Kinetic studies of the oxidative coupling of methane over a NaOH/CaO catalyst

Lehmann, L.; Baerns, M.

doi:10.1016/0021-9517(92)90048-m

Cited by 42 publications

(7 citation statements)

References 25 publications

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“…For the kinetic model homogeneous gas phase reactions had to be taken into account, however. The negative effect of the oxygen partial pressure on selectivity is to be ascribed to the different kinetic orders in oxygen for the selective and non-selective steps as found by Lehmann and Baerns (1990). The order for the selective route was lower compared to the non-selective step.…”

Section: C2+ Selectivitymentioning

confidence: 88%

“…For all catalysts C2+ selectivity increases with increasing methane partial pressure and decreasing oxygen partial pressure. The increase of C2+ selectivity with increasing temperature in the lower temperature range may be due to the higher activation energy of the selective reaction step to C2 hydrocarbons compared to the non-selective step to COX (Lehmann and Baerns, 1990). The decrease in selectivity within the high temperature regime can be explained by an enhanced total oxidation of the C2 products formed, occurring mostly in the gas phase.…”

Section: C2+ Selectivitymentioning

confidence: 99%

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Oxidative coupling of methane in a bubbling fluidized bed reactor

et al. 1991

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The oxidative coupling of methane to higher hydrocarbons (C2+) was studied in a bubbling fluidized bed reactor between 700°C and 820°C, and with partial pressures of methane from 40 to 70 kPa and of oxygen from 2 to 20 kPa; the total pressure was ca 100 kPa. CaO, Na2CO3/CaO and PbO/γ‐Al2O3 were used as catalytic materials. C2+ selectivity depends markedly on temperature and oxygen partial pressure. The optimum temperature for maximizing C2+ selectivity varies between 720 and 800°C depending on the catalyst. Maximum C2+ selectivities were achieved at low oxygen and high methane partial pressures and amounted to 46% for CaO (T = 780°C; PCH4 = 70 kPa; PO2 = 5 kPa), 53% for Na2CO3/CaO (T = 760°C; PCH4 = 60 kPa; PO2 = 6 kPa) and 70% for PbO/γ‐Al2O3 (T = 720°C; PCH4 = 60 kPa; PO2 = 5 kPa). Maximum yields were obtained at low methane‐to‐oxygen ratios; they amounted to 4.5% for CaO (T = 800°C; PCH4 = 70 kPa; PO2 = 12 kPa), 8.8% for Na2CO3/CaO (T = 820°C; PCH4 = 60 kPa; PO2 = 20 kPa) and 11.3% for PbO/γ‐Al2O3 (T 2= 800°C; PCH4 = 60 kPa; PO2 = 20 kPa).

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Section: C2+ Selectivitymentioning

confidence: 88%

Section: C2+ Selectivitymentioning

confidence: 99%

Oxidative coupling of methane in a bubbling fluidized bed reactor

et al. 1991

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“…Rate equations for methane oxidative coupling, based on the mechanistic proposals of previous investigators (Korf et al, 1987(Korf et al, ,1990Tong et al, 1990; Lehmann and Baerns, 1992; Shimada and Galuszka, 1992) and the assumption that CO2 deactivates peroxide catalytic sites via carbonate formation, have been derived. The modified models are able to describe the observed increase in C2 selectivity and decrease in CH4 conversion when CO2 is added to the feed gas of a Li/Pb/Ca catalyst, in addition to the selectivity and conversion trends measured over a wide range of operating conditions.…”

Section: Discussionmentioning

confidence: 99%

Effect of carbon dioxide on methane oxidative coupling kinetics

Smith¹,

Gałuszka²

1994

Ind. Eng. Chem. Res.

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“…Mechanism and Rate Expressions. Researchers(Lehmann and Baerns, 1992) have reported different reaction rate expressions based on a number of mechanisms to predict the hydrocarbon formation rate and carbon oxide formation rate in terms of Pch4 and P02• None of the earlier studies included the dependence of P2 and Ri on Pco2• Ross and co-workers(Roos et al, 1989) developed expressions for Pch4 as a function of methane, oxygen, and carbon dioxide partial pressures, but separate expressions for R1 and P2 were not reported.…”

mentioning

confidence: 99%

Effects of carbon dioxide during oxidative coupling of methane over lithium/magnesia: mechanisms and models

Al‐Zahrani¹,

Song²,

Lobban³

1994

Ind. Eng. Chem. Res.

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The effects of CO2 partial pressure on oxidative methane coupling over a Li/MgO catalyst were studied under low conversion conditions in a flow reactor. Methane to oxygen ratios from 0.5 to 35 and temperatures from 973 to 1073 K were used in the experiments and modeling. Varying flow rates of CO2 were mixed with the methane and oxygen prior to the reaction. Results indicate that CO2 has a poisoning effect on both carbon oxides (CO and CO2) and C2 hydrocarbon (C2H4 and C2H6) formation rates, while selectivity to the C2 hydrocarbon was not significantly affected. The apparent activation energy increased with CO2 partial pressure in the feed. Results also indicate that a small amount of methane reacts with carbon dioxide to produce carbon monoxide. Empirical rate expressions and rate expressions rigorously derived from proposed mechanisms were obtained. The rate expressions agree well with the measured rates and also predict the observed trend in apparent activation energy.

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Kinetic studies of the oxidative coupling of methane over a NaOH/CaO catalyst

Cited by 42 publications

References 25 publications

Oxidative coupling of methane in a bubbling fluidized bed reactor

Oxidative coupling of methane in a bubbling fluidized bed reactor

Effect of carbon dioxide on methane oxidative coupling kinetics

Effects of carbon dioxide during oxidative coupling of methane over lithium/magnesia: mechanisms and models

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