Modelling of fixed bed catalytic reactors catalyst poisoning

Markoš, Jozef; Brunovská, Alena; Ilavský, Ján

doi:10.1135/cccc19852228

Cited by 2 publications

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“…where C 0 -initial total organic carbon concentration in aqueous phase, mol/l. Catalytic activity (A) of the test catalyst samples in organic carbon mineralization during 4-NP ozonation was calculated as ratio of effective mineralization rate constants with and without a catalyst under equal conditions [6]:…”

Section: Methodsmentioning

confidence: 99%

Catalytic Ozonation of 4-Nitrophenol in the Presence of Magnetically Separable Titanium Dioxide – Magnetite Composite

Kazakov¹,

Vol'khin²,

Kaczmarski³

et al. 2016

Eur Chem Tech J

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This paper deals with determining catalytic activities of titania (TiO2) with various crystalline structures and magnetite (Fe3O4) during mineralization of 4-nitrophenol in aqueous media by ozonation. Among the titania samples under study, amorphized TiO2 was shown to have the highest catalytic activity, while magnetite was characterized by the lowest catalytic activity. A procedure is proposed to synthesize a magnetically separable composite (TiO2/Fe3O4) including amorphized titania and magnetite phases, which involves deposition of a catalytically active titania phase on preformed magnetite particles. We also studied the effect of mass ratio of titania and magnetite phases in the composite on its catalytic activity during 4-nitrophenol mineralization by ozonation. It was found that catalytic activity of composite increased as the amorphized titania phase was doped with magnetite phase up to 30% wt but as the magnetite portion in the composite catalyst was further increased, its activity decreased. According to Fourier transform infrared (FTIR) spectroscopy, content of catalytically active sites (hydroxyl groups of titania) in the composite catalyst decreases as compared to the pure phase of amorphized titania. Increase in catalytic activity of the composite as its magnetite content increases to 30% wt can be attributed to increase of accessibility of catalytically active sites (OH groups) for ozone, because specific surface area and total pore volume of the composite catalyst as determined by BET increase as compared to amorphized TiO2 and catalytically active titania phase is located mostly on surface of magnetite particles which is indicated by scanning electron microscopy (SEM) results and electrophoretic light scattering (ELS) data. It was shown that the obtained composite catalyst of optimized composition, in spite of its fine particles, can be easily recovered from aqueous phase by magnetic field and used repeatedly in ozonation in order to promote water purification process.

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Section: Methodsmentioning

confidence: 99%

Catalytic Ozonation of 4-Nitrophenol in the Presence of Magnetically Separable Titanium Dioxide – Magnetite Composite

Kazakov¹,

Vol'khin²,

Kaczmarski³

et al. 2016

Eur Chem Tech J

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“…Studies based on a (Fickian) second-order partial differential equation with a linear dependence on the concentration(s) account for behavior in the near-equilibrium regime. Far-fromequilibrium phenomena (rate oscillations, spatial-temporal patterns and chaos) have been modelled by considering a nonlinear dependence on the relevant concentration(s) [4]. As for lattice models, the main focus has been on simulations, principally Monte Carlo studies on planar lattices.…”

Section: Introductionmentioning

confidence: 99%

Competing reaction processes on a lattice as a paradigm for catalyst deactivation

Abad

Kozak

2015

Phys. Rev. E

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We mobilize both a generating function approach and the theory of finite Markov processes to compute the probability of irreversible absorption of a randomly diffusing species on a lattice with competing reaction centers. We consider an N-site lattice populated by a single deep trap, and N − 1 partially absorbing traps (absorption probability 0 < s < 1). The influence of competing reaction centers on the probability of reaction at a target site (the deep trap) and the mean walk length of the random walker before localization (a measure of the reaction efficiency) are computed for different geometries. Both analytic expressions and numerical results are given for reactive processes on two-dimensional surfaces of Euler characteristic = 0 and = 2. The results obtained allow a characterization of catalyst deactivation processes on planar surfaces and on catalyst pellets where only a single catalytic site remains fully active (deep trap), the other sites being only partially active as a result of surface poisoning. The central result of our study is that the predicted dependence of the reaction efficiency on system size N and on s is in qualitative accord with previously reported experimental results, notably catalysts exhibiting selective poisoning due to surface sites that have different affinities for chemisorption of the poisoning agent (e.g., acid zeolite catalysts). Deviations from the efficiency of a catalyst with identical sites are quantified, and we find that such deviations display a significant dependence on the topological details of the surface (for fixed values of N and s we find markedly different results for, say, a planar surface and for the polyhedral surface of a catalyst pellet). Our results highlight the importance of surface topology for the efficiency of catalytic conversion processes on inhomogeneous substrates, and in particular for those aimed at industrial applications. From our exact analysis we extract results for the two limiting cases s ≈ 1 and s ≈ 0, corresponding respectively to weak and strong catalyst poisoning (decreasing s leads to a monotonic decrease in the efficiency of catalytic conversion). The results for the s ≈ 0 case are relevant for the dual problem of light-energy conversion via trapping of excitations in the chlorophyll antenna network. Here, decreasing the probability of excitation trapping s at sites other than the target molecule does not result in a decrease of the efficiency as in the catalyst case, but rather in enhanced efficiency of light-energy conversion, which we characterize in terms of N and s. The one-dimensional case and its connection with a modified version of the gambler's ruin problem are discussed. Finally, generalizations of our model are described briefly.

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Modelling of fixed bed catalytic reactors catalyst poisoning

Cited by 2 publications

References 0 publications

Catalytic Ozonation of 4-Nitrophenol in the Presence of Magnetically Separable Titanium Dioxide – Magnetite Composite

Catalytic Ozonation of 4-Nitrophenol in the Presence of Magnetically Separable Titanium Dioxide – Magnetite Composite

Competing reaction processes on a lattice as a paradigm for catalyst deactivation

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