Catalytic wet oxidation: micro–meso–macro methodology from catalyst synthesis to reactor design

Abstract

Compared to alternative mature wet oxidation technologies that have tremendously proliferated in industry, heterogeneously mediated catalytic wet oxidation (CWO) has achieved, thus far, poor commercial penetration. The two factors that are likely responsible for this situation are (i) the lack of efficient and robust catalysts that pass with success the acid-test for commercial exploitation remote from the aseptic academic conditions, (ii) and the lack of a comprehensive reactor design framework and methodology for scale-up, reactor selection and operation inherent to the multiphase nature of the CWO reactors. This synthetic review summarizes the recent research and development work conducted at Laval University on the CWO from both the perspectives of catalyst development and testing, and multiphase reactor simulations and selection. Specific emphasis was put, on the one hand, on the development brought to some manganese oxide-ceria composites against deactivation, and on the other hand, on the formulation of multidimensional unsteady-steady non-isothermal mass-energy transport/reaction models, embedding catalyst deactivation or not, for trickle bed reactors, packed bubble column reactors, three-phase fluidized beds and slurry bubble columns. A micro-Meso-macro scale methodology was adopted from the materials synthesis up to reactor selection in which the catalyst performance (conversion, selectivity, and deactivation), the intrinsic chemical kinetics, the fluid phase thermodynamics, the pellet scale transport, and the reactor scale physical phenomena (heat, mass transport and hydrodynamics) were integrated. As a result, several aspects relevant to reactor behaviour such as solvent evaporation due to CWO reaction exothermic effects, catalyst partial wetting and catalyst deactivation, and back-mixing effects were covered, and recommendations were formulated. NomenclatureA reactor cross-sectional area, m 2 C concentration, mol/m 3 or g/L C p isobaric specific heat capacity, J/kg/K D eff effective diffusivity, m 2 /s E activation energy, kJ/mol E z axial dispersion coefficient, m 2 /s H Henry constant, or bed height, m H j hidden layer transfer function, k rate constants, mol/min/kg cat. (equations (1)-Arrhenius pre-exponential factor, mol/min/kg cat. equation (9) ka ll liquid-liquid volumetric mass transfer coefficient. s )1 k l a gas-liquid volumetric mass transfer coefficient, s )1 ka sls liquid-solid mass transfer coefficient, s )1 K adsorption equilibrium constant, m 3 /mol L v water enthalpy of vaporization, J/mol [m c ] catalyst loading, kg cat./m 3 P pressure, atm r spherical co-ordinate at pellet scale, m r c chemical reaction rate, mol/m 3 /s S neural network output S M mineralization selectivity t time, min T absolute temperature, K U i neural network inputs U superficial velocity, m/s v molar volume, cm 3 /mol [W] carbonaceous deposit carbon concentration, mol C/m 3 solution x dissolved mole fraction X chemical conversion y gas mole fraction z longitudinal co-ordinate, mGreek a deactivation function, DH...

Cério: propriedades catalíticas, aplicações tecnológicas e ambientais

“…Além dessa função reguladora de oxigênio, a presença de CeO 2 também evita que os catalisadores CTV percam a eficiência em altas temperaturas, pois ela inibe/ desloca as transições de fase de outros materiais como, por ex., do suporte de alumina 16,19,22 . A adição de íons lantânio, zircônia, BaO e SiO 2 à estrutura do CeO 2 pode contribuir para aumentar a quantidade de defeitos na rede cristalina e proporcionar ao CeO 2 maior capacidade para armazenar oxigênio 22,[27][28][29][30][31][32][33]35,38,[42][43][44][45] , melhorando o desempenho dos catalisadores CTV. Atualmente, o uso de CeO 2 neste tipo de catalisador é uma das principais aplicações tecnológicas deste elemento e tem consumido a maior parte do cério produzido mundialmente 4,6 .…”

Catalytic behaviour and copper leaching of Cu0.10Zn0.90Al1.90Fe0.10O4spinel for catalytic wet air oxidation of phenol

“…Different methods for treating these wastewaters have been widely reported [1,2], and particular attention has been devoted to the catalytic wet air oxidation (CWAO) process [3]. Although the development of inexpensive and efficient solid catalysts used in CWAO is of great interest and many supported or unsupported metal oxides such as Fe/C [4], Cu−Zn−Al−O [5], Cu−Cr−Al−O [6] and Mn−Ce−O [7] have been tested, the threat of catalyst deactivation by polymer deposition and leaching of active compounds has emerged as a major drawback.…”

Catalytic properties of carbon materials for wet oxidation of aniline

“…The quest for highly efficient catalysts was always a main research objective in the studies devoted to CWAO. Heterogeneous catalysts presenting high activity and stability have been investigated over the years [5][6][7][8], since they can be easily removed by filtration from the treated solution. Good catalytic systems, especially supported noble metal catalysts, were used for the oxidation of model compounds (mainly phenol and carboxylic acids) as well as the oxidation of waste waters [9][10][11][12].…”