Heterogeneous–homogeneous interactions in catalytic microchannel reactors

Chattopadhyay, Sharmila; Veser, Götz

doi:10.1002/aic.10825

Cited by 39 publications

(29 citation statements)

References 35 publications

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“…microreactors) for high-pressure chemistry. In case of metal-plate based microreactors working pressures are up to 5 bar for gas-phase reactions [11], and up to 150 bar for two-and three-phase reactions [12,13]. For glassbased microreactors working pressures of ∼90 bar are achieved [14].…”

Section: Introductionmentioning

confidence: 99%

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

Tiggelaar¹,

Benito‐Lopez²,

Hermes³

et al. 2007

Chemical Engineering Journal

115

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The design, fabrication and high-pressure performance of several in-plane fiber-based interface geometries to microreactor chips for highpressure chemistry are discussed, and an application is presented. The main investigated design parameters are the geometry of the inlet/outlet structure, the manner in which top and bottom wafer are bonded and the way the inlets/outlets turn over into the microfluidic channels.Destructive pressure experiments with H 2 O and liquid CO 2 showed that the maximum pressure that the proposed inlet/outlet structures can withstand is in the range of 180-690 bar. The optimal geometry for high-pressure microreactor chips is a tubular structure that is etched with hydrofluoric acid (HF) and suitable for fibers with a diameter of 110 m. These inlets/outlets can withstand pressures up to 690 bar. On the other hand, small powderblasted inlets/outlets that are smoothened with HF and with a sharp transition towards the flow channels are adequate for working pressures up to 300 bar.Microreactor chips with tubular inlet/outlet geometries were used for studying the formation of the carbamic acid of N-benzylmethylamine and CO 2 . These chips could be used for pressures up to 400 bar without problems/failure, thereby showing that these micromachined microreactor chips are attractive tools for performing high-pressure chemistry in a fast and safe way.

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Section: Introductionmentioning

confidence: 99%

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

Tiggelaar¹,

Benito‐Lopez²,

Hermes³

et al. 2007

Chemical Engineering Journal

115

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“…While it is impossible "to switch off" homogeneous chemistry in a real combustion system, these computations for this case can give insight into the rate at which the heterogeneous processes take place during combustion, and the products formed by the heterogeneous reactions. More details about this method can be found in previous studies (Chattopadhyay and Veser, 2006;Stefanidis and Vlachos, 2009). The final computing method is for the coupled homogeneousheterogeneous case where both heterogeneous and homogeneous chemistry are allowed to occur within the system.…”

Section: Resultsmentioning

confidence: 99%

“…The basic principles of catalytic combustion have been addressed in past reviews (Pfefferle and Pfefferle, 1987;Prasad et al, 1984). At higher temperatures, there is a significant contribution from homogeneous reactions to the overall reaction-rate in parallel to heterogeneous reactions (Chattopadhyay and Veser, 2006;Stefanidis and Vlachos, 2009). In most cases, the occurrence of homogeneous reactions is an undesired feature, because it complicates the fundamental understanding of reaction mechanisms and results in selectivity losses (Goralski and Schmidt, 1999).…”

Section: Frontiers In Heat and Mass Transfermentioning

confidence: 99%

Combustion and Emissions Characteristics of Methane-Air Mixtures in Catalytic Micro-Combustors: A Computational Fluid Dynamics Study

Chen¹,

Liu²,

Liu³

et al. 2018

Frontiers in Heat and Mass Transfer

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The combustion and emissions characteristics of methane-air mixtures in high-temperature catalytic micro-combustors were studied numerically. Both the heterogeneous and homogeneous chemistry were modeled simultaneously using detailed reaction mechanisms in order to better understand the role of each pathway in determining the product distributions. Computational fluid dynamics simulations were performed at a variety of pressures, temperatures, compositions, and combustor dimensions to determine their effects on the combustion and emissions characteristics. Comparisons were made between the results obtained for a purely heterogeneous case, a purely homogeneous case, and a coupled homogeneousheterogeneous case. It was shown that homogeneous and heterogeneous chemistry take place on similar time-scales with each predicting complete conversion of methane in the system. The contribution of homogeneous and heterogeneous reactions depends strongly upon the operating conditions. The heterogeneous chemistry significantly inhibits the homogeneous chemistry due in part to the radical quenching occurring on the catalytic surfaces, which results in lack of homogeneous chemistry. The inhibiting effect also accounts for the low emissions of nitrogen oxides, as these species are formed by a homogeneous reaction pathway. Nitric oxide is the main nitrogen pollutant formed under lean-burn conditions.

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“…In this situation heat generation is typically faster than heat losses by convection, conduction and radiation leading to high temperatures and interesting phenomena such as coupled surface-gas reactions, mass and heat transport limitations, ignition-extinction of surface chemistry, ignition-extinction of gas phase chemistry and autothermal reactor operation. Of particular interest is the exchange of radicals between the surface and the gas phase [5,6]. As will be outlined in the following scattered experimental and numerical studies exist shedding light onto different aspects of methane oxidation and methane coupling on Pt but it is an open question whether these results can be extrapolated to high temperature (>1000 °C) and high pressure (>10 5 Pa) conditions [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…After gas phase oxygen has been consumed, methane conversion continues with water as co-reactant meaning that steam reforming (Eq. 6) is the dominant reaction path CH 4 + H 2 O → CO + 3H 2 (6) Whereas CO 2 reforming seems to be negligible under high temperature conditions, the water gas shift equilibrium (Eq. 7) might be another important reaction which contributes to the observed product distribution.…”

Section: Introductionmentioning

confidence: 99%

In-situ investigation of gas phase radical chemistry in the catalytic partial oxidation of methane on Pt

et al. 2009

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The catalytic partial oxidation of methane on platinum was studied in situ under atmospheric pressure and temperatures between 1000 and 1300 °C. By combining radical measurements using a molecular beam mass spectrometer and threshold ionization with GC, GC-MS and temperature profile measurements it was demonstrated that a homogeneous reaction pathway is opened at temperatures above 1100 °C, in parallel to heterogeneous reactions which start already at 600 °C. Before ignition of gas phase chemistry, only CO, H 2 , CO 2 and H 2 O are formed at the catalyst surface. Upon ignition of gas chemistry, CH 3 ⋅ radicals, C2 coupling products and traces of C3 and C4 hydrocarbons are observed. Because the formation of CH 3 ⋅ radicals correlates with the formation of C2 products it can be concluded that C2 products are formed by coupling of methyl radicals in the gas phase followed by dehydrogenation reactions. This formation pathway was predicted by numerical simulations and this work presents an experimental confirmation under high temperature atmospheric pressure conditions.

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Heterogeneous–homogeneous interactions in catalytic microchannel reactors

Cited by 39 publications

References 35 publications

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

Combustion and Emissions Characteristics of Methane-Air Mixtures in Catalytic Micro-Combustors: A Computational Fluid Dynamics Study

In-situ investigation of gas phase radical chemistry in the catalytic partial oxidation of methane on Pt

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