Phenol Oxidation Reaction Research Articles

Effect of ultra-high pressure heat-assisted technology combined with L-cysteine on the color of ready-to-eat shrimp during storage

This study used ultra-high pressure processing (HPP) heat-assisted technology combined with L-cysteine (L-cys) to process ready-to-eat (RTE) shrimp. Subsequently, the effects of physical field and chemical modifications on the color of RTE shrimp were studied. The results showed that the RTE shrimp treated with HPP-Heat-L-cys showed better performance in terms of brightness value (65.25) and astaxanthin (AST) content (0.71 μg/g) during storage, maintaining the original color of RTE shrimp effectively. In addition, it was observed that the application of HPP-Heat-L-cys significantly delayed phenol oxidation, lipid oxidation, and Maillard reaction compared with traditional HPP or heat treatments. Specifically, the total phenolic content of RTE shrimp treated with HPP-Heat-L-cys was higher than that of other samples, but the TBARS and browning index were lower. Furthermore, HPP-Heat-L-cys could delay the production of dark products (such as 2-methylanthraquinone, p-benzoquinone, lipofuscin and melanin), ultimately safeguarding the color stability of RTE shrimp during storage.

Energy‐Efficient Co‐production of Benzoquinone and H2 Using Waste Phenol in a Hybrid Alkali/Acid Flow Cell

AbstractIn both the manufacturing and chemical industries, benzoquinone is a crucial chemical product. A perfect and economical method for making benzoquinone is the electrochemical oxidation of phenol, thanks to the traditional thermal catalytic oxidation of phenol process requires high cost, serious pollution and harsh reaction conditions. Here, a unique heterostructure electrocatalyst on nickel foam (NF) consisting of nickel sulfide and nickel oxide (Ni9S8‐Ni15O16/NF) was produced, and this catalyst exhibited a low overpotential (1.35 V vs. RHE) and prominent selectivity (99 %) for electrochemical phenol oxidation reaction (EOP). Ni9S8‐Ni15O16/NF is beneficial for lowering the reaction energy barrier and boosting reactivity in the EOP process according to density functional theory (DFT) calculations. Additionally, an alkali/acid hybrid flow cell was successfully established by connecting Ni9S8‐Ni15O16/NF and commercial RuIr/Ti in series to catalyze phenol oxidation in an alkaline medium and hydrogen evolution in an acid medium, respectively. A cell voltage of only 0.60 V was applied to produce a current density of 10 mA cm−2. Meanwhile, the system continued to operate at 0.90 V for 12 days, showing remarkable long‐term stability. The unique configuration of the acid‐base hybrid flow cell electrolyzer provides valuable guidance for the efficient and environmentally friendly electrooxidation of phenol to benzoquinone.

Energy-Efficient Co-production of Benzoquinone and H2 Using Waste Phenol in a Hybrid Alkali/Acid Flow Cell.

In both the manufacturing and chemical industries, benzoquinone is a crucial chemical product. A perfect and economical method for making benzoquinone is the electrochemical oxidation of phenol, thanks to the traditional thermal catalytic oxidation of phenol process requires high cost, serious pollution and harsh reaction conditions. Here, a unique heterostructure electrocatalyst on nickel foam (NF) consisting of nickel sulfide and nickel oxide (Ni9S8-Ni15O16/NF) was produced, and this catalyst exhibited a low overpotential (1.35 V vs. RHE) and prominent selectivity (99 %) for electrochemical phenol oxidation reaction (EOP). Ni9S8-Ni15O16/NF is beneficial for lowering the reaction energy barrier and boosting reactivity in the EOP process according to density functional theory (DFT) calculations. Additionally, an alkali/acid hybrid flow cell was successfully established by connecting Ni9S8-Ni15O16/NF and commercial RuIr/Ti in series to catalyze phenol oxidation in an alkaline medium and hydrogen evolution in an acid medium, respectively. A cell voltage of only 0.60 V was applied to produce a current density of 10 mA cm-2. Meanwhile, the system continued to operate at 0.90 V for 12 days, showing remarkable long-term stability. The unique configuration of the acid-base hybrid flow cell electrolyzer provides valuable guidance for the efficient and environmentally friendly electrooxidation of phenol to benzoquinone.

Ferrocene-functionalized zirconium-oxo clusters for achieving high-performance thermocatalytic redox reactions

The Zr(IV) ions are easily hydrolyzed to form oxides, which severely limits the discovery of new structures and applications of Zr-based compounds. In this work, three ferrocene (Fc)-functionalized Zr-oxo clusters (ZrOCs), Zr9Fc6, Zr10Fc6 and Zr12Fc8 were synthesized through inhibiting the hydrolysis of Zr(IV) ions, which show increased nuclearity and regular structural variation. More importantly, these Fc-functionalized ZrOCs were used as heterogeneous catalysts for the transfer hydrogenation of levulinic acid (LA) and phenol oxidation reactions for the first time, and displayed outstanding catalytic activity. In particular, Zr12Fc8 with the largest number of Zr active sites and Fc groups can achieve > 95% yield for LA-to-γ-valerolactone within 4 h (130 °C) and > 98% yield for 2,3,6-trimethylphenol-to-2,3,5-trimethyl-p-benzoquinone within 30 min (80 °C), showing the best catalytic performance. Catalytic characterization combined with theory calculations reveal that in the Fc-functionalized ZrOCs, the Zr active sites could serve as substrate adsorption sites, while the Fc groups could act as hydrogen transfer reagent or Fenton reagent, and thus achieve effectively intramolecular metal–ligand synergistic catalysis. This work develops functionalized ZrOCs as catalysts for thermal-triggered redox reactions.

Catalysts Based on Iron Oxides for Wastewater Purification from Phenolic Compounds: Synthesis, Physicochemical Analysis, Determination of Catalytic Activity

In this work, the synthesis of magnetite nanoparticles and catalysts based on it stabilized with silicon and aluminum oxides was carried out. It is revealed that the stabilization of the magnetite surface by using aluminum and silicon oxides leads to a decrease in the size of magnetite nanocrystals in nanocomposites (particle diameter less than ~10 nm). The catalytic activity of the obtained catalysts was evaluated during the oxidation reaction of phenol, pyrocatechin and cresol with oxygen. It is well known that phenolic compounds are among the most dangerous water pollutants. The effect of phenol concentration and the effect of temperature (303–333 K) on the rate of oxidation of phenol to Fe3O4/SiO2 has been studied. It has been determined that the dependence of the oxidation rate of phenol on the initial concentration of phenol in solution is described by a first-order equation. At temperatures of 303–313 K, incomplete absorption of the calculated amount of oxygen is observed, and the analysis data indicate the non-selective oxidation of phenol. Intermediate products, such as catechin, hydroquinone, formic acid, oxidation products, were found. The results of UV and IR spectroscopy showed that catalysts based on magnetite Fe3O4 are effective in the oxidation of phenol with oxygen. In the UV spectrum of the product in the wavelength range 190–1100 nm, there is an absorption band at a wavelength of 240–245 nm and a weak band at 430 nm, which is characteristic of benzoquinone. In the IR spectrum of the product, absorption bands were detected in the region of 1644 cm−1, which is characteristic of the oscillations of the C=O bonds of the carbonyl group of benzoquinone. The peaks also found at 1353 cm−1 and 1229 cm−1 may be due to vibrations of the C-H and C-C bonds of the quinone ring. It was found that among the synthesized catalysts, the Fe3O4/SiO2 catalyst demonstrated the greatest activity in the reaction of liquid-phase oxidation of phenol.

A New Thiolate-Bound Dimanganese Cluster as a Structural and Functional Model for Class Ib Ribonucleotide Reductases.

In class Ib ribonucleotide reductases (RNRs) a dimanganese(II) cluster activates superoxide (O2 ⋅- ) rather than dioxygen (O2 ), to access a high valent MnIII -O2 -MnIV species, responsible for the oxidation of tyrosine to tyrosyl radical. In a biomimetic approach, we report the synthesis of a thiolate-bound dimanganese complex [MnII 2 (BPMT)(OAc)2 ](ClO)4 (BPMT=(2,6-bis{[bis(2-pyridylmethyl)amino]methyl}-4-methylthiophenolate) (1) and its reaction with O2 ⋅- to form a [(BPMT)MnO2 Mn]2+ complex 2. Resonance Raman investigation revealed the presence of an O-O bond in 2, while EPR analysis displayed a 16-line St =1/2 signal at g=2 typically associated with a MnIII MnIV core, as detected in class Ib RNRs. Unlike all other previously reported Mn-O2 -Mn complexes, generated by O2 ⋅- activation at Mn2 centers, 2 proved to be a capable electrophilic oxidant in aldehyde deformylation and phenol oxidation reactions, rendering it one of the best structural and functional models for class Ib RNRs.

Photocatalytic phenol oxidation over ball milled hexagonal boron nitride

Due to their high toxicity, even a small amount of phenols entering the surrounding aquatic environment poses a serious danger to all living beings. To address this important problem, commercial micron-sized h-BN powder was ball milled at 450, 600 and 750 rpm, surface-functionalized with hydroxyl and amino groups by sonication, and characterized as a promising photocatalyst. The samples were studied by X-Ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, 11B nuclear magnetic resonance, scanning and transmission electron microscopy, diffuse reflectance ultraviolet–visible spectroscopy and photoluminescence spectroscopy. At all rates of mechanical processing without the use of auxiliary reagents, exfoliation of h-BN flakes was achieved. An increase in the ball milling rate led to a decrease in crystallinity and structure refinement, which was accompanied by the formation of a large number of dislocations and nanocrystallites 2–5 nm in size. Upon subsequent sonication, the BN powder underwent partial oxidation and functionalization with O(H) groups. The observed increase in the photocatalytic activity of ball-milled h-BN particles in the phenol oxidation reaction is explained by an increase in the 254 nm UV-light absorption, a decrease in the rate of electron-hole recombination, and an increase in the formation rate of OH radicals. Our results clearly show the promise of ball milled commercial micron-sized h-BN powder as a photocatalyst in the phenol oxidation reaction.

Zeolite Incorporated Copper-Schiff Base Complex: Synthesis, Characterization and Heterogeneous Catalytic Oxidation

A zeolite immobilized hybrid catalyst Cu(MeO-salpn)-NaY has been synthesized by incorporating Cu(II) Schiff base [where MeO-salpnH2 is N,N′-(propane-1,3)-bis-(3-methoxysalicylaldiimine)] complex in the porous matrix of zeolite NaY. The prepared hybrid material has been characterized by infrared, UV-visible spectra, powder X-ray diffraction (XRD) and thermogravimetric (TG-DTA) analyses. The X-ray powder diffraction analysis showed that the crystalline integrity of the pristine NaY zeolite remained intact upon immobilization of the complex. Spectroscopic study indicates that CuN2O2 basal plane of neat complex undergoes distortion upon immobilization of the complex in zeolite cavity. The hybrid catalyst was employed in the oxidation reactions of phenol and 1-naphthol and found to be catalytically active with impressive selectivity. At the same time, free complex [Cu(MeO-salpn)(H2O)] and hybrid material Cu-NaY were prepared and applied for the same reactions, but the catalytic activity of these species were found to be very poor. This study shows that there occurs a distortion of the coordination environment around copper(II) upon immobilization which is a major reason behind the different catalytic activity of these copper-Schiff base systems.

Application of MIL-53(Fe) metal-organic framework material in catalytic wet oxidation of phenol

In the present study, MIL-53(Fe) metal-organic framework material was applied as catalyst for phenol oxidation reaction in aqueous solution with H2O2 under UV radiation. The materials were characterized using X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FT-IR). The effects of reaction time, initial phenol concentration, and initial pH of the solution on phenol oxidation reactions were investigated. The results indicated that MIL-53(Fe) could work effectively in the wide pH range from 2 to 10. Phenol was quickly oxidized to form simple organic acids, including acetic acid, formic acid and oxalic acid.

Easily fabricated Fe/Se soft magnetic material for catalytic phenol oxidation

The novel Fe/Se soft magnetic material could be obtained easily by heating equal molar of selenium and iron powders. The saturation magnetization, residual magnetic field strength and coercive force of the material were 50.9 emu/g, 1.78 emu/g and 175.7 Oe, respectively, in accordance with the characteristic parameters of the soft magnetic materials. The material could catalyze the phenol oxidation reaction to produce p-benzoquinone selectively. As a selenium-containing magnetic substance, the material can give full play to the properties of selenium and magnetic materials at the same time, and thus may be of profound application values in industry.

СИНТЕЗ ТА ФОТОКАТАЛІТИЧНА АКТИВНІСТЬ ПОКРИТТІВ TI/TInOm∙ZRO2 ДЛЯ ОЧИЩЕННЯ ПРОМИСЛОВИХ СТІЧНИХ ВОД ВІД ОРГАНІЧНИХ АРОМАТИЧНИХ ЗАБРУДНИКІВ

It is shown that photocatalytic processes on semiconductor materials are promising for use in technologies for purifying industrial waste water and air from toxic organic impurities for solving important environmental problems. Studies on the formation of coatings with titanium(IV) oxide supplemented with zirconium(IV) oxide have been carried out. The Ti/TiO2 coverings were formed by anodic oxidation of technical alloys of VT1-0 grade titanium and E-125 zirconium from aqueous electrolyte solutions based on 0.5 M sulfuric acid and 1 M potassium pyrophosphate. To obtain mixed oxide coatings of the Ti/TinOm·ZrO2 composition, zirconium(IV) oxide of a given concentration was additionally introduced into the electrolyte solutions. The photocatalytic activity of the obtained systems was assessed by the phenol oxidation reaction. It is shown that, as a result of anodic oxidation of the VT1-0 alloy in sulfuric and pyrophosphate electrolytes, it is possible to obtain mixed oxide systems of the Ti/TinOm·ZrO2 composition with a porous and microcrystalline surface structure and a zirconium content of up to 2 % by weight. It was found that an increase in the pH of the electrolyte leads to a significant decrease in the content of zirconium in the coatings. It is shown that the contact masses Ti/TiO2, Zr/ZrO2, Ti/TinOm·ZrO2 are photocatalytically active in the oxidation of phenol under the action of UV radiation, and the mixed Ti/TinOm·ZrO2 coatings formed from a sulfuric acid electrolyte exhibit a higher catalytic activity with respect to compared with both individual oxides and Ti/TinOm·ZrO2 deposited from pyrophosphate electrolytes. The results obtained indicate the possibility of creating photocatalytic converters using mixed oxide systems formed on metal supports for purifying wastewater from organic aromatic compounds. Keywords: coatings, titanium(IV) oxide, electrochemical anodizing, photocatalytic activity, zirconium(IV) oxide, organic aromatic pollutants, phenol, waste water, purification. Corresponding author Panasenrj V.A. е-mail: office@niochim.kharkov.ua

Oxidative destruction of phenol on Fe/SiO2 catalysts.

In the present study, the sol-gel technique helped to obtain Fe-containing samples with a base of amorphous silicon dioxide from rice husks RH-Fe and RH-Fe-300. These materials are characterized by IR spectroscopy, X-ray phase and X-ray spectral analysis. It was shown that the samples contain silicate structures Si-O-Si(Fe) and are in an amorphous state. Structure of the surface layers of RH-Fe-300 catalyst particles was established for the first time using X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectra (EDX) methods. It was shown that the surface layers of the synthesized particles are oxygen depleted due to oxygen vacancies and silanol groups, therefore defects can form in its structure. Photocatalytic activity of the samples in the phenol oxidation reaction under ultraviolet and solar irradiation in the presence of hydrogen peroxide was studied. It was shown that the degree of phenol decomposition in the presence of RH-Fe for 24 hours under solar irradiation was 92%, in the presence of RH-Fe - 17%. Under two-stage irradiation (ultraviolet and solar), the percentage of phenol decomposition using both catalysts after a day amounted to more than 80%. It was established that RH-Fe-300 catalyst increases oxidation of phenolic compounds in alkaline rice husk hydrolysates under solar irradiation in the presence of hydrogen peroxide.

Synthesis of Cu2O/TiO2 Composite Photocatalysts for Wastewater Treatment

The properties of composite photocatalysts based on a coating of TiO2 nanotubes (NT TiO2) and Cu2O particles are presented. Coatings of nanotubes were obtained by the anodization method, after which particles of copper (I) oxide were deposited by the method of ion layering on the NT surface. The morphology and composition of the resulting composite catalysts were studied. The synthesized catalysts were shown to exhibit high photocatalytic activity in the phenol oxidation reaction in an aqueous medium under normal conditions. The maximum degree of phenol oxidation in 1 h on the developed photocatalysts was 82 %. The dependence of the catalytic activity on the number of layers of deposition of copper oxide on the coatings of nanotubes of titanium dioxide (NT TiO2) is established.

Ti-Doped SBA-15 Catalysts Used in Phenol Oxidation Reactions.

Two Ti-SBA-15 catalysts are synthesized using techniques that should either deposit Ti atoms specifically at the SBA-15 surface or allow Ti-containing species to exist at both the surface and within the bulk of SBA-15. The materials have been characterized by Fourier transform infrared (FTIR), Raman and UV visible spectroscopies, transmission electron microscopy, scanning electron microscopy/energy-dispersive X-ray spectrometry microscopies, and N2 physisorption experiments. They have been applied in the total oxidation of phenol under catalytic wet air oxidation (CWAO) conditions and using photo- and plasma promotion. The materials retain the structure of SBA-15 following the doping in both cases and Ti incorporation is confirmed. The nature of the incorporated Ti remains unclear—with evidence for anatase TiO2 (from Raman and UV vis analysis) and evidence for atomically dispersed Ti from FTIR. In terms of reactivity, the presence of Ti in the in situ-prepared catalyst improves reactivity in the photopromoted reaction (increasing conversion from 28 to 60%), while both Ti catalysts improve reactivity in the CWAO reaction (by 7% over the in situ catalyst and by 25% over the grafted material). The presence of Ti has no beneficial effect on conversion in the plasma-promoted reaction. Here, however, Ti does affect the nature of the oxidized intermediates formed during the total phenol oxidation.

MIL-100(Fe) metal–organic framework catalyzed oxidation of phenol revisited: dark-Fenton activity of the catalyst

This work presents the Fenton-type aqueous-phase oxidation of phenol with two MIL-100(Fe) catalysts prepared by hydrothermal and reflux methods. The catalysts were systematically characterized by infrared spectroscopy, X-ray powder diffraction, thermogravimetry, scanning electron microscopy, and surface analysis techniques. The influence of various experimental parameters on the course of the oxidation process conducted at room temperature was examined. The catalysts showed significant stability when phenol/H2O2 = 1:1 molar ratio was applied. In this case, 93% conversion was obtained with minimal iron leaching (ca. 0.2%). The hydrothermally prepared MIL-100(Fe) catalyst displayed higher catalytic activity due to its larger surface area. The results were also discussed to evaluate the “dark-Fenton” contribution of the system in “photo-Fenton” reactions previously reported with similar catalysts for phenol oxidation. This study has demonstrated that dark-Fenton reaction with MIL-100(Fe) catalysts has an important contribution to the mineralization of phenol without requiring irradiation or ZnO assistance. A schematic illustration of the fabrication processes of MIL-100(Fe) catalysts and their use in Fenton-type phenol oxidation reaction.

Surface-Plasmon-Resonance-Induced Photocatalysis by Core-Shell SiO2@Ag NCs@Ag3PO4 toward Water-Splitting and Phenol Oxidation Reactions.

A series of core-shell-structured SiO2@Ag NCs@Ag3PO4 photocatalysts with varying percentages of silver nanoclusters (Ag NCs) have been synthesized by using SiO2 as a core material. The crystal structure, morphology, chemical composition, and photophysical properties of as-synthesized materials have been thoroughly analyzed through powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse-reflectance spectroscopy, and photoluminescence (PL) spectroscopy techniques. The introduction of Ag NCs has effectively reduced the photogenerated electron-hole recombination rate, as evidenced from PL and Nyquist plots. The electrochemical properties of the photocatalysts were studied through photocurrent measurement, and 23-fold current enhancements in the cathodic direction are observed. The excellent current enhancement by the photocatalyst is attributed to the presence of Ag NCs. The effectiveness of the photocatalysts toward photocatalytic water splitting was studied and produced 2460 μmol h-1 g-1 hydrogen and 1236 μmol h-1 g-1 oxygen by 2 wt % loaded Ag NCs. Again the photocatalytic phenol oxidation has been explored, and the best catalyst is able to oxidize 91% phenol upon visible-light irradiation. The photocatalyst having 2 wt % Ag NCs shows better activity toward both water splitting and phenol oxidation compared to others, which is attributed to better visible-light absorption efficiency, lower electron-hole recombination rate, and low interfacial charge-transfer resistance.

New phosphazene nanospheres anchored Fe(III), Co(II) and Cu(II) Schiff base complexes as efficient catalysts in oxidation of phenol

New phosphazene nanosphere-supported Fe(III), Co(II) and Cu(II) Schiff base complexes were prepared and their catalytic activities were investigated. The synthesized compounds were characterized by various techniques such as FT-IR, XRD, TGA, SEM, EDX, and atomic absorption spectroscopy. The average diameters of these nanosphere compounds are about 250 nm and they are spherically uniform with very good stability. The effect of the support on catalytic activity of the metal complexes was determined by investigating the oxidation of phenol under different experimental conditions. These complexes exhibit high activity in oxidation of phenol under relatively mild condition in the presence of urea hydrogen peroxide (UHP) as an oxidant. The influence of various parameters such as amount of catalyst, phenol:UHP molar ratio, and temperature on the rate of the oxidation reaction of phenol was also evaluated. Based on the characterization results and the experimental evidences a plausible mechanism has been proposed.

Electrochemical CO2 Reduction Using Electrons Generated from Photoelectrocatalytic Phenol Oxidation

AbstractElectrochemical CO2 reduction (ECCO2R) requires electrons, for example, from oxygen evolution reaction (OER). However, such a multiple‐electron‐involved reaction is complicated and kinetically slow, leading to high overpotential. Herein, OER is replaced with photoelectrocatalytic phenol oxidation reaction (PECPOR) that provides electrons for ECCO2R. In an integrated cell, ECCO2R is conducted on the cathode of Cu nanowires and PECPOR is performed on the anode of SnO2 and Sb coated TiO2 nanotubes. Significant improvement of ECCO2R into CO and hydrocarbons is realized when PECPOR is conducted at a high current density. The use of this integrated system results in the reduction of the specific energy consumption by a factor of 51.33%, compared with the utilization of two half‐cells for individual ECCO2R and PECPOR. This study thus proposes a novel strategy to couple ECCO2R with PECPOR and eventually to tackle the problems of environmental pollution and energy crisis.

Substituent effects on the oxidation reactions of 4-nitrophenol, phenol, 4-methylpheol, and 4-methoxyphenol mediated by reduced graphene oxide in water

Substituent effects of 4-nitrophenol (4-NP), phenol (PE), 4-methylpheol (4-MP), and 4-methoxyphenol (4-MOP) on their oxidative coupling reactions mediated by reduced graphene oxide (rGO) were examined using a batch method. The reaction products were identified as the oligomers of their individual parent compound, and CC and CO coupling between phenolic radicals were the main reaction pathways. The oxidative kinetics were well described with pseudo-first order model. The rate constants (kobs) of 4-NP, PE, 4-MP and 4-MOP were 0.47 × 10−3, 1.00 × 10−3, 2.03 × 10−3, and 3.53 × 10−3 h−1, respectively, following the order 4-NP < PE < 4-MP < 4-MOP. The kobs of four phenolic compounds was negative linear correlation with their homolytic bond dissociation energies (BDE(OH)), suggesting that BDE(OH) was an effective indicator to predict the oxidation susceptibility of phenolic compounds in rGO system. Dissolved oxygen played a critical role in the oxidation reactions through the formation of superoxide anion (O2−) on rGO. These O2− further cleaved the OH bond of phenolic compounds to produce phenolic radicals, which interacted each other and led to the following oxidative coupling reactions. The finding of this study is important for predicting the environmental fate of rGO and phenolic compounds.

Impact of zeolite-Y framework on the geometry and reactivity of Ru (III) benzimidazole complexes – A DFT study

A detailed comparative Density Functional Theory (DFT) study is made to understand the structural changes of the guest complex due to steric and electronic interactions with the host framework. In this study, Ru(III) benzimidazole and 2- ethyl Ru(III) benzimidazole complexes encapsulated in a supercage of zeolite Y. The zeolitic framework integrity is not disturbed by the intrusion of the large guest complex. A blue shift in the d–d transition observed in the UV-Visible spectroscopic studies of the zeolite encapsulated complexes and they shows a higher catalytic efficiency. Encapsulation of zeolite matrix makes the metal center more viable to nucleophilic attack and favors the phenol oxidation reaction. Based on the theoretical calculations, transition states and structures of reaction intermediates involved in the catalytic cycles are derived.