Catalytic Wet Peroxide Oxidation Of Phenol Research Articles

Copper and iron-based monolithic catalysts for phenol Catalytic Wet Peroxide Oxidation (CWPO): Support and iron effects on the catalytic performance

Water is an invaluable resource of our planet, and our lives and those of the future generations rely on it. Phenolic compounds are part of many industries effluents and they are highly toxic and not biodegradable. Therefore, they could be eliminated from water through the Catalytic Wet Peroxide Oxidation (CWPO) reaction. In this work, alumina-supported and cordierite-supported copper and iron-based monolithic catalysts were synthesized and tested in the CWPO of phenol. These structured catalysts were characterized by stereoscopic microscopy, N2 adsorption, XRD, LRS, SEM/EDX and XPS, and their mechanical resistance was analyzed. The effect of both, the support and the presence of iron as a co-active phase on the metal species leaching, and therefore on the catalytic performance, were evaluated. Alumina-supported copper species were more accessible and reducible than cordierite-supported ones and, as a consequence, these rapidly converted the totality of phenol and achieved high mineralization and COD reduction. On the other hand, iron addition as a co-active phase decreased copper leaching in all cases due to Cu-Fe interactions. The bimetallic alumina-supported catalyst exhibited the best catalytic performance with low copper and iron leachings. Consequently, it was tested in a more complex reaction media (tap water). This catalyst resulted promising, converting all the phenol with high mineralization and COD reduction, although suffering some copper and iron leaching.

Calcination temperature effects on the physicochemical properties of copper-based wire-meshes: The implications in the CWPO of phenol

This work investigates phenol elimination from water through the Catalytic Wet Peroxide Oxidation (CWPO) reaction using CuO/TiO2-ZrO2 supported on wire-meshes, all with 5 wt.% Cu and calcined at different temperatures. These were characterized by SEM/EDX, elemental mappings, XRD, LRS and XPS, and their mechanical stability was studied. The increment in the calcination temperature generated less reducible Cu2+ species, which impacted in phenol conversion rate, slowing it down. Particularly, when the lower temperatures were applied (500 – 800 °C), copper was found well-distributed on the support and high mineralization values (above 85%) were obtained. Nevertheless, these high TOC conversions were the result of elevated copper leaching (∼ 40 ppm), markedly contributing as a homogeneous catalyst. Contrarily, the application of more extreme temperatures, such as 850 and 900 °C, led to the migration of copper to the inner part of the coating, and consequently to lower copper leaching (7.6 and 0.9 ppm, respectively), due to a protective effect of the support. Accordingly, the corresponding mineralization degrees were lower, 60 and 40%, respectively. An adequate temperature was found (850 °C), with higher mineralization and better mechanical resistance than the catalyst calcined at 900 °C.

Cu(II) impregnated clay-derived HS zeolite: Synthesis, characterization and catalytic activity on catalytic wet peroxide oxidation (CWPO) of phenol

The majority of phenol-containing liquid industrial wastes are discharged into natural waters. As a result, several investigations, such as catalytic wet peroxide oxidation (CWPO), have been conducted to remediate these effluents. Copper-supported heterogeneous catalysts were prepared by an impregnation technique and tested in CWPO of phenol. Both the raw pyrophyllite clay and its zeolite form were used as supports. The samples were characterized by BET specific surface area analysis, X-ray diffraction, X-ray fluorescence, and X-ray photoelectron spectra. The effect of temperature (25–70 °C), the concentration of hydrogen peroxide (2–10 mmol·L−1), and the amount of catalyst (0.5–3 g·L−1) were selected for optimization of the catalytic system H2O2-2.5% Cu/ZP using the response surface methodology based on central composite design. The catalyst (2.5% Cu/ZP), with support of synthesized hydroxysodalite zeolite form, showed the best catalytic activity in comparison to that based on raw pyrophyllite support (2.5% Cu/RP). The maximized degradation was 100% after 4 h at optimum conditions (T = 50 °C, [H2O2] = 6.39 mmol·L−1, catalyst amount = 1.82 g·L−1) with 87.73% of mineralization.

Simulation and Optimization of the CWPO Process by Combination of Aspen Plus and 6-Factor Doehlert Matrix: Towards Autothermal Operation

This work aims to present an industrial perspective on Catalytic Wet Peroxide Oxidation (CWPO) technology. Herein, process simulation and experimental design have been coupled to study the optimal process conditions to ensure high-performance oxidation, minimum H2O2 consumption and maximum energetic efficiency in an industrial scale CWPO unit. The CWPO of phenol in the presence of carbon black catalysts was studied as a model process in the Aspen Plus® v11 simulator. The kinetic model implemented, based on 30 kinetic equations with 11 organic compounds and H2O2 involvement, was valid to describe the complex reaction network and to reproduce the experimental results. The computer experiments were designed on a six-factor Doehlert Matrix in order to describe the influence of the operating conditions (i.e., the different process temperatures, inlet chemical oxygen demands, doses of H2O2 and space time) on each selected output response (conversion, efficiency of H2O2 consumption and energetic efficiency) by a quadratic model. The optimization of the WPO performance by a multi-criteria function highlighted the inlet chemical oxygen demand as the most influential operating condition. It needed to have values between 9.5 and 24 g L−1 for autothermal operation to be sustained under mild operating conditions (reaction temperature: 93–130 °C and pressure: 1–4 atm) and with a stoichiometric dose of H2O2.

Low-cost iron-doped catalyst for phenol degradation by heterogeneous Fenton

The aim of this work was to study the feasibility of textile sludge as a precursor to prepare catalysts for catalytic wet peroxide oxidation (CWPO) by chemical and thermal treatments. Textile sludge was characterized by physical-chemical and metal composition analyses. The chemical activation was evaluated using iron sulfate and the thermal treatment was carried out at 720 °C in a vacuum pyrolysis reactor. Two catalysts with iron contents of 1.5% and 5.6% were selected. Process parameters influence on CWPO of phenol were evaluated and a maximum removal of phenol and TOC was observed at pH 3 and 60 °C, using 3 g L−1 of the catalyst containing 5.6% of iron and 11.8 mmol L−1 of H2O2. Metal analysis indicated that the textile sludge is suitable to be employed as both iron catalyst and adsorbent. The catalysts characterization indicated a reasonable surface area with a well-developed microporosity and the presence of Hematite structures in the carbonaceous matrix. The degradation process achieved 98.2% of phenol conversion, 68.2% of mineralization and 2.11 mg L−1 of iron leaching in 150 min of reaction. The catalyst presented activity for up to 5 cycles of use, but with loss of efficiency.

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).

Selectivity of hydrogen peroxide decomposition towards hydroxyl radicals in catalytic wet peroxide oxidation (CWPO) over Fe/AC catalysts

Two Fe/AC catalysts prepared with different iron precursors (iron nitrate and iron pentacarbonyl) and the same AC support have been tested in H(2)O(2) decomposition in presence and absence of methanol, a known strong scavenger of hydroxyl radicals, to investigate the selectivity towards .OH formation in this reaction and their behavior in the CWPO of phenol. The catalyst prepared with iron nitrate, with the most oxidized surface and the highest Fe surface content, seems to favor a higher selectivity towards .OH formation in CWPO allowing for complete phenol conversion and a significant TOC removal, with the highest mineralization degree at 50 degrees C and atmospheric pressure. Fe/AC catalysts were more efficient in the CWPO of phenol than in methanol presence due to a better use of the oxidant since adsorbed phenol on catalyst surface minimizes inefficient H(2)O(2) decomposition to H(2)O and O(2)(g). The influence of the initial H(2)O(2) concentration on phenol oxidation with this catalyst was also studied. A theoretical stoichiometric amount of H(2)O(2) for complete oxidation of phenol was chosen as the best starting concentration since auto-scavenging reactions can be minimized and it is sufficient for oxidizing phenol and the aromatic intermediates.