Model methane oxidative coupling

Godini, H., Arellano-Garcia, H.,Omidkhah, M., etal. (2010). Model-Based Analysis of Reactor Feeding Policies for Methane Oxidative Coupling, Ind. Eng. Chem. Res., 49, pp. 3544-3552. Tullo, A. (2011). Ethylene from Methane, Chem. Eng. News, 89, pp. 20-21. 

Vatani A, Jabbari E, Askarieh M, Torangi MA. Kinetic modeling of oxidative coupling of methane over Li/MgO catalyst by genetic algorithm. J Nat Gas Sci Eng. 2014 20 347-56. 

Methane can be oxidatively coupled to ethylene with very high yield using the novel gas recycle electrocatalytic or catalytic reactor separator. The ethylene yield is up to 85% for batch operation and up to 50% for continuous flow operation. These promising results, which stem from the novel reactor design and from the adsorptive properties of the molecular sieve material, can be rationalized in terms of a simple macroscopic kinetic model. Such simplified models may be useful for scale up purposes. For practical applications it would be desirable to reduce the recycle ratio p to lower values (e.g. 5-8). This requires a single-pass C2 yield of the order of 15-20%. The Sr-doped La203... 

Devol, A.H., Anderson, J.J., Kuivila, K., and Murray, J.W. (1984) A model for coupled sulfate reduction and methane oxidation in the sediments of Saanich Inlet. Geochim. Cosmochim. Acta 48, 993-1004. 

While Eqn. (1) predicts OH levels in the remote troposphere in reasonably good agreement with the predictions of more elaborate photochemical models which properly treat the HO2/OH coupling, for conditions appropriate for less remote regions where enhanced NOx levels are commonly encountered Eqn. (1) does not accurately calculate the OH concentrations. This is because as NOx levels increase, a greater fraction of the HO2 radicals produced from the methane oxidation reaction sequence react with NO via (R8) to regenerate OH. Thus as illustrated in Figure 4, the levels of OH calculated in a complete photochemical model increase substantially as NOx levels increase from the pptv level (typical of remote marine conditions) to the more polluted ppbv level. For NOx levels in... 

Kinetic modeling. - The discussion xesented so far clearly shows that the oxidative coupling of methane is a complex process involving homogeneous and heterogeneous 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. 

Y. Lu, A. Ramachandra, Y.H. Ma, W.R. Moser and A.G. Dixon, Reactor modeling of the oxidative coupling of methane in membrane reactors. Paper presented at the 3rd International Congress on Inorganic Membranes, July 10-14,1994, Worcester, MA, USA. 

The coincidence of maxima in the methane oxidation rate and the sulfate reduction rate in Saanich Inlet strongly suggests that the methane oxidizing agent was sulfate, either via direct reaction, or coupled indirectly through reactions with other substrates (Devol, 1983). A methane-sulfate coupled reaction diffusion model was developed to describe the inverse relationship commonly observed between methane and sulfate concentrations in the pore waters of anoxic marine sediments. When fit to data from Saanich Inlet (B.C., Canada) and Skan Bay (Alaska), the model not only reproduces the observed methane and sulfate pore water concentration profiles but also accurately predicts the methane oxidation and sulfate reduction rates. In Saanich Inlet sediments, from 23 to 40% of the downward sulfate flux is consumed in methane oxidation while in Skan Bay this value is only about 12%. 

As discussed above, LES/FMDF can be implemented with (1) nonequilibrium and (2) near-equilibrium combustion models. The former uses a direct ODF solver for the chemistry and can handle finite-rate chemistry effects. In the latter, a flamelet library is coupled with the LFS/FMDF solver in which transport of the mixture fraction is considered. The latter approach has the advantage it is computationally much less intensive and can be conducted with very complex chemical kinetics models. Below, some of the results recently obtained via Fq. (4.2) are presented. The flamelet library is generated with the full methane oxidation mechanism of the Gas Research Institute (GRI) [6] accounting for 53 species and about 300 elementary reactions. 

The activity of the catalysts samples having a cylindrical monolithic substrate were determined only in the model reaction test of methane oxidation, performed in a laboratory test unit coupled with gas cromatografs, equipped with a special reactor for testing monolithic samples. 

Kinetic-Transport Models of Bimodal Reaction Sequences. 1. Homogeneous and Heterogeneous Pathways in Oxidative Coupling of Methane. Chemical Engineering Science, 48(14) 2643-2661. 

Tjatjopoulos, G. J., Ketekides, P. T., latrides, K. K., and Vasolos, I. A., Cold Flow Model and Computer Simulation Studies of a Circulating Fluidized Bed Reactor for the Oxidative Coupling of Methane , Catalysis Today, 21, 387 (1994). 

Copper-based catalysts are of considerable importance for industrial reactions, e. g. partial oxidation reactions. This contribution reports on a broad study of the catalytic activity of copper in model redox reactions, e. g. methanol oxidation and oxidative coupling of methane. In addition the interaction of Cu with these reactive gases was investigated by thermoanalytic techniques (TG/DTA, DSC), temperature programmed oxidation and reduction (TPO/tpR) and thermal desorption spectroscopy (TDS). Scanning electron microscopy (SEM) and electron backscattering diffraction (EBSD) was additionally used to characterise the copper catalyst before and after catalytic action. 

Tye CT, Mohamed AR, Bhatia S. Modeling of catalytic reactor for oxidative coupling of methane using La203/Ca0 catalyst. Chemical Engineering Journal 2002 87 49-59. 

Kimdu, P.K., Zhang, Y, and Ray, A.K. (2009) Modeling and simulation of simulated countercurrent moving bed chromatographic reactor for oxidative coupling of methane. Chem. Eng. Scl,... 

G.B. (2011) Catalyst design based on microkinetic models oxidative coupling of methane. Catal. Today,... 

Figure 5. Reaction scheme for the kinetic models on oxidative methane coupling in the gas phase applied in model A and B.

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