Membrane reactors, methane partial oxidation

Fig. 4. Configuration of a ceramic membrane reactor for partial oxidation of methane. The membrane tube, with an outside diameter of about 6.5 mm and a length of up to about 30 cm and a wall thickness of 0.25-1.20 mm, was prepared from an electronic/ionic conductor powder (Sr-Fe-Co-O) by a plastic extrusion technique. The quartz reactor supports the ceramic membrane tube through hot Pyrex seals. A Rh-containing reforming catalyst was located adjacent to the tube (57).

Fig. 6. Configuration of a ceramic membrane reactor for partial oxidation of methane. The membrane disk was prepared by pressing Bao.5Sro.5Coo.8Feo.2O3-s oxide powder in a stainless steel module (17 mm inside diameter) under a pressure of (1.3-1.9) X 109 Pa. The effective area of the membrane disk exposed to the feed gas (CH4) was 1.0 cm2 (72).

The viability of one particular use of a membrane reactor for partial oxidation reactions has been studied through mathematical modeling. The partial oxidation of methane has been used as a model selective oxidation reaction, where the intermediate product is much more reactive than the reactant. Kinetic data for V205/Si02 catalysts for methane partial oxidation are available in the literature and have been used in the modeling. Values have been selected for the other key parameters which appear in the dimensionless form of the reactor design equations based upon the physical properties of commercially available membrane materials. This parametric study has identified which parameters are most important, and what the values of these parameters must be to realize a performance enhancement over a plug-flow reactor. 

S. Pei, M.S. Kleefisch, T.P. Kobylinski, K. Faber, C.A. Udovich, V. Zhang-McCoy, B. Dabrowski, U. Balachandran, R.L. Mieville and R.B. Poeppel, Failure mechanisms of ceramic membrane reactors in partial oxidation of methane to synthesis gas. Catal. Lett., 30 (1995) 210-212. 

Jin, W., Gu, X., Li, S. et al. (2000) Experimental and simulation study on a catalyst packed tubular dense membrane reactor for partial oxidation of methane to syngas. Chemical Engineering and Science, 55 (14), 2617-2625. 

Ikeguchi M,MimiuaT, Sekine Y, Kikuchi E and Matsukata M (2005), Reaction and oxygen permeation studies in Smo,4Bao.6Coo,2Feo,803.5 membrane reactor for partial oxidation of methane to syngas, Appl CatalA-Gen, 290,212-220. 

Jin W, Li S, Huang P, Xu N, Shi J and Lin Y S (2000), Tubular lanthanum cobaltite perovskite-type membrane reactors for partial oxidation of methane to syngas , / Membrane Sci, 166,13-22. 

Zhang Y, Liu J, Ding W and Lu X (2011), Performance of an oxygen-permeable membrane reactor for partial oxidation of methane in coke oven gas to syngas , fwe/, 90,324-330. 

Figure 14.16 Scheme of the electrochemical membrane reactor for partial oxidation of methane [119]. 

Basile, A. and Paturzo, L. (2001). An Experimental Study of Multilayered Composite Palladium Membrane Reactors for Partial Oxidation of Methane to Syngas, Catal Today, 67, pp. 55-64. 

Tsai, C., Dixon, A., Moser, W., et al. (1997). Dense Perovskite Membrane Reactors for Partial Oxidation of Methane to Syngas, AICHE J., 43, pp. 2741-2750. 

Jin, W, Li, S., Huang, R, etal. (2000). TnbnlarLanthanumCobaltite Perovskite-Type Membrane Reactors for Partial Oxidation of Methane to Syngas, J. Membrane Set, 166, pp. 13-22. Sammells, A., Schwartz, M., Mackay, R., etal. (2000). Catalytic Membrane Reactors for Spontaneous Synthesis Gas Production, Catal. Today, 56, pp. 325-328. 

Ikeguchi, M., Mimura, T., Sekine, Y., etal. (2005). Reaction and Oxygen Permeation Studies in Smo.4Ba o.6P 0.8Coo.203 5 Membrane Reactor for Partial Oxidation of Methane to Syngas, Appl. Catal. A Gen., 290, pp. 212-220. 

Yin, X., Hong, L. and Liu, Z. (2007). Asymmetric Tubular Oxygen-Permeable Ceramic Membrane Reactor for Partial Oxidation of Methane, J. Phys. Chem. C, 111, pp. 9194-9202. 

Zhang, Y, Liu, J., Ding, W., et al. (2011). Performance of an Oxygen-Permeable Membrane Reactor for Partial Oxidation of Methane in Coke Oven Gas to Syngas, Fuel, 90, pp. 324-330. 

Yang, C., Xu, N.R and Shi, J. (1998) Experimental and modeling study on a packed-bed membrane reactor for partial oxidation of methane to formaldehyde. Industrial Engineering Chemistry Research, 37, 2601-2610. 

Fig. 7. Methane conversion, CO selectivity, and oxygen flux through the ceramic membrane during the partial oxidation of methane in a ceramic membrane reactor (see Fig. 6). Reaction conditions temperature, 1148 K catalyst, 300 mg of LiLaNi0JC/y-Al203 air flow rate, 300 mL min-1 (NTP) feed gas molar ratio, CH4/He = 1/1 feed flow rate, 42.8 mL min-1 (NTP) (72).

It is expected that the conclusions reached in the analysis of the series reaction will also be valid for methane partial oxidation. The first objective of this study was to verify this expectation. The second objective of the study was to determine how much faster than methane formaldehyde must permeate for the membrane reactor to begin to outperform a plug-flow reactor. 

C.-Y. Tsai, Y.H. Ma, W.R. Moser and A.G. Dixon, Simulation of nonisothermal catalytic membrane reactor for methane partial oxidation to syngas, in Y.H. Ma (Ed.), Proceedings of the 3rd International Conference on Inorganic Membranes, Worcester, 1994, pp. 271-280. 

Caro J, Schiestel T, et al., Perovskite hoUow-fiber membranes in the partial oxidation of methane to synthesis gas in a membrane reactor, Desalination 2006 129 415-417. 

The objective of this study was to determine the conversion and selectivity of the methane partial oxidation reaction when using high feed rates and low methane/oxygen feed ratios in the membrane reactor configuration. 

A Rh supported catalyst was chosen because Rh has been shown to be one of the most active and selective catalysts for methane partial oxidation [6-8]. A 3% Rh/Ti02 was the most active catalyst, which ignited at 320°C in a fixed bed microreactor when using methane and oxygen feed rates of 500 and 250 cc/min respectively. It yielded a methane conversion of 70% and a CO selectivity of 85%[10]. It was also found that 100% oxygen conversion is achieved in all cases and that the ignition temperature could be even lower for lower methane/oxygen feed ratios. Experiments were performed initially in the fixed bed reactor so that results obtained in the membrane reactor could be compared to those obtained in the fixed bed reactor. 

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