High Phenol Conversion Research Articles

Efficient Electrosynthesis of Valuable para-Benzoquinone from Aqueous Phenol on NiRu Hybrid Catalysts.

Electrocatalytic oxidation of aqueous phenol to para-benzoquinone (p-BQ) offers a sustainable approach for both pollutant abatement and value-added chemicals production. However, achieving high phenol conversion and p-BQ yield under neutral conditions remains challenging. Herein, we report a Ni(OH)2-supported Ru nanoparticles (NiRu) hybrid electrocatalyst, which exhibits a superior phenol conversion of 96.5% and an excellent p-BQ yield of 83.4% at pH 7.0, significantly outperforming previously reported electrocatalysts. This exceptional performance benefits from the triple synergistic modulation of the NiRu catalyst, including enhanced phenol adsorption, increased p-BQ desorption, and suppressed oxygen evolution. By coupling a flow electrolyzer with an extraction-distillation separation unit, the simultaneous phenol removal and p-BQ recovery are realized. Additionally, the developed electrocatalytic system with the NiRu/C anode displays good stability, favorable energy consumption, and reduced greenhouse gas emissions for phenol-containing wastewater treatment, demonstrating its potential for practical applications. This work offers a promising strategy for achieving low-carbon emissions in phenol wastewater treatment.

Efficient Electrosynthesis of Valuable para‐Benzoquinone from Aqueous Phenol on NiRu Hybrid Catalysts

AbstractElectrocatalytic oxidation of aqueous phenol to para‐benzoquinone (p‐BQ) offers a sustainable approach for both pollutant abatement and value‐added chemicals production. However, achieving high phenol conversion and p‐BQ yield under neutral conditions remains challenging. Herein, we report a Ni(OH)2‐supported Ru nanoparticles (NiRu) hybrid electrocatalyst, which exhibits a superior phenol conversion of 96.5 % and an excellent p‐BQ yield of 83.4 % at pH 7.0, significantly outperforming previously reported electrocatalysts. This exceptional performance benefits from the triple synergistic modulation of the NiRu catalyst, including enhanced phenol adsorption, increased p‐BQ desorption, and suppressed oxygen evolution. By coupling a flow electrolyzer with an extraction‐distillation separation unit, the simultaneous phenol removal and p‐BQ recovery are realized. Additionally, the developed electrocatalytic system with the NiRu/C anode displays good stability, favorable energy consumption, and reduced greenhouse gas emissions for phenol‐containing wastewater treatment, demonstrating its potential for practical applications. This work offers a promising strategy for achieving low‐carbon emissions in phenol wastewater treatment.

Continuous liquid-phase alkylation of lignocellulose-derived phenolics and cyclopentanol under large space velocity for efficient synthesis of high-performance biofuel

It is significant to efficiently and feasibly produce high-performance jet fuel from renewable biomass. We reported here that lignin-derived phenolics can be alkylated by cellulose-derived cyclopentanol in a continuous-flow fixed-bed reactor packed with HUSY zeolite without the use of solvents. Under nitrogen pressure, the liquid-phase reaction was achieved. Among the investigated zeolites with different structures and SiO2/Al2O3, HUSY-150 exhibited excellent catalytic performance and stability. By adjusting reaction conditions, almost complete conversion of cyclopentanol was achieved, as well as high phenol conversion (∼70 %), and high polycyclic product selectivity (>95 %) over HUSY-150. Afterwards, we extended the range of feedstock from phenol to other phenolics (guaiacol, 2,6-dimethoxyphenol, and lignin oil surrogates), and even at a high LHSV (liquid hourly space velocity) of 36 mL/(gcat·h), HUSY-150 maintained robust catalytic activity. This study demonstrates a feasible and effective method for producing high-performance jet fuel blends using lignocellulose-derived compounds.

Fabricating Pt0-acid synergy in Pt/Beta phenol hydrodeoxygenation catalysts via a surface modification strategy of Beta molecular sieves

As for metal/zeolite supported phenol hydrodeoxygenation catalysts, it is important to improve the dispersion of metallic sites and build synergistic relationship between metallic and acid sites. The current research proposes a surface modification strategy by introducing CTAB in the NaOH etching of Beta. CTAB interacts with crystal defects to inhibit excessive crystal destruction. Aluminum atoms are protected from being removed and acid sites are reserved. Generated silicon hydroxyl groups anchor Pt0 particles. Pt0 particles are spatial resisted on the internal surface of catalysts to activate C–O bonds of phenol. Preserved acid sites provide reactive sites for dehydration reaction of cyclohexanol on the external surface of Pt/Beta-H. The high phenol conversion (i.e., 92.26 %) and cyclohexane yield (i.e., 7.18 %) were obtained at 80 °C due to the functional synergistic effect between acid and Pt0 sites. Proposed surface modification strategy proposes references for the structure design and development of efficient phenolics hydrodeoxygenation catalysts.

Active Carbon from Date Stones for Phenol Oxidation in Trickle Bed Reactor, Experimental and Kinetic Study

The catalytic wet air oxidation (CWAO) of phenol has been studied in a trickle bed reactor
 using active carbon prepared from date stones as catalyst by ferric and zinc chloride activation (FAC and ZAC). The activated carbons were characterized by measuring their surface area and adsorption capacity besides conventional properties, and then checked for CWAO using a trickle bed reactor operating at different conditions (i.e. pH, gas flow rate, LHSV, temperature and oxygen partial pressure). The results showed that the active carbon (FAC and ZAC), without any active metal supported, gives the highest phenol conversion. The reaction network proposed accounts for all detected intermediate products of phenol oxidation that composed by several consecutive and parallel reactions. The parameters of the model estimated using experimental data obtained from a continuous trickle bed reactor at different temperatures (120-160 C) and oxygen partial pressures (8-12 bar). Simple power law as well as Langmuir-Hinshelwood (L-H) expressions accounting for the adsorption effects were checked in the modeling of the reaction network. A non-linear multi-parameter estimation approach was used to simultaneously evaluate the high number of model parameters. Approach by simple power law only succeeds in fitting phenol disappearance. Instead, when L-H expressions are incorporated for the intermediate reaction steps, the model accurately describes all the experimental concentration profiles, giving mean deviations below 10%.

Bifunctional Pt/Hβ catalyzed alkylation and hydrodeoxygenation of phenol and cyclohexanol in one-pot to synthesize high-density fuels

Synthesis of fuels from lignin bio-oil feedstock significantly alleviates energy crises and environmental pollution. Phenol is the simplest model compound for lignin bio-oil feedstocks, and the synthesis of fuel precursors from phenol through alkylation has received increasing attention. Here we report a one-pot strategy for preparing polycyclic alkane high-density fuels from phenol and cyclohexanol over bifunctional Pt/Hβ catalyst by combining alkylation with following hydrodeoxygenation (HDO). The activity of different zeolites for catalyzing the alkylation of phenol and cyclohexanol was explored. It was found that the larger pore size of alkali treated Hβ would not limit the production of polycyclic compounds, and good acid content in a particular mesoporous specific surface area can speed up the reaction rate. The one-pot reaction conditions were then optimized. When the alkali treatment concentration is 0.2 mol/L, the metal loading is 0.2 wt%, and the molar ratio of phenol and cyclohexanol is 1:1, the highest conversion of phenol can reach more than 83 %. The selectivity of alkylphenol can reach more than 97 %, and the yield of bicyclic and tricyclic rings in the final product after HDO can reach 83.42 %. The bifunctional catalyst can also realize the coupling of other acid-catalyzed carbon growth reactions and metal-catalyzed HDO reactions, which allows the direct synthesis of fuel from lignin oil or other biomass compounds.

Hybrid Nano‐Structured Pd Catalyst for Selective Hydrogenation of Phenol and the Insights of Deactivation Mechanism

AbstractA catalyst composed of La2O3/AC and Pd nanoparticles is constructed for precise synthesis of cyclohexanone from phenol hydrogenation with high conversion (>99 %) and selectivity (>95 %). The special structure and the synergistic effect remarkably facilitate the high conversion of phenol. The stability test results of the used Pd/@‐La2O3/AC catalyst showed that the phenol conversion decreased from 100 % to 24.5 %. The deactivation reason for the used catalyst was the agglomeration of Pd nanoparticles and the adsorption of organics. Three treatment methods, heat treatment, ethanol wash, and water wash, were regenerated the catalytic activity of the used Pd/@‐La2O3/AC catalyst. The regenerated method of water wash solved the problem of organic matter blockage and residue to a certain extent, but still can not fully recover its high activity. This deactivation mechanism provides important guidance to develop high stable Pd‐based catalyst for the selective hydrogenation of phenol.

Highly active Mg–Al hydrotalcite for efficient O‐methylation of phenol with DMC based on soft colloidal templates

AbstractBACKGROUNDAnisole (AN) is an important compound that has been studied in research into antioxidants, plastic stabilizers, pesticides and dyes. One of the technological alternatives to synthesizing them is using a modified solid catalyst with a soft colloidal template. Synthesis of AN has been demonstrated using dimethyl carbonate (DMC) and phenol over a mixed oxide catalyst derived from Mg–Al hydrotalcite, employing cetyl trimethylammonium bromide (CTAB) as a soft colloidal template.RESULTSWhen the reaction was performed at atmospheric pressure in the presence of catalyst (in an amount of 4.5 wt% with respect to the reactants, DMC and phenol) at 200 °C, and a DMC:phenol molar ratio of 2:1 for 8 h, good results were seen for both phenol conversion and selectivity of AN (87.66% and 99.38%, respectively). The yield of AN was 87.11%.CONCLUSIONThe characterization of the catalyst demonstrated that the calcination temperature has a significant effect on the structure of the obtained Mg–Al hydrotalcite. Its surface properties and pore diameter distribution resulted in an increased concentration of hierarchical basic sites within the material. Weak and moderate basic sites contributed to the high conversion of phenol and good selectivity of AN. In addition, the thermal stability analysis of the as‐prepared Mg–Al mixed oxide showed that the hierarchical structures can be preserved up to 500 °C and eventually be transformed into highly dispersed MgO particles. © 2021 Society of Chemical Industry (SCI).

O-Methylation of Phenol for High Selective Synthesis of Anisole over Calcium Oxide Catalyst

In this article, a CaO-based catalyst was prepared by impregnating potassium salt on CaO to develop a highly efficient heterogeneous catalyst for highly selective synthesis of anisole (AN) from phenol and dimethyl carbonate by a O-methylation. KF/CaO catalysts are highly active and selective towards formation of anisole via methylation of phenol with the highest yield of 97.48% AN was obtained at 200°C. Various reaction parameters including KF loading, the amount of catalyst and the calcination temperature on the catalytic activity were investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), BET, CO2‑TPD and thermogravimetric (TG) were used to characterize the prepared catalyst. It was found that the high catalytic activity of CaO after modification with KF is associated with the structural aspects and the amount of basicity of the catalyst. Temperature programmed desorption of CO2 and XRD studies revealed the K2O species, a strong basic site formed by the substitution of the Ca2+ in CaO lattice by K+, might have great contribution for the high conversion of phenol and good selectivity of anisole.

First Phenol Carboxylation with CO2 on Carbon Nanostructured C@Fe-Al2O3 Hybrids in Aqueous Media under Mild Conditions.

Novel hybrid materials with integrated catalytic properties and hydrophobic response, C@Fe–Al2O3 hybrid samples, were presented and tested as catalysts for phenol reaction in aqueous solutions at atmospheric pressure and mild temperature conditions, using CO2 as a feedstock. A series of carbon-coated γ-alumina pellets (C@Fe–Al2O3) were synthesized and characterized by TGA, Brunauer–Emmett–Teller (BET) method, Raman spectroscopy, SEM, TEM, and XPS in order to get comprehensive knowledge of their properties at the nanoscale and relate them with their catalytic behavior. The results obtained correlated their catalytic activities with their carbon surface compositions. The application of these materials as active catalysts in the Kolbe–Schmitt reaction for CO2 conversion in aqueous media was proposed as an alternative reaction for the valorization of exhausts industrial effluents. In these early tests, the highest conversion of phenol was observed for the hybrid samples with the highest graphitic characteristic and the most hydrophobic behavior. Carboxylation products such as benzoic acid, p-hydroxybenzoic acid, and salicylic acid, have been identified under these experimental conditions.

Photodeposition and hydrogenation activity of Pt nanosites on the TiN support: Photo-assisted metal-support synergy

The current appeal for sustainable chemistry urgently needs to develop a facile and green method for the synthesis of highly efficient catalysts. Herein, for the first time, a highly skilled catalyst was prepared by photodeposition (PD) of Pt nanosites on the titanium nitride (TiN) under the illumination of Xe lamp in a short period. The resulted Pt/TiN-pd had uniformly dispersed particle sizes (∼2.2 nm) and a high reduction degree, which exhibited high phenol conversion (641 mol/molPt h and cyclohexanone selectivity (∼82 %) under mild reaction conditions (50 °C and 0.5 MPa). Characterizations by the XRD, XPS, DRUV-vis, HRTEM, etc., have revealed the intensified metal-support synergy assisted by the photo-irradiation. It not only facilitated the close contact between Pt species and TiN support to constrain the metal sintering but also promoted their charge transfer as a result of the surface plasmon resonance effect. This simple strategy of photodeposition noble metals on TiN affords a time-saving and structure-tunable alternative to attain highly efficient catalysts for sustainable chemical transformation.

Highly Efficient Phenol Hydrogenation to Cyclohexanone over Pd@CN-rGO in Aqueous Phase

Selective hydrogenation of phenol is a green strategy to produce cyclohexanone. Achieving high phenol conversion and cyclohexanone selectivity under mild conditions is a significant challenge in th...

Preparation of solar/visible-light active TiO2 photocatalysts with carboxylic acids for the degradation of phenol

TiO2 catalysts were synthesized via simple sol–gel method using different carboxylic acids. The synthesized materials were characterized by UV–Vis spectroscopy (DRS), X-ray diffraction (XRD), N2 physisorption and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the samples was evaluated in the degradation of phenol under visible and solar light. The prepared catalysts using the carboxylic acids showed an improvement in the characteristics of TiO2. Particularly, the catalyst prepared with citric acid, showed a single pure anatase phase with a small crystallite size (of around 9.4 nm), larger surface area (81 m2/g) and narrower band gap (2.94 eV) compared to the non-modified TiO2 and the reference Degussa P25. Moreover, the results showed that using citric acid, a high conversion of phenol under visible light of around 46% was achieved and a complete degradation under sunlight in a shorter time of around 90 min.

Stability and deactivation of graphene catalyst for phenol degradation in a fixed-bed reactor

Stability and deactivation of paper-like sintered stainless steel fibers-graphene (PSSF-Gr) catalyst for catalytic wet peroxide oxidation (CWPO) of phenol are investigated in a fixed-bed reactor. First, the PSSF-Gr catalyst with three-dimensional structure is synthesized by a chemical vapor deposition (CVD) technique. Then, the effect of residence time on the stability of the PSSF-Gr catalyst is explored by different catalyst bed height. Finally, the deactivation mechanisms of the PSSF-Gr are investigated by SEM, EDS, XRD, Raman spectroscopy, AAS, FTIR, TG, NH3-TPD, CO2-TPD, GC and XPS, respectively. The PSSF-Gr with residence time of 1.46 min exhibits a high phenol conversion (above 90%) after continuously operation for 72 h, but the total organic carbon (TOC) conversion experiences a downward 38 h later. However, when the residence time is increase to 5.84 min, the PSSF-Gr always achieves complete phenol conversion after continuously treatment for 96 h, and the TOC conversion always remains more than 81% within 72 h, but the TOC removal starts to decline 72 h later. After analyzing fresh and these two used PSSF-Gr catalysts, it can be summarized that the deactivation of PSSF-Gr is ascribed to the collapse of PSSF support structure, the change of graphene intrinsic properties, and the deposition of carbonaceous compounds.

Degradation of phenol using mill scale as a Fenton‐type catalyst

AbstractThe oxidation of phenol using mill scale (waste material produced during the hot rolling of steel) as iron source in a type Fenton process was investigated in this work. The mill scale was characterized by XRF, FT‐IR, XRD and SEM. The oxidation tests were carried at 25°C and atmospheric pressure, controlling the pH to 3.7. The phenol conversion and total organic carbon (TOC) removal as a function of catalyst loading (300–1000 mg/L) and phenol concentration (47 and 100 mg/L) were evaluated. The mill scale achieved high conversion of phenol (between 60.8 ± 2.2 and 94.5 ± 2.5%) and mineralization to CO2 (between 38.9 ± 1.2 and 55.6 ± 2.5%) after 4‐h reaction. The mill scale showed a good catalytic performance, even after three cycles of reaction. Therefore, utilizing mill scale as a catalyst of the Fenton process is an alternative to the use of waste in the steel industry.

Liquid Phase Selective Hydrogenation of Phenol to Cyclohexanone over Electrospun Pd/PVDF-HFP Catalyst

Cyclohexanone is an important industrial intermediate in the synthesis of materials such as nylons, but preparing it efficiently through one-step hydrogenation of phenol is hindered by over-reduction to cyclohexanol. Using an efficient catalyst can enhance the selectivity of cyclohexanone at high phenol conversion. In this study, catalysts comprised of palladium nanoparticles supported on electrospun PVDF-HFP (polyvinylidene fluoride-co-hexafluoropropylene) nanofibers were prepared using the electrospinning technique. The catalysts were characterized using thermogravimetric analyzer (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM), and drop shape analyzer (DSA). The prepared catalysts were used to hydrogenate phenol into cyclohexanone in a batch reactor. The Pd/PVDF-HFP catalyst showed a very high product selectivity and high phenol conversion. The conversion of phenol achieved was 98% with 97% cyclohexanone selectivity in 7 h using 15 wt% of palladium (0.0021 moles) relative to phenol (0.0159 moles). The turnover number (TON) and turnover frequency (TOF) values calculated were 7.38 and 1.05 h−1, respectively. This paper presents original research in heterogeneous catalysis using novel electrospun nanofibers. Multiphase hydrogenation of phenol to cyclohexanone over electrospun Pd/PVDF-HFP catalyst has not been reported by any researcher in the literature. This work will also provide a research window for the application of electrospun polymeric nanofibers in multiphase reactions.

Phenol Catalytic Hydrogenation over Palladium Nanoparticles Supported on Metal‐Organic Frameworks in the Aqueous Phase

AbstractMetal‐organic frameworks (MOFs) have been extensively applied as supports in hydrogenation catalysis owing to their topological structure and high hydrogen storage capabilities. Pd nanoparticles (NPs) supported on a hollow box‐shaped MOF were prepared for phenol hydrogenation in the aqueous phase. The MOF preparation modulated by monocarboxylic acids grow into different structures. MOF140‐AA, modulated by acetic acid at 140 °C, presents the structure of regular cube with a smooth surface. Compared to other supports, Pd NPs supported on MOF140‐AA presents high phenol conversion due to the high hydrogen storage capability of MOF140‐AA. Phenol is completely converted to cyclohexanol over Pd/MOF140‐AA reacted at 260 °C for 2 h with high selectivity. The reaction mechanism of phenol hydrogenation is studied by density functional theory (DFT). The phenol hydrogenation mechanism is calculated on a Pd38 cluster, which describes the reaction pathway consistent with experimental results.

Preparation of Cu-ZSM-5 catalysts by chemical vapour deposition for catalytic wet peroxide oxidation of phenol in a fixed bed reactor.

Cu-ZSM-5 catalysts were prepared by chemical vapour deposition for catalytic wet peroxide oxidation (CWPO) of phenol in a fixed bed reactor. Firstly, Cu-ZSM-5 catalysts with Cu loading of 0.5, 2, and 6 wt% were prepared and characterized by X-ray diffraction (XRD), N2 adsorption–desorption and X-ray photoelectron spectra (XPS). The characterization results demonstrated that CuO was uniformly dispersed on ZSM-5 with slight effect on the structure properties of the support. Then, several variables, such as the copper loading, reaction temperature, catalyst bed height and feed flow rate were investigated in the CWPO of phenol in aqueous solution at high concentration (1000 ppm). Compared with the catalyst prepared by the impregnation method, the Cu-ZSM-5 prepared by chemical vapour deposition has a better capacity of further oxidizing the intermediate organic products into carbon dioxide and water with less metal loading. Based on the Cu-ZSM-5 catalyst with Cu loading of 6 wt%, complete removal of phenol and a high TOC reduction (around 70%) have been achieved at the temperature of 80°C feed flow rate of 2 ml min−1 and catalyst bed height of 3 cm. Moreover, this catalyst maintained high catalytic activity after three runs with high phenol conversion (94%) under this optimum operating condition. Finally, the reaction mechanism was studied based on the intermediates detected by high-performance liquid chromatography (HPLC).

Preparation and characterization of lanthanum phosphate catalysts for O-methylation of phenol to anisole in gas phase

Lanthanum phosphate catalysts have been synthesized in 3 different techniques such as (i) simple co-precipitation (LaP-1), (ii) co-precipitation followed by hydrothermal treatment (LaP-2) and (iii) pH variation method (6LaP-3 the prefixed 6 denotes the flocculated pH). Lanthanum and phosphate concentration in all the catalysts is constant (La/P=1) irrespective of method of preparation. All the 3 catalysts (LaP-1, LaP-2 and 6LaP-3) prepared by different methods are used as catalysts for the O-methylation of phenol and found that the catalyst prepared by pH variation method (6LaP-3) exhibited better activity. A series of catalysts with La/P=1 by pH variation method (2LaP-3, 6LaP-3, 9LaP-3 and 12LaP-3) have been prepared and characterized by FT-IR, X-ray diffraction and BET surface area to obtain the structural and textural information. Temperature programmed desorption of NH3 and CO2 studies of LaP-3 catalysts revealed the distribution and strength of acidic and basic sites respectively. LaP-3 catalysts are in hexagonal and rhabdophane phases (XRD). The LaP-3 catalysts are highly active and selective towards formation of anisole via methylation of phenol with methanol in the vapor phase. 2LaP-3 is the best catalyst among the LaP-3 catalyst series in the catalytic activity point of view. Weak and moderate acidic sites along with basic sites might have contributed for the high conversion of phenol and good selectivity of anisole.

Performance of a cell-foam trickle-bed reactor for phenol wet oxidation: Influence of operation parameters and modelling

Abstract The homogeneous wet oxidation of phenol, catalysed by Cu(II), has been studied in a trickle-bed reactor. The reactor bed consisted of a ceramic foam made of alumina with a cell density of 20 ppi. This bed is especially suited to promote mass transfer between phases with very low pressure drop. The gas phase (oxygen at 0.6 MPa) was circulated continuously, while the liquid phase (40 mol/m 3 phenol in water) was circulated in discontinuous mode, i.e. with total recirculation of liquid. The experiments were planned to determine the influence of the main operating conditions, i.e. liquid superficial velocity (0.9–3.3 × 10 −3 m/s), Cu(II) concentration (0.41–0.945 mol/m 3 ) and temperature (110–143 °C). Temperature and liquid superficial velocity were found to have the most marked influence in phenol conversion. The use of the foam packing, particularly at high liquid superficial velocities, enhances oxygen mass transfer between phases and increases the efficiency of the process (higher phenol conversion). A mathematical model, based on conservation equations applied to the bulk liquid and liquid film, has been proposed and validated with the experimental results. It has been found that the model is able to predict the experiments within an error of ±10%.