Partial oxidation of methane to syngas

The direct catalytic partial oxidation of methane (POM) is a mildly exothermic reaction  

DENSE CERAMIC OXYGEN-PERMEABLE MEMBRANE REACTORS 

In the POM process, the oxide membrane provides only molecular oxygen to react at the catalyst because the lattice oxygen of the membrane is not active in breaking the C-H bond but oxidizes preferentially hydrogen to water [41]. Some of the CO and H2 formed by the reforming reactions is oxidized at the membrane surface into CO2 and H O  

As a result, the oxygen permeation flux under POM reaction conditions is much higher than that when helium is used as sweep gas at the same temperature [42]. Furthermore, the POM catalyst also has a significant influence on the oxygen permeation of the membrane, but the mechanism is not very clear [43]. 

Of all the potential applications of dense ceramic MRs, the POM to syngas is thought to be the most commercially important one. Considerable efforts have been made in this field in the last two decades, as summarized in Table 5.3. 

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The two mechanisms proposed to account for the partial oxidation of methane to syngas may be dedgnated as the IPO (Indirect Partial Oxidation) mechanism and the DPO (Direct Partial Oxidation) mechanism. The IPO mechanism was proposed by Prette et al [16] and Lunsford et al [12]. They think CO and H2 are the products of indirect reaction, the overall reaction of the POM reaction is composed of three different reactions... 

Two conqiletely different behaviors of oxidative transformation of methane, namely the Oxidative Coupling of Methane to C2 Hydrocarbons(OCM) and the Partial Oxidation of Methane to Syngas(POM), were performed and related over the nickel-based catalysts due to different modification and different supports. It is concluded that the acidic property favors keeping the reduced nickel and the reduced nickel is necessary for POM reaction, and the bade property frvors keeping the oxidized nickel and the oxidized mckel is necessary for OCM reaction. POM and OCM reactions proceed at different active sites caused by different... 

Partial oxidation of methane to syngas over Ni and Co catalysts was effected by use of microwave irradiation, and compared with conventional heating [73]. Although the same conversion levels and H2/CO ratio (2.0 0.2) were observed, the temperature of the catalyst bed was much lower (200 K) when microwave irradiation was used than with conventional heating. Under both activation modes the Ni-based... 

Balachandran, U. et al., Dense ceramic membranes for partial oxidation of methane to syngas, Appl. Catal, 133, 19, 1995. 

The synthesis of intermediates and monomers from alkanes by means of oxidative processes, in part replacing alkenes and aromatics as the traditional building blocks for the chemical industry [2]. Besides the well-known oxidation of n-butane to maleic anhydride, examples of processes implemented at the industrial level are (i) the direct oxidation of ethane to acetic acid, developed by Sabic (ii) the ammoxidation of propane to acrylonitrile, developed by INEOS (former BP) and by Mitsubishi, and recently announced by Asahi to soon become commercial (iii) the partial oxidation of methane to syngas (a demonstration unit is being built by ENI). Many other reactions are currently being investigated, for example, (i) the... 

Mayer J, Fichtner M, Wolf D, Schubert K. A microstructured reactor for the catalytic partial oxidation of methane to syngas. Proceedings of the 3rd International Conference on Microreaction Technology. Berlin Springer, 2000 187-196. 

Fichtner, M., Mayer, J., Wolf, D., Schubert, K., Microstructured rhodium catalysts for the partial oxidation of methane to syngas under pressure, Ind. Eng. Chem. Res. 2001, 40, 3475-3483. 

Wang, h., Tablet, C., Schiestel, T., Werth, S. and Caro, J. (2006) Partial oxidation of methane to syngas in perovskite hollow fiber membrane reactor. Catalysis Communications, 7, 907-912. 

Basile, A., Paturzo, L., Lagana, F. (2001). The partial oxidation of methane to syngas in a palladium membrane reactor simulation and experimental studies. Catalysis Today 67,65-75. 

Lyubovsky, M., Roychoudhury, S., and LaPierre, R. Catalytic partial oxidation of methane to syngas at elevated pressures. Catalysis Letters, 2005, 99, 113. 

Burke, N. and David, T. Coke formation during high pressure catalytic partial oxidation of methane to syngas. Reaction Kinetics and Catalysis Letters, 2005, 84, 137. 

Chen, L., Lu, Y., Hong, Q., Lin, J., and Dautzenberg, F.M. Catalytic partial oxidation of methane to syngas over Ca-decorated-Al203-supported Ni and NiB catalysts. Applied Catalysis. A, General,... 

Zhang, Y., Xiong, G., Sheng, S., and Yang, W. Deactivation studies over Ni0/y-Al203 catalysts for partial oxidation of methane to syngas. Catalysis Today, 2000, 63, 517. 

Yang, S., Kondo, J.N., Hayashi, K., Hirano, M., Domen, K., and Hosono, H. Partial oxidation of methane to syngas over promoted C12A7. Applied Catalysis. A, General, 2004, 277, 239. 

Chu, W., Yang, W., and Lin, L. The partial oxidation of methane to syngas over the nickel-modified hexaaluminate catalysts BaNiyAl12y0196. Applied. Catalysis. A, General, 2002, 235, 39. 

The catalytic partial oxidation of methane to syngas was first reported by Pettree as early as 1946 [1]. More recently, several investigators have studied the reaction mostly on Ni supported catalysts [2-4] and on Ru oxides [5]. In the past several years, Schmidt and coworkers [6-8] have studied the reaction using various noble metals in a monolith reactor. In this configuration, high methane conversions and syngas selectivities were achieved in a reactor operated under autothermal conditions... 

Slagten and Olsbye [ 10] studied the perovskite LaCoO, (containing some impurities of La O, and COiOj) for the partial oxidation of methane to syngas and observed the production of mainly CO,. If the catalyst was kept at 1073 K after 30 h on-stream the activity changed to give mainly CO which they assigned to the in situ reduction of cobalt. The XRD for Nd-Co-O after reaction revealed the presence of the phases Nd,0, and also the perovskite NdCoO,. For all used catalysts no clear evidence for the presence of simple cobalt oxides such as CoO, COjO, and CO3O4 could be found by XRD. 

The introduction of the catalyst presents one of the main problems in using MSRs for heterogeneously catalyzed reactions. There are some examples of reactors that are constructed directly from the catalytically active material. Kestenbaum et al. [145] used silver foils for the construction of a microchannel reactor for the partial oxidation of ethene to oxirane. A similar concept was proposed by Fichtner et al. [91,146], These authors used a microstructured rhodium catalyst for the partial oxidation of methane to syngas. This reaction can be considered as a coupling of the exothermic oxidation and the endothermic reforming of methane, which occur at different reaction rates. In such a case, the formation of a pronounced axial temperature profile can be avoided through the use of a material with high thermal conductivity. The reactor... 

According to Choudhary et al. (1996a) the following reactions are expected to occur simultaneously in the partial oxidation of methane to syngas (POM) ... 

The use of membrane reactors is still in its infancy. In recent years, these reactors using mixed-oxide catalysts have been used in the oxidative coupling and partial oxidation of methane to syngas. There is ample opportunity to extend these studies to achieve a much better understanding of these systems. Besides, there are other applications such as the selective oxidation of both hydrocarbons and oxygenates that deserve attention. It has... 

Use of the Reaction to Modify the Membrane and Improve Driving Force -The use of dense oxide membranes to feed O2 to partial oxidation reactions is limited by the need for high temperatures to obtain reasonable permeation rates. The potential exists for selectivity gains and the control of heat effects. One application where dense membranes have a clear role to play is in methane activation. In particular, the partial oxidation of methane to syngas. 

Diethehn S., Sfeir J., Clemens F., Van herle J., Favrat D., Planar and tubular perovskite-type membrane reactors for the partial oxidation of methane to syngas , J Solid State Electrochem (8) (2004)611-617. 

Tan, X. and Li, K. (2009) Design of mixed conducting ceramic membranes/reactors for the partial oxidation of methane to syngas. AIChE Journal, 55 (10), 2675-2685. 

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