40]@(H2O)49 (2). Single-crystal X-ray diffraction analysis indicates that two compounds contain unique high-nuclearity water clusters without organic counter cations. The octahedral-shaped water cluster (H2O)30 was constructed from square-pyramid-shaped (H2O)5 for compound 1, while the huge cage-shaped water cluster (H2O)49 of compound 2 consisted of crown-like (H2O)8 and one water molecule, which substitute the organic counter cations involved in the structural construction. More importantly, after removing the water clusters via simple heat treatment, the active sites of the two compounds were fully exposed, leading to good catalytic activities for both benzene hydroxylation reaction and oxidative desulfurization. Furthermore, the catalytic test confirmed that compound 2 may be a bifunctional heterogeneous catalyst with great promise for both benzene hydroxylation and oxidative desulfurization.

Transformation kinetics and pathways of sulfamonomethoxine by UV/H2O2 in swine wastewater

Sulfamonomethoxine (SMM), as one of the most predominant antibiotics in animal wastewater, is pending for effective control to minimize its environmental risks. Transformation kinetics and pathways of SMM by UV/H2O2 in swine wastewater were systematically investigated in this study. Direct UV photolysis (as a dominant role) and ∙OH oxidation contributed to SMM degradation in UV/H2O2 system. The less effective reaction rate of SMM in real wastewater than synthetic wastewater (0.1–0.17 vs. ∼0.2–1.5 min−1, despite higher H2O2 dosage and extended reaction time) resulted mainly from the abundant presence of conventional contaminants (indicated by COD, a notable competitor of SMM) in real wastewater. SMM degradation benefited from higher H2O2 dosage and neutral and weak alkaline conditions. However, the effect of initial SMM concentration on SMM degradation in synthetic and real wastewater showed opposite trends, owning to the different probability of SMM molecules to interact with UV and H2O2 in different matrices. Carbonate had an inhibitory effect on SMM degradation by scavenging ∙OH and pH-variation induced effect, while nitrate promoted SMM degradation by generating more ∙OH. The removal efficiency of SMM in real wastewater reached 91% under the reaction conditions of H2O2 of 10 mM, reaction time of 60 min, and pH 6.7–6.9. SMM degradation pathway was proposed as hydroxylation of benzene and pyrimidine rings, and secondary amine, and the subsequent cleavage of S–N bond.

Oxo-vanadium (IV) phthalocyanine implanted onto the modified SBA-15 as a catalyst for direct hydroxylation of benzene to phenol in acetonitrile-water medium: A kinetic study

Direct hydroxylation of benzene using molecular oxygen is an engaged approach to yield of phenol as a valuable compound with numerous applications. In the present research, highly selective benzene hydroxylation was successfully carried out in the presence of O2 using vanadyl phthalocyanine implanted onto the chloro-functionalized SBA-15 as a robust catalyst. Also, the effect of water as a co-solvent was investigated and it was concluded that the mixed solvent (CH3CN-H2O) can play a remarkable role in the development of the reaction progress due to its ability to act as an axial ligand. Then, the oxidation of benzene using CH3CN and CH3CN-H2O was kinetically investigated.

Light‐Induced Efficient Hydroxylation of Benzene to Phenol by Quinolinium and Polyoxovanadate‐Based Supramolecular Catalysts

AbstractDirect Hydroxylation of benzene to phenol with high yield and selectivity has been the goal of phenol industrial production. Photocatalysis can serve as a competitive method to realize the hydroxylation of benzene to phenol owing to its cost‐effective and environmental friendliness, however it is still a forbidding challenge to obtain good yield, high selectivity and high atom availability meanwhile. Here we show a series of supramolecular catalysts based on alkoxohexavanadate anions and quinolinium ions for the photocatalytic hydroxylation of benzene to phenol under UV irradiation. We demonstrate that polyoxoalkoxovanadates can serve as efficient catalysts which can not only stabilize quinolinium radicals but also reuse H2O2 produced by quinolinium ions under light irradiation to obtain excellent synergistic effect, including competitive good yield (50.1 %), high selectivity (>99 %) and high atom availability.