Comprehensive model of oxidative coupling of methane in a fluidized-bed reactor

Pannek, U.; Mleczko, Lesław

doi:10.1016/0009-2509(96)00401-0

Cited by 26 publications

(23 citation statements)

References 23 publications

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“…The high conversion in the bubble formation zone that is characterized by intensive interphase gas exchange and plug-flow of gas reduces the influence of gas backmixing in the emulsion phase and the mass transport limitation between the bubbles and the emulsion phase. For the same reasons the effect of homogeneous gas phase reactions that take place mainly in the bubbles can mostly be neglected for laboratory-scale fluidized beds (Do et al, 1995;Pannek and Mleczko, 1996). The results obtained in this study qualitatively agree with the results of Do et al (1995), who measured lower C2+ selectivities and yields in a spouted bed and in a spouted bed with a draft tube than in the fluidized bed.…”

Section: Factors Influencing C2 Selectivity and Yield In Various Reacsupporting

confidence: 87%

“…E-mail address: L.Mleczko@risc.techem.ruhr-uni-bochurn.de of methane in fluidized-bed reactors, Cz+ selectivity was influenced by mass transport limitation between bubbles and the emulsion as well as by the backmixing of gas in the emulsion. At high temperatures and partial pressures of oxygen, the mass transport restrictions and backmixing of gas suppressed high selectivity and yield to higher hydrocarbons (Pannek and Mleczko. 1996).…”

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Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Mleczko

Marschall

1997

Can J Chem Eng

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The oxidative coupling of methane to C2-hydrocarbons (OCM) over a La2031Ca0 catalyst (27 at.%) was investigated in an internally circulating fluidized-bed (ICFB) reactor (IDe,).= 1.9 cm, H,.isl,r = 20.5 cm). The experiments were performed in the following range of conditions: T = 8O0-90O0C, pcH4:po2:pN2 = 57.144: 1&22.9:20 kPa. The obtained C, selectivities and C, yields were compared with the corresponding data from a spouted-fluid-bed reactor (ID = 5 cm) and a bubbling fluidized-bed (FIB) reactor (ID = 5 cm). The maximum C, yield in the internally circulating fluidized-bed (ICFB) reactor amounted to 12.2% ( T = 860"C, 38.7% C, selectivity, 3 1.5% methane conversion), whereas in the FIB reactor a maximum C2 yield of 13.8% ( T = 840°C, 40.4% C, selectivity, 34.2% methane conversion) was obtained. The lowest Cz yield was achieved in the spouted-bed (SFB) reactor (&? = 1 1.6%, T = 84OoC, 36.2% C, selectivity, 32.0% methane conversion). The highest space-time yield of 24.0 mol/kg,,;h was obtained in the ICFB reactor, whereas in a FIB reactor only a space-time yield of 9.6 mol/kg,,,~h could be obtained. Keywords: internally circulating fluidized-bed reactor, oxidative coupling, methane.xidative coupling of methane (OCM) to higher hydro-0 carbons is a possible route to convert natural gas into chemical or petrochemical feedstocks. However, further improvement of the catalytic performance by developing more selective catalysts and also by reaction engineering methods is necessary to make this process commercially viable (Mleczko and Baerns, 1995). The main engineering challenge is given by the temperature control and the management of the large amounts of heat generated in the reaction. From this point of view, a fluidized bed seems to be the most suitable reactor type to perform this reaction in a controlled manner. In laboratory-scale fluidized beds for several catalysts, e.g. a La2031Ca0 catalyst (Mleczko et al., 1996a), a LilSnlMgO catalyst (Santos et al., 1995) or a (Sro 125Mgo.,,5)C03 catalyst (Do et al., 1994), C2+ yields above 15% or even slightly higher have been reported. C2+ selectivities and yields obtained in fluidized-bed reactors were comparable and under certain conditions even better than in fixed beds (Follmer et al., 1988;Do et al., 1995;Mleczko et al., 1996a). However, lower selectivities and yields have also been reported (e.g. Mleczko et al., 1996b).In order to explain these contradictory results, the complex interaction between the bed hydrodynamics and kinetics of chemical reactions on the product distribution has to be taken into account, i.e. when performing oxidative coupling *Author to whom correspondence should be addressed. E-mail address: L.Mleczko@risc.techem.ruhr-uni-bochurn.de of methane in fluidized-bed reactors, Cz+ selectivity was influenced by mass transport limitation between bubbles and the emulsion as well as by the backmixing of gas in the emulsion. At high temperatures and partial pressures of oxygen, the mass transport restrictions and backmixing of gas suppressed high s...

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Section: Factors Influencing C2 Selectivity and Yield In Various Reacsupporting

confidence: 87%

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Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Mleczko

Marschall

1997

Can J Chem Eng

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“…1 cm (Yates, 1983) it can be expected that oxygen conversion is only influenced to a small extent by the mass transport between bubbles and the emulsion phase. This conclusion is supported by simulation results (Mleczko et al, 1992;Pannek and Mleczko, 1996) in which small differences between the oxygen concentration in bubbles and in the emulsion phase were predicted for a laboratory-scale reactor.…”

Section: Pathway Of Ocm In a Fluidized-bedsupporting

confidence: 58%

Oxidative coupling of methane over a La₂O₃/CaO catalyst. Optimization of reaction conditions in a bubbling fluidized‐bed reactor

et al. 1996

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Oxidative coupling of methane over a La2O3/CaO catalyst was investigated in laboratory‐scale fluidized‐bed reactors (ID = 5 and 7 cm) in the following range of reaction conditions: T = 700 – 880°C, P CH 4 = 41 – 72 kPa and P O 2 = 6 – 29 kPa. The maximum C2+ selectivity and yield amounted to 73.8% (T = 800°C, X CH 4 = 13.1%, Y C 2+ = 9.7%) and 16.0% (T = 840°C, X CH 4 = 34.0%, S C 2+ = 47.2%), respectively. Axial gas concentration profiles revealed that C2+ selectivity was not only influenced by oxidative consecutive reactions, but also by steam reforming of ethylene. When diluting the catalytic bed (mcat = 145 g) with quartz (m siO 2 = 200 and 400 g), a slight decrease of the selectivity (1–2%) was observed. The dilution of the feed gas with nitrogen only led to only a small increase (< 2%) of the C2+ selectivity.

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“…reported C 2 yields of 15.5% together with 31% methane conversion and 51% C 2 selectivity, which were too far from commercial application limits . Pannek and Mleczko modeled and simulated OCM in a fluidized‐bed reactor, and observed C 2 yields up to 17% which is slightly higher than those obtained in packed‐beds. The same authors also concluded that, in an industrial fluidized‐bed reactor, C 2 yields will be lower when compared with a lab‐scale reactor, due to larger contact times .…”

Section: Introductionmentioning

confidence: 99%

“…Control of temperature, residence time and its distribution depends strongly on the structure and geometry of the catalytic reactor. Even though many studies have been carried out for formulating catalysts to achieve high methane conversion together with improved product selectivity and ethylene yield, the number of studies addressing the effect of reactor type and structure is scarce . The very first reactors used to test OCM were packed‐bed type, which led to the formation of axial and radial temperature gradients in the reactor due to the high exothermicity .…”

Section: Introductionmentioning

confidence: 99%

Parametric investigation of oxidative coupling of methane in a heat‐exchange integrated microchannel reactor

Tezcan

Avcı

2014

J of Chemical Tech & Biotech

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BACKGROUND Oxidative coupling of methane (OCM) to C2 hydrocarbons is strongly exothermic and requires careful management of the dissipated heat. Running OCM in microchannel reactors offers fast heat transfer rates that enable controlled distribution of reaction temperature and product composition. This study involves modeling and simulation of OCM in a heat exchange integrated microchannel reactor involving parallel reaction and cooling channels separated by solid walls. RESULTS Using separating wall with high thermal conductivity and thickness above 5 × 10‐4 m regulates temperature distribution along the reaction channel and improves C2 yield. Increasing the methane‐to‐oxygen ratio decreases the reaction temperature and conversion immediately. Coolant inlet temperature affects the trade‐off between methane conversion and selective production of ethane and ethylene. Exothermic heat release and C2 hydrocarbon loss by oxidation are pronounced at higher reactant mass flow rates, whereas C2 yield is improved at higher coolant mass flow rates that dampen the reaction temperature. CONCLUSION Effective heat transfer and improved temperature control can be obtained in the microchannel geometry. The results provide insight into the potential use of microreactors, novel units known to have robust heat transfer properties, in controlling the temperature of the OCM process, which is one of the key design targets affecting product selectivity. © 2014 Society of Chemical Industry

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Comprehensive model of oxidative coupling of methane in a fluidized-bed reactor

Cited by 26 publications

References 23 publications

Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Oxidative coupling of methane over a La₂O₃/CaO catalyst. Optimization of reaction conditions in a bubbling fluidized‐bed reactor

Parametric investigation of oxidative coupling of methane in a heat‐exchange integrated microchannel reactor

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Comprehensive model of oxidative coupling of methane in a fluidized-bed reactor

Cited by 26 publications

References 23 publications

Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Oxidative coupling of methane over a La2O3/CaO catalyst. Optimization of reaction conditions in a bubbling fluidized‐bed reactor

Parametric investigation of oxidative coupling of methane in a heat‐exchange integrated microchannel reactor

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Oxidative coupling of methane over a La₂O₃/CaO catalyst. Optimization of reaction conditions in a bubbling fluidized‐bed reactor