Suchergebnisse

Three-dimensional (3D) Fe/SiC monoliths with parallel interconnected channels and different cell geometries (square, troncoconical, and triangular) were manufactured by robocasting and used as catalytic reactors in hydroxylation of phenol using hydrogen peroxide to produce dihydroxybenzenes; the reaction was performed at Cphenol,0 = 0.33 M, Cphenol,0:CH2O2,0 = 1:1 M, WR = 3.7 g, T = 80-90 °C, and τ = 0-254 gcat·h·L-1 with water as a solvent. The values of the apparent kinetic rate constants demonstrated the superior performance of the triangular cell monoliths for hydrogen peroxide decomposition, phenol hydroxylation, and dihydroxybenzene production reactions. A computational fluid dynamic model was validated with the experimental results. It demonstrated that the triangular cell monoliths, with a lower channel hydraulic diameter and not-facing interconnections, provided a higher internal macrotortuosity that induced an oscillating flow of the liquid phase inside the channels, leading to an additional transverse flow between adjacent parallel channels. This behavior, not observed in the other two geometries, resulted in a better overall performance ; The authors thank the financial support by the Community of Madrid through the project S2018/EMT-4341 and the Government of Spain through the projects: PGC2018- 095642-B-I00 and RTI2018-095052-B-I00 (MCIU/AEI/ FEDER, UE). Also, G. Vega acknowledges the Universidad Autónoma de Madrid for the predoctoral contract

[EN] Three-dimensional (3D) Fe/SiC monoliths with parallel interconnected channels and different cell geometries (square, troncoconical, and triangular) were manufactured by robocasting and used as catalytic reactors in hydroxylation of phenol using hydrogen peroxide to produce dihydroxybenzenes; the reaction was performed at Cphenol,0 = 0.33 M, Cphenol,0:CH2O2,0 = 1:1 M, WR = 3.7 g, T = 80-90 °C, and τ = 0-254 gcat·h·L-1 with water as a solvent. The values of the apparent kinetic rate constants demonstrated the superior performance of the triangular cell monoliths for hydrogen peroxide decomposition, phenol hydroxylation, and dihydroxybenzene production reactions. A computational fluid dynamic model was validated with the experimental results. It demonstrated that the triangular cell monoliths, with a lower channel hydraulic diameter and not-facing interconnections, provided a higher internal macrotortuosity that induced an oscillating flow of the liquid phase inside the channels, leading to an additional transverse flow between adjacent parallel channels. This behavior, not observed in the other two geometries, resulted in a better overall performance. ; The authors thank the financial support by the Community of Madrid through the project S2018/EMT-4341 and the Government of Spain through the projects: PGC2018-095642-B-I00 and RTI2018-095052-B-I00 (MCIU/AEI/FEDER, UE). Also, G. Vega acknowledges the Universidad Autónoma de Madrid for the predoctoral contract.

[EN] Hexagonal boron nitride (h-BN) has been explored as a catalyst for degrading persistent organic pollutants in wastewater by Catalytic Wet Peroxide Oxidation (CWPO). Herein, the superior activity of the h-BN on the phenol degradation (model pollutant) compared to other metal-free catalysts, such as carbon-based ones, and the lower selectivity to CO encourage the potential application of h-BN catalysts in CWPO processes. Through a combined density functional theory calculations, experimental reactions and catalyst characterization approach, a comprehensive study on the reaction mechanism has been conducted. According to this, only defected B atoms in the h-BN layer, protonated as B-(OH), decompose the hydrogen peroxide into highly reactive hydroxyl radicals. The radical species diffuse towards inner h-BN regions and react with the phenol adsorbed by π-π interaction on the h-BN surface. Oxidation by-products cause carbonaceous deposits and progressive deactivation of the h-BN catalyst that can be directly regenerated by burning off in air. ; The authors thank the financial support by the Community of Madrid and the Government of Spain through the projects: S2018/EMT- 4341 and RTI2018-095052-B-I00 (MCIU/AEI/FEDER, UE), respectively. The work done at the University of Sevilla was funded by Spanish Ministerio de Ciencia e Innovación and EU-FEDER, grant PID2019-106871 GB-I00, and the Junta de Andalucía-FEDER, grant: US-1381410. Also, G. Vega acknowledges the Community of Madrid for the Predoctoral contract PEJD-2018-PRE/AMB-9019, co-financed by the European Social Fund through the Youth Employment Operational Program and the Youth Employment Initiative (YEI) 2018. J. Carbajo thanks the financial support by the Government of Spain for a grant under the Juan de la Cierva_Incorporación programme (IJCI-2017- 32682). The authors would like to thank A. Pérez for performing the BET and TGA measurements.