Methane, selective oxidation

Methane-Selective Oxidation of SUica-Supported Molybdenum (VI) Catalysts Structure and Catalytic Performance... 

Mauti, R. and Mims, C. (1993). Oxygen Pathways in Methane Selective Oxidation over SUica-snpported Molybdena, Catal. Lett., 21, pp. 201-207. 

Kongzhai L, Hua W, Yonggang W, et al. Preparation and characterization of Cel-xFex02 complex oxides and its catalytic activity for methane selective oxidation. J Rare Earths. 

A topic of current interest is that of methane activation to give ethane or selected oxidation products such as methanol or formaldehyde. Oxide catalysts are used, and there may be mechanistic connections with the Fischer-Tropsch system (see Ref. 285). 

Spectroscopy of the PES for reactions of transition metal (M ) and metal oxide cations (MO ) is particularly interesting due to their rich and complex chemistry. Transition metal M+ can activate C—H bonds in hydrocarbons, including methane, and activate C—C bonds in alkanes [18-20] MO are excellent (and often selective) oxidants, capable of converting methane to methanol [21] and benzene to phenol [22-24]. Transition metal cations tend to be more reactive than the neutrals for two general reasons. First, most neutral transition metal atoms have a ground electronic state, and this... 

Li/MgO(100) Mo(lOO) thin film (selective oxidation of methane to ethane) (7)... 

The large amounts of natural gas (mainly methane) found worldwide have led to extentive research programs in the area of the direct conversion of methane [1-3]. Ihe oxidative transformation of methane (OTM) is an important route for the effective utilization of the abundant natural gas resources. How to increase catalyst activity is a common problem on the activation of methane. The oxidation of methane over transition m al oxides is always high active, but its main product is CO2, namely the product of deep oxidation. It is because transition metal oxides have high oxidative activity. So, they were usually used as the main corrqtonent of catalysts for the conqilete oxidation of alkane[4]. The strong oxidative activity of CH4 over tran on metal oxides such as NiO indicates that the activation of C-H bond over transition metal oxides is much easier than that over alkaline earth metal oxides and rare earth metal oxides. Furthermore, the activation of C-H bond is the key step of OTM reaction. It is the reason that we use transition metal oxides as the mam conq>onent of the OTM catalysts. However, we have to reahze that the selectivity of OTM over transition metal oxides is poor. 

Selox [Selective oxidation] A process for selectively oxidizing methane to syngas using a proprietary heterogeneous catalyst at temperatures up to 1,000°C. Developed on a laboratory scale by TRW, CA, partly financed by the U.S. Department of Energy in 1983. 

Fig. 1. Relationship between catalyst temperature and reaction time in methane partial oxidation catalyzed by Ni/Si02 (temperature of the gas phase (a) 1019 K, (b) 899 K, (c) 809 K, (d) 625 K). The reaction was carried out in a fixed-bed reactor (a quartz tube of 2 mm inside diameter) at atmospheric pressure. Before reaction, the feed gas was allowed to flow through the catalyst undergoing heating of the reactor from room temperature to 1073 K at a rate of 25 K min-1 to ignite the reaction, and then the reactant gas temperature was decreased to the selected value. Reaction conditions pressure, 1 atm catalyst mass, 0.04 g feed gas molar ratio, CH4/O2 = 2/1 GHSV, 90,000 mL (g catalyst)-1 h-1) (25).

A number of system approaches can be used to clean up the fuel feed. These include pressure swing adsorption, membrane separation, methanation, and selective oxidation. Although selective oxidation does not remove CO2, it is usually the preferred method for CO removal because of the parasitic system loads and energy required by the other methods. In selective... 

Roos, J. A., S. J. Korf, J. J. P. Bicrmann, J. G. van Ommen and J. R. H. Ross. 1989. Oxidative coupling of methane, the effect of gas composition and process conditions. Proc. 2nd Europ. Workshop Meeting, New Developments in Selective Oxidation. Rimini, Italy. 

To further reduce the carbon monoxide, a preferential oxidation reactor or a carbon monoxide selective methanation reactor is used. The term selective oxidation is also used for preferential oxi-... 

Concerning the operation of catalysts under adiabatic conditions, Basini et al. [156] reported the results of methane partial oxidation runs in a pilot-scale reactor operating at high pressure and short contact times, showing stable activity (almost complete conversion of methane and over 90% selectivity to CO and H2) during more than 500 h on-stream. In addition, operability for 20 000 h bench-scale testing has been claimed recently by the same group [157]. 

Table Activity and Selectivity of Si02, 4% Mo03/Si02 and 5% 203/8102 Catalysts in Methane Partial Oxidation. Batch reactor data ...

---