Modeling of Autocyclic Reactor for the Removal of Unburned Methane from Emissions of Natural Gas Engines

Zanoletti, Massimiliano; Klvana, D.; Kirchnerová, J.; Perrier, Michel

doi:10.1021/ie900701h

Cited by 6 publications

(4 citation statements)

References 22 publications

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“…As part of our research to develop a new postcombustion catalytic convertor, we have attempted to develop a highly active palladium-based catalyst for methane oxidation at temperatures <650 C. [34][35][36] Thus, we prepared several combustion catalysts using Pd as the active phase and different metal oxides as support, and we tested them in terms of apparent activity and specific surface. The aim of this work was to compare the performance of Pd on different supports in the total oxidation of methane, trying to relate their performances to the different supports used during the tests (Al 2 O 3 , ZrO 2 , and TiO 2 ).…”

Section: Introductionmentioning

confidence: 99%

Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

2020

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The support effect on the low temperature catalytic oxidation of methane over palladium catalysts was studied by comparing a series of metal oxides as the support. Samples of 0.010 g/g Pd catalysts supported on different grades and/or phases of TiO2, Al2O3, and ZrO2 were prepared via incipient impregnation and their catalytic activity was evaluated using a laboratory plug‐flow reactor. The specific surface area of the supports determined by nitrogen adsorption varied from about 13‐220 m2/g. Initial experiments conducted with titania (anatase) as a support showed a low apparent activity and a poor thermal stability. Focusing on anatase, we have successfully improved its thermal stability by additions of Al2O3 or by doping with CeO2, or La2O3. However, contrary to expectations based on some information in the literature, we have found that the activity decreased in the sequence of Al2O3 > ZrO2 > TiO2, and was not a direct function of specific surface area. This was especially evident in the case of titania. The surface structure of the support and the nature of its interaction with the active component PdO seem to play a far more important role in activity than the apparent specific surface area. Moreover, anatase‐supported catalysts present a very rapid deactivation, whereas rutile‐supported catalysts are relatively stable. The observed phenomena could potentially be related to the interaction between support and the active phase of palladium. Several models have been proposed to describe the strong metal‐support interaction, but either charge transfer or encapsulation seems to be the most probable.

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Section: Introductionmentioning

confidence: 99%

Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

2020

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“…A heterogeneous one-dimensional unstationary model taking plug flow assumption is used. Such a model is considered to be a good balance between accuracy and complexity ,, and is chosen in this work for such reason. An unstationary model can give out the evolution of temperature and reactant concentration distribution under unsteady state conditions, which meets the requirements of this work.…”

Section: Mathematical Modelingmentioning

confidence: 99%

“…Reverse flow reactors (RFRs), a type of forced unsteady state catalytic reactor, have proved to be one of the effective solutions for waste gas decontamination, such as SO 2 oxidation, − decontamination of a diluted VOC gas stream − and the selective reduction of NO x . − A RFR is a catalytic fixed bed reactor, in which the feed flow direction is reversed periodically. When exothermic reactions are conducted in the reactor, a temperature wave is generated that creeps along with the gas flow.…”

Section: Introductionmentioning

confidence: 99%

Resonance Response of Reverse Flow Reactors: A Numerical Simulation

Zhu

Chen

et al. 2015

Ind. Eng. Chem. Res.

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The effect of periodic time-varying inlet parameters on reverse flow reactor behavior is simulated using a onedimensional heterogeneous model with methane as the model reactant. When the flow-reversal cycle is an odd multiple of the inlet concentration variation cycle, a resonance response occurs. Such reactor behavior will occur with various values of superficial inlet velocity, mean inlet methane concentration, flow-reversal time and inert-to-catalyst ratios during this simulation work. A synchronization of the two cycles will cause a sharp increase in the variation of maximum temperature, which may impair reactor stability. Simulation results reveal that the resonance response is attributed to the breakdown of temporal and spatial symmetry in the temperature field of reactor. When a resonance response occurs, adjusting the flow-reversal time is a feasible method to maintain autothermal operation of the reactor. Different from commonly used control strategies both increasing and decreasing flow-reversal time can be used to avoid reactor extinction, and so does avoiding thermal runaway. Simulation work of introducing periodic variation of inlet gas velocity is performed, and a similar resonance response behavior is observed. INTRODUCTIONReverse flow reactors (RFRs), a type of forced unsteady state catalytic reactor, have proved to be one of the effective solutions for waste gas decontamination, such as SO 2 oxidation, 1−3 decontamination of a diluted VOC gas stream 4−7 and the selective reduction of NO x . 8−10 A RFR is a catalytic fixed bed reactor, in which the feed flow direction is reversed periodically. When exothermic reactions are conducted in the reactor, a temperature wave is generated that creeps along with the gas flow. The catalyst at either end acts as a heat regenerator, while the released heat is trapped in the reactor, which maintains the temperature plateau within the reactor and sustains the catalytic reaction even with weak exothermic effects. So, the catalyst packing at the two ends is normally substituted by inert materials for economic reasons.A determination of the steady states of such a system and the construction of a corresponding control strategies are of primary interest in chemical engineering because only steady state or pseudosteady state (PSS) operation has a realistic meaning. However, the RFR behaves in a rather sophisticated manner because of its inherent nonstationary character derived from forced unsteady operation. A number of efforts have been made to establish the dependence of reactor performance on many design and operating parameters, such as reactor length, gas flow rate, flow-reversal time, inlet concentration, wall effects and reaction kinetics. A number of mathematical models and simulation methods have been developed for the dynamic calculation of PSS and the sensitivity analysis over an extended range of parameters. Detailed reviews were provided by Matros 11 and Kolios. 12 A comprehensive survey on RFR performance and model simplification was given by Marín. 4,...

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“…Currently, it accounts for the major contribution to CH 4 release in optimized aftertreatment systems since the stable nature of the CH 4 molecule (C–H bond energy = 439 kJ/mol) hinders its low temperature abatement . Several approaches have been considered to reduce its ignition delay, including innovative design of the reactor setup for faster heating and optimization of the Pd active phase for CH 4 activation at lower temperature. , This is often accomplished by tuning the optimal amount of Pd x + surface species (0 ≤ x ≤ 4) which are stabilized on the surface and subsurface region based on reaction conditions, surface dopants, and support type. − …”

Section: Introductionmentioning

confidence: 99%

Pd/CeO₂ Catalysts Prepared by Solvent-free Mechanochemical Route for Methane Abatement in Natural Gas Fueled Vehicles

Danielis

Colussi

Llorca

et al. 2021

Ind. Eng. Chem. Res.

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The increasing diffusion of alternative mobility solutions, ranging from electric technologies to natural gas fueled vehicles (NGVs), has led to a progressive life-cycle analysis approach of their environmental impact in terms of greenhouse gases (GHGs) emissions. This new approach prompted a careful design of the NGVs catalytic aftertreatment system in order to minimize the catalytic converter carbon footprint as well as the unburned methane emissions at tailpipe. Here, a series of Pd/CeO2 methane oxidation catalysts were prepared by an environmentally friendly solvent-free method and compared to the commercial wet-synthesized state-of-the-art catalysts. Their application in NGVs aftertreatment systems was evaluated by testing powder catalysts and coated monolith cores for CH4 oxidation and steam reforming, which are the main methane abatement reactions occurring in a three-way catalyst (TWC) under lean and rich conditions, respectively. Pd/CeO2 catalysts prepared by mechanochemical synthesis initially displayed superior activity compared to their counterpart obtained by conventional wet impregnation, especially under lean oxidation conditions, but appeared less resistant to the industrial aging process after core washcoating. Lambda sweep experiments carried out under full gas composition proved that, despite needing further optimization in the washcoating and aging processes, the developed mild milling synthesis procedure is a viable way for the production of Pd/CeO2 based catalysts for natural gas TWCs.

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Modeling of Autocyclic Reactor for the Removal of Unburned Methane from Emissions of Natural Gas Engines

Cited by 6 publications

References 22 publications

Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

Resonance Response of Reverse Flow Reactors: A Numerical Simulation

Pd/CeO₂ Catalysts Prepared by Solvent-free Mechanochemical Route for Methane Abatement in Natural Gas Fueled Vehicles

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Modeling of Autocyclic Reactor for the Removal of Unburned Methane from Emissions of Natural Gas Engines

Cited by 6 publications

References 22 publications

Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

Resonance Response of Reverse Flow Reactors: A Numerical Simulation

Pd/CeO2 Catalysts Prepared by Solvent-free Mechanochemical Route for Methane Abatement in Natural Gas Fueled Vehicles

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Pd/CeO₂ Catalysts Prepared by Solvent-free Mechanochemical Route for Methane Abatement in Natural Gas Fueled Vehicles