Wet Air Oxidation Of Phenol Research Articles

Catalytic wet air oxidation of phenol over nano mesoporous lanthanum oxide synthesized by chitosan template method

The study investigates the effectiveness of nano mesoporous lanthanum oxide (La2O3), synthesized by the chitosan template method, as a catalyst for the wet air oxidation of phenol (WAO). To relate the performance of the synthesized La2O3 to its chemical and textural characteristics, it was subjected to a thorough characterization using various analytical techniques, including TG-DTG, XRD, FTIR, BET, TEM, TPD-CO2, TPD-NH3, and H2-TPR. Nanomesoporous La2O3 displayed remarkable efficiency in removing phenol and total organic carbon (TOC) while exhibiting a greater preference towards non-organic compounds. Significant improvement in removal efficiency and selectivity when compared to non-catalytic wet air oxidation is observed for the catalyst. The study investigated the impact of temperature, catalyst dosage, airflow, and phenol pumping rate on the catalytic wet air oxidation (CWAO) of phenol. Even after 6 h of continuous reaction, La2O3 exhibited exceptional catalytic stability. The mesoporous nature and presence of Lewis basic sites in nano-La2O3 may be crucial in facilitating the degradation of phenol and enhancing the efficiency of TOC removal. The study concludes that the chitosan template method is an effective approach for synthesizing nano mesoporous lanthanum oxide, which could be used as a promising catalyst for the treatment of phenol-containing wastewater.

Enhancing electronic metal support interaction (EMSI) over Pt/TiO2 for efficient catalytic wet air oxidation of phenol in wastewater

Phenol is one of the major hazardous organic compounds in industrial wastewater. In this work, a highly active Pt/TiO2 catalyst for catalytic wet air oxidation (CWAO) of phenol was obtained by supporting pre-synthesized Pt on TiO2. During the followed hydrogen reduction, strong hydrogen spillover occurred without the migration of TiO2 onto Pt. The reduced support then enhanced the electron transfer from TiO2 to Pt, increasing the percentage of partially negative Pt (Ptδ-), which has been confirmed by XPS. The strong EMSI made the obtained catalyst far more active than Pt/TiO2 prepared by impregnation method. The electron-enriched Pt/TiO2 achieved total organic carbon (TOC) conversion of 88.8% and TOF 149 h−1 at 100 °C and 2 MPa O2, while conventional Pt/TiO2 gave TOC conversion of 39.5% and TOF 41 h−1 for CWAO of phenol. Our work indicates that the enhancement of EMSI between metal and support can be an effective approach to develop highly active catalysts for phenol treatment.

Synthesis, characterization and activity of W–La/CexZr1−xO2 catalysts in the catalytic wet air oxidation of phenol

Synthesis, characterization and activity of W–La/CexZr1−xO2 catalysts in the catalytic wet air oxidation of phenol

Preparation of CuO/HZSM-5 catalyst based on fly ash and its catalytic wet air oxidation of phenol, quinoline and indole

This work aims to use fly ash and the organic template of tetrapropyl ammonium bromide (TPABr) to synthesize the catalyst carrier of HZSM-5 and prepare the catalyst of CuO/HZSM-5 for catalytic wet air oxidation (CWAO) of phenol, quinoline and indole in aqueous solution. The carrier and the catalyst were characterized by x-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF) and Brunauer-Emmett-Teller (BET) tests and the results indicate HZSM-5 zeolite and CuO/HZSM-5 catalyst have been successfully synthesized. The specific surface area of catalysts with copper loading from 0 to 15% decreased from 310.1 m2 g−1 to 253.8 m2 g−1. The results of catalyst performance showed that the catalyst of CuO/HZSM-5 with copper loading of 10% has the best removal effect on the mixed aqueous solution containing phenol, quinoline and indole. When the total concentrations of phenol, quinoline and indole are 200 mg.l−1 (namely 120 mg phenol·l−1, 60 mg quinoline·l−1 and 20 mg indole·l−1), the catalyst with the copper loading of 10% can remove these organic matters with 100% efficiency after reaction for 4 h at 200 °C and the COD removal rate is more than 75%. Under the same experimental conditions, if the reaction temperature drops to 120 °C, the COD removal rate will rise to 86.2%. The CWAO experiments showed the optimum reaction temperature range for the Cu-10% catalyst is from 120 °C to 150 °C.

Synergistic effect between Mn and Ce for active and stable catalytic wet air oxidation of phenol over MnCeOx

A series of MnCeOx catalysts for the catalytic wet air oxidation (CWAO) of phenol is developed by a redox-precipitation preparation method. Among them, Mn9Ce1Ox (Mn/Ce = 9:1) shows excellent activity and stability which can achieve TOC conversion of 88.1 % in 60 min at 70 °C and retain stable for five consecutive runs. Even at 50 °C, Mn9Ce1Ox can reach a phenol conversion of 84. 2% and a TOC conversion of 73.8 %. The roles of Mn valence state and Ce modification in the catalytic performance of Mn9Ce1Ox are extensively investigated by XRD, BET, Raman, H2-TPR and XPS. It is found that high Mn4+ concentration favors phenol adsorption and oxidation while high Mn3+ concentration favors oxygen activation. Ce optimizes the Mn4+/Mn3+ ratio and thus enhances catalytic activity. Additionally, Ce retains the structure of the catalyst and prevents Mn4+ and Mn3+ from being reduced to Mn2+, which contributes the good stability.

Catalytic wet air oxidation of phenol by cordierite honeycomb washcoated with Al/Zr pillared bentonite in a plug flow reactor

Cordierite monoliths coated with Al/Zr pillared bentonite clay powder were synthesized and tested for catalytic wet air oxidation (CWAO) of phenol aqueous solutions in a plug flow reactor. The catalysts were characterized by using various techniques (EDS, SEM, BET and XRD), confirming the effective deposition of Al/Zr pillared bentonite clay on the channel walls of cordierite monolith. The composite catalyst showed good mechanical stability after ultrasound treatment. The performance of the composite catalyst was evaluated in a catalytic plug flow reactor for continuous oxidation of phenol in terms of catalytic activity as well as their stability. The composite catalyst achieved high catalytic performance (100 % phenol conversion and 91 % total organic carbon reduction) with high stability after 140 h long experiment. During the CWAO of phenol reaction, aromatic ring intermediates (p-benzoquinone, catechol and hydroquinone) and short-chain carboxylic acids (oxalic acid, maleic acid, formic acid, acetic acid and malonic acid) were identified. Kinetic parameters of the model that describes the formation and oxidation of intermediate aromatic compounds and short-chain carboxylic acids were determined. The obtained experimental data results were described sufficiently with respect to phenol conversion. The proposed CWAO of the phenol kinetic model accounts for internal and external diffusion limitations, assuming the pseudo-first-order reaction. Therefore, synthesized monolithic catalysts have great potential for application in CWAO of phenol, since the materials used in the process are inexpensive, abundant and require minimal modifications.

Catalytic wet air oxidation of phenol: Review of the reaction mechanism, kinetics, and CFD modeling

Advanced oxidation processes, specifically catalytic wet air oxidation (CWAO), are considered as useful and robust methods for the treatment of refractory organic compounds such as phenol in wastewater. This paper reviews reaction mechanisms, kinetics and computational fluid dynamics (CFD) modeling of CWAO of phenol. Different reaction mechanisms have been proposed by various researchers to account for possible intermediates during phenol oxidation. These mechanisms can be either direct or indirect; with the indirect path resulting in the formation of intermediates, while with the direct mechanism, no intermediates are formed, the reaction proceeds straight to carbon dioxide and water. Acetic acid is considered as the most stable intermediate of phenol oxidation. Power law and Langmuir–Hinshelwood models were used to account for the adsorption/desorption of the reactants on the surface of the catalyst. The reviewed studies show that phenol conversion increases with increased temperature, pressure, gas velocity and decreases with increasing liquid space velocity. The formation of hot spots next to the walls of the reactor leads to safety issues and may cause catalyst deactivation and reactor thermal run away. This prompted a review of liquid mal-distribution and the formation of hot spots inside the reactor using the CFD modeling technique. In most cases, liquid channeling was observed, resulting in the formation of hot spots and catalyst deactivation.

Synthesis and characterization of nanomesoporous lanthanum aluminate (LaAlO3) for catalytic wet air oxidation of phenol

Nanomesoporous LaAlO3 synthesized by reverse microemulsion method were tested in the catalytic wet air oxidation (CWAO) of phenol in a fixed bed reactor. Synthesized LaAlO3 was characterized in depth by TG-DSC, XRD, FTIR, BET, TEM, TPD-CO2, TPD-NH3, and H2-TPR in order to relate its performances to the chemical and textural characteristics. Nanomesoporous LaAlO3 showed high activity towards phenol and in total organic carbon (TOC) removal with greater selectivity to non-organic compounds, a clear increase in the removal efficiency and selectivity relatively to non-catalytic wet air oxidation being observed. Effect of temperature, catalyst dosage, air flow, and phenol pumping rate in CWAO of phenol was investigated. LaAlO3 displayed high catalytic stability even after 6 h of continued reaction. Structural and textural stability of LaAlO3 was confirmed by XRD and BET surface area analysis of regenerated catalyst. Lewis basic sites and mesoporous nature of nano-LaAlO3 may play an important role in phenol degradation and TOC removal efficiency with high selectivity to non-organic compounds.

Preparation of Cu-Loaded Biomass-Derived Activated Carbon Catalysts for Catalytic Wet Air Oxidation of Phenol

A series of Cu-loaded biomass-derived activated carbon (Cu/AC) catalysts with various impregnation ratios were prepared by precursor impregnation (PI) and activated carbon impregnation (ACI) method...

Influence of operational parameters and kinetic modelling of catalytic wet air oxidation of phenol by Al/Zr pillared clay catalyst.

Single and mixed oxide Al/Zr-pillared clay (Al/Zr-PILC) catalysts were synthesized and tested for catalytic wet air oxidation (CWAO) of aqueous phenol solution under milder conditions, in a semi-batch reactor. The catalysts were synthesized from natural bentonite clay using ultrasonic treatment during the aging and intercalation steps and were characterized using High Resolution Scanning Electron Microscopy-Energy Dispersive angle X-ray spectrometry (HRSEM-EDX), powder X-ray diffraction (p-XRD), nitrogen adsorption/desorption, Fourier Transforms InfraRed Spectroscopy (FTIR) and zeta potential. Successful pillaring of aluminum and zirconium oxides into the clay was confirmed by p-XRD with increased basal spacing (1.92 nm) and higher specific surface area (230 m2/g). The influence of stirrer speed (200-1000 rpm), catalyst dosage (1-3 g/L), initial pH (1-3), initial phenol concentration (500-1500 mg/L), the effect of temperature (80-150 °C) and oxygen pressure (5-15 bar) was evaluated on phenol conversion and their reaction kinetics. At the optimum conditions of initial pH of 3, catalyst dosage of 2 g/L, initial phenol concentration of 1000 mg/L, reaction temperature of 100 °C, and oxygen pressure of 10 bar, the complete removal of phenol was achieved by Al/Zr-PILC within 120 min. The CWAO process was well-described by the first-order power rate law kinetics model. The apparent activation energy of the reaction calculated by Arrhenius equation was 21.306 kJ/mol.

Kinetic study of phenol oxidation in a trickle bed reactor over Al/Zr-pillared clay catalyst

Catalytic wet air oxidation of phenol was studied in a trickle bed reactor operated at 10 bar and temperatures between 120-160 °C over pillared clay wash-coated monolith catalyst. Different variables were studied including reaction temperature and liquid flow rate. The obtained results indicated that phenol conversion increase with an increase in temperature, whereas an increase in liquid flow rate has a negative effect on phenol conversion. Simple power law was used to model the kinetics of the process. When a simple power law model was used experimental results were predicted successfully with R2 = 0.9988 at 160 °C and the activation energy was 42.289 kJ/mol.

Process intensification in catalytic wet air oxidation of phenol via coupling gas‐liquid microdispersion with trickle bed reactors

AbstractIntensified trickle bed reactors were developed for catalytic wet air oxidation (CWAO) of phenol, by generating microbubbles before gas/liquid fluid flows along catalyst packed‐beds. By coupling gas‐liquid microdispersion module, phenol disappearance rate significantly increases under the same operating conditions and phenol conversion reaches 92% in 22 seconds at 160°C and 1000 kPa. Effects of operating conditions were studied systematically and results demonstrated characteristics of high‐interaction regime at low Reynolds number. Comparison of effects among mass transfer and reaction steps shows CWAO reaction is controlled by resistance to liquid‐solid mass transfer of phenol in most cases, while gas‐liquid mass‐transfer‐resistance is ignorable. A dimensionless correlation, Sh = 2.29φ−0.91(ReL + ReG)0.04, was established, by considering influences of liquid film thickness and fluid flow situations on liquid‐solid mass transfer coefficient in microbubble‐in‐liquid/catalyst‐particle system. The study would provide an effective method for intensifying CWAO and other liquid‐solid‐mass‐transfer‐resistance‐controlled gas/liquid/solid catalytic reactions and help understand mass transfer mechanism in new gas/liquid/solid system.

Catalytic wet air oxidation of phenols over porous plate Cu-based catalysts

Catalytic wet air oxidation (CWAO) of phenol has attracted much attention because of its high versatility and remarkable economy-scale advantages. In this submission, a series of M3-Al-500 catalysts (with M = Cu, Mn, Fe, Ni, Zn and Co) were prepared via controlled calcination of layered double hydroxides, and tested in the CWAO of high concentrated phenol (2.1 g/L) with air under mild condition (120 °C and 1.0 MPa). It was found that Cu3-Al-500 was the most active among these tested catalysts as phenol converted completely within 2 h. Characterizations indicated that the performance of Cu-based catalyst could be attributed to the redox transitions of Cu2+/Cu+ and/or the formation of H2O2 in reaction mixture. At the same time, the surface acidity of Cu3-Al-500 can also accelerate the degradation of phenol. The possible degradation mechanism of phenol over Cu-based catalyst was proposed.

Performance enhancement of trickle bed reactor for the removal of organic compounds from petroleum industrial wastewater

Catalyst Wet Air Oxidation of phenol Promoted with Hydrogen Peroxide (PP-CWAO) was studied experimentally in this work using a trickle bed reactor operating in both steady state and periodic operation (liquid flow modulation). The effect of cyclic parameters (cycle period and split) are investigated under the same conditions chosen on the basis of the steady state results for PP-CWAO. The results showed that the PP-CWAO of phenol are kinetically controlled for steady state operation. For periodic operation, the time average conversion enhancement is indeed quite considerable in liquid flow modulation as split is lowered from steady state cycle split (σ = 1) to a value of (σ = 0.5) and reached as much as 6.66 % over the steady state at cycle period (τp) = 15 sec.

Direct low-temperature hydrothermal synthesis of uniform Pd nanoparticles encapsulated mesoporous TS-1 and its excellent catalytic capability

A simple and direct low-temperature hydrothermal synthesis approach (100 °C) has been developed to encapsulate Pd nanoparticles (ca. 2.3 nm) within nano-sized mesoporous TS-1 zeolite by utilizing dichloro(ethylenediamine)palladium (DEAP) and cetyltrimethylammonium bromide (CTAB) as palladium source and mesoporogen, respectively. It's demonstrated that the aging process of the mother liquid and low-temperature hydrothermal treatment can effectively inhibit the premature precipitation of metal precursor and thus the successful encapsulation of Pd nanoparticles into mesoporous TS-1 nanocrystals, so that the frequently occurring of Pd nanoparticle aggregation at high temperature was expectedly avoided. Consequently, the as-synthesized catalysts with highly thermal stability and mesoporous channels exhibit excellent catalytic activity and recyclability in the oxidation of CO with relatively low Pd content (0.53 wt% Pd) and catalytic wet air oxidation of phenol (66.2% of phenol conversion, 100 °C).

Catalytic Wet Air Oxidation (CWAO) of Phenol in a Fixed Bed Reactor Using Supported Ru and Ru‐Au Catalysts: Effect of Gold and Ce Loading

AbstractCatalysts of Ru and Ru−Au prepared by the wet impregnation and Deposition‐Precipitation methods supported on ZrO2 modified by CeO2(10 and 20 wt%) synthetized by sol‐gel method, in order to study Au and CeO2 addition effect in the catalytic wet air oxidation of phenol, carried out in an automatized continuous fixed‐bed reactor using oxygen as an oxidizing source. Characterizations of the catalysts were made by X‐ray Diffraction (XRD), Specific Surface Area (BET), X‐ray Photoelectron Spectroscopy (XPS), Transmission Electronic Microscopy (TEM), Scanning Electronic Microscopy (SEM), Ultraviolet–visible Spectroscopy (UV‐vis) and Temperature Programmed Desorption of Ammonia (NH3‐TPD). The effect of Au is reflected in the selectivity to CO2 of the catalysts Ru‐ZrO2 and Ru−Au‐ZrO2 with the increase in selectivity from 89 to 95% related to the increase in acidity which increases from 70 to 102 (μmol of NH3/ gCat). Ce loading effect in this case was important to the enhance the CO2 selectivity explained by the formation of Ce4+‐O2−‐M that could favor the oxygen transfer between the catalyst surface and the adsorbed species by a redox mechanism.

A Novel Synthesis Method of Al/Cr Pillared Clay and its Application in the Catalytic Wet Air Oxidation of Phenol

Natural bentonite clay was pillared with Al and Cr polycations (Al-PILCs and Cr-PILCs) as well as with both Al and Cr mixed polycations (Al/Cr-PILCs) at different Al/Cr molar ratios. The structural and textural properties of the pillared clay catalysts were characterized by various techniques, such as high resolution scanning electron microscopy with energy dispersive system, powder X-ray diffraction, adsorption–desorption of N2 at − 196 °C, Fourier transform infrared spectroscopy, thermogravimetric analysis, cation exchange capacity and zeta potential. The obtained results showed that the intercalation of polycations in the interlamellar space of clay led to changes in the clay properties, basal spacing and specific surface area of a mixed PILCs were higher compared to single PILCs. Moreover, diffractograms of the Cr-PILCs confirmed the presence of a Cr2O3 phase. The catalytic wet air oxidation (CWAO) of the phenol was studied in a batchwise slurry reactor, at the experimental conditions of 100 °C temperature, 10 bar oxygen (O2) partial pressure, at pH 3.0, 100 mg/L concentration and 0.4 g of catalyst. All catalysts were analysed to determine the conversion of phenol and removal of total organic carbon (TOC). The results showed that, Al-PILCs displayed higher removal of phenol and TOC conversion than Cr-PILCs. In the case of mixed Al/Cr-PILCs, maximum removal values of phenol and TOC conversion were achieved with Al/Cr molar ratio of 1:1. Moreover, aromatic intermediate products as catechol, hydroquinone and benzoquinones which are identified in the beginning of the phenol oxidation oxidized into short-chain carboxylic acids such as oxalic acid, maleic acid, formic acid, acetic acid and malonic acid. The obtained results demonstrate the potential of Al/Cr-PILCs catalyst as robust and cheap catalyst for CWAO of phenol under mild reaction conditions.

Catalytic wet air oxidation of phenol over carbon nanotubes: Synergistic effect of carboxyl groups and edge carbons

It has been widely documented that the oxygen-containing functionalities, especially carboxyl groups, on carbon surfaces play crucial roles in the catalytic wet air oxidation (CWAO) reactions. Herein, the CWAO of phenol with molecular O2 as terminal oxidant using cylindrical and herringbone carbon nanotubes (CNTs) underwent different treatments as catalysts were conducted in batch mode. It was uncovered that the catalytic function of carboxyl groups strongly depended on the structure of CNTs. Parallel CNTs (p-CNTs) with cylindrical graphitic walls displayed the highest catalytic activity after nitric acid oxidation, due to the carboxylated carbon debris (CDs) coating on surfaces. For herringbone CNTs (h-CNTs), carboxyl groups are mostly linked to its sidewalls, where abundant edge carbons were exposed, providing an enhanced CWAO activity. The positively synergistic effect of carboxyl groups and adjacent edge carbons was responsible for the activation of O2, leading to the improved CWAO activity. This study provides a new insight into the structural effect of carbon materials on the CWAO of phenol.

Каталитическое жидкофазное окисление фенола кислородом воздуха в присутствии катализаторов высокодисперсного рутения, нанесенного на углеродные нанотрубки

Каталитическое жидкофазное окисление фенола кислородом воздуха в присутствии катализаторов высокодисперсного рутения, нанесенного на углеродные нанотрубки

Synthesis and characterization of an efficient and stable Al/Fe pillared clay catalyst for the catalytic wet air oxidation of phenol.

A facile method for synthesizing Al/Fe pillared clays (PILCs) from natural bentonite clay, by using ultrasonic treatment during the aging and intercalation steps, has been established. Single metal (Fe-PILCs and Al-PILCs) and mixed metal (Al/Fe-PILCs, with varying compositions of the pillaring precursors) pillared clays were prepared and characterized with a combination of chemical and instrumental methods. The pillared clays were evaluated as catalysts in the catalytic wet air oxidation (CWAO) of phenol and the mixed metal pillared clay catalysts, especially with an Al/Fe ratio of 3 : 1, were found to be highly active and stable, with superior properties such as surface areas, basal spacing, high porosity and thermal stability. The catalysts could also be reused several times without significant loss of activity. The results of the study show that Al/Fe-pillared clay catalysts are effective catalysts for the oxidation of phenol and removal of TOC in aqueous solutions. The main intermediate products in the CWAO of phenol were hydroquinone, pyrocatechol, and benzoquinone and oxalic, formic, malonic, oxalic, malonic and maleic acids.