Oxidative coupling of methane over

S. Seimanides, P. Tsiakaras, X.E. Verykios, and C.G. Vayenas, Oxidative Coupling of Methane over Yttria-doped Zirconia Solid Electrolyte, Appl. Catal. 68, 41-53 (1991). 

Oxidative Coupling of Methane over Praseodymium Oxide in the Presence and Absence of Tetrachloromethane... 

Conversion and C2+ selectivity for oxidative coupling of methane over praseodymium oxide in the presence and absence of TCM. 

Oxidative Coupling of Methane over Alkali-Promoted Simple Molybdate Catalysts... 

Redox Cycle During Oxidative Coupling of Methane over PbO—MgO—AI2O3 Catalyst... 

Figures Proposed reaction mechanism for the oxidative coupling of methane over nonreducible oxide catalysts. Thicker line indicates a main pathway, thinner line corresponds to a minor pathway.

A general mechanism of the oxidative coupling of methane over reducible oxide catalysts has been proposed by Lee and Oyama. Their reaction sequence is based on the cracking mechanism suggested by Kolts and Delzer which was adapted to the methane dimerization process. The similarities between these two processes as indicated by Lee and Oyama were as follows (1) the same materials (Mn/MgO, Fe/MgO, LajOj, Ce02) are active in both reactions,... 

Other steps used in the model assume that the heterogeneous conversion of methane is limited to the gas-phase availability of oxygen, O2 adsorption is fast relative to the rate of methane conversion, and heat and mass transports are fast relative to the reaction rates. Calculations for the above model were conducted for a batch reactor using some kinetic parameters available for the oxidative coupling of methane over sodium-promoted CaO. The results of the computer simulation performed for methane dimerization at 800 °C can be found in Figure 7. It is seen that the major products of the reaction are ethane, ethylene, and CO. The formation of methanol and formaldehyde decreases as the contact time increases. 

THE EFFECTS OF GAS COMPOSITION AND PROCESS CONDITIONS ON THE OXIDATIVE COUPLING OF METHANE OVER Li/MgO CATALYST... 

Ross and co-workers [9,10] have explored the influence of CO2 on the oxidative coupling of methane over the Li/MgO catalyst. They found that carbon dioxide in the gas phase lowers both the methane conversion and the yield of ethane/ethylene products. They also found that carbon dioxide significantly improves the stability of the catalyst against deactivation. Based on the observations of surface species from FTIRS and transient experiments. In addition, most of the observations and experimental results reported to date cover a limited range of methane to oxygen feed ratios. There is a need to study the reaction over a wide range of methane to oxygen ratios and to quantify the effects of carbon dioxide on the reaction rates. 

The Effect of the PbO Loading in the Oxidative Coupling of Methane over PbO/Si02 Catalysts. 

Table 1 shows the catalytic properties for the oxidative coupling of methane over 2, 6 and 10 % PbO/Si02 catalysts at different CH4/O2 ratios at 1048 K, using 250 mg of catalyst. It was also run using 500 mg of 10 % PbO/Si02 catalyst at a CH4/O2 = 2 ratio. As it is well known on OCM catalysts, the CH4 conversion decreases and the C2 selectivity increases when the CH4/O2 ratio increases. For the 2 and 6 % PbO/Si02 catalysts. 

OXIDATIVE COUPLING OF METHANE OVER PROMOTED MAGNESIUM OXIDE CATALYSTS RELATION BETWEEN ACTIVITY AND SPECIFIC SURFACE AREA... 

Oxidative coupling of methane over alkaline earth promoted Ce02, Nd203 and Sm203 catalysts... 

Ghoudary, V. R., Mulla, S. A. R., and Uphade, B. S. 1997. Oxidative coupling of methane over supported LajOj and La-promoted MgO catalysts influence of catalyst-support interactions. Ind. Eng. Chem. Res. 36 2096-2100. 

Table IIL5. Oxidative coupling of methane over various heterogeneous metal oxide catalysts.

Peil KP, Marcelin G, Goodwin JG, Jr, Kiennemann A, Transient kinetic analysis of the oxidative coupling of methane over Sm203, in Albright LF (ed.), Novel Production Methods for Ethylene, Light Hydrocarbons and Aromatics, Marcel Dekker Inc. New York, pp. 61-74, 1992. 

In the present study, the influence of the catalyst particle size on the methanol oxidation and the oxidative coupling of methane over copper has been investigated between 350°C and 900°C. TPR/TPO and TG/DTA was used for the determination of the redox behaviour and SEM for the morphological characterization at the different stages of the reaction. 

Comprehensive kinetics of oxidative coupling of methane over the La203/Ca0 catalyst. Ind. Eng. Chem, Res.,... 

Wang, D., Rosynek, M. and Lunsford, J. (1995). Oxidative Coupling of Methane over Oxide-Supported Sodium-Manganese Catalysts, J. Catal, 155, pp. 390-402. 

Choudhary VR, Mulla SAR, Uphade BS (1999) Oxidative coupling of methane over alkaline earth oxides deposited on commercial support precoated with rare earth oxides. Fuel 78 427 37... 

Pak S, Lunsford JH (1998) Thermal effects during the oxidative coupling of methane over Mn/Na2W04/Si02 and Mn/Na2W04/Mg0 catalysts. Appl Catal Gen 168 131-137... 

Wang D, Rosynek MP, Lunsford JH (1995) Oxidative coupling of methane over oxide-supported sodium-manganese catalysts. J Catal 155 390 02... 

Xu Y, Yu L, Guo X (1997) Effect of basicity and adding CO2 in the feed on the oxidative coupling of methane over K2O and SrO promoted La203/Zn0 catalysts. Appl Catal Gen 164 47-57... 

Aika K, Nishiyama T (1988) Utilisation of CO2 in the oxidative coupling of methane over PbO-MgO and PbO-CaO. J Chem Soc Chem Commun 1 70-71... 

Choudhary, V.R., Uphade, B.S., and MuUa, S.A.R. Oxidative coupling of methane over a Sr-promoted La203 catalyst supported on a low surface area porous catalyst carrier. Ind Eng. Ghent. Res. 1997, 36, 3594-3601. 

Lacombe, S., Geantet, C., and Mirodatos, C. Oxidative coupling of methane over lanthana catalysts. 1. Identification and role of specific active sites../ Catal 1995, 151, 439 52. 

Buyevskaya, O.V., Rothaemel, M., Zanthoff, H.W., and Baems, M. Transient studies on reaction steps in the oxidative coupling of methane over catalytic surfaces of MgO and Sm203.J. Catal. 1994,146, 346-257. 

Dissanayake, D., Lunsford, J.H., and Rosynek, M.R Oxidative coupling of methane over oxide-supported barium catalysts. J. Catal. 1993, 143, 286-298. 

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