Methane, catalytic conversion

Methane catalytic conversion into carbon and hydrogen was examined over nickel-containing pentasil zeolites in a vacuum-circulation laboratory unit [4] at a catalyst/feed mass ratio of 5.0 and within a temperature range of 743 - 843 K. 

The increased catalytic reactivity of methane on Pt at elevated pressures allows for significant fuel consumption at lower wall temperatures than those required at atmospheric pressure, thus facilitating an earlier microreactor ignition. This is evidenced in Figs. 8.6 and 8.7, where streamwise methane catalytic conversion rates and channel wall temperature profiles are plotted for Cases 1 and 5, atp = 1 and 5 bar, respectively. 

Fig. 8.6 Methane catalytic conversion rates along the microreactor during the startup phase for Cases 1 (bottom graph) and 5 (top graph), at 4 time instances ignition (ign), steady state (st) and two intermediate times. Cordierite wall material...

Fig.7. Scheme of thermsil catalytic conversion and utilization of solar energy based on reversible methane reforming / methanation reactions. 

Methane reforming reaction is accomplished under the action of heat collected from mirror concentrator of solar light. The mixture of CO and H2 produced in this reaction can be stored and then, when necessary, converted into high-potential heat (with the temperature up to 950 K) in the methanation catalytic reactor. The efficiency of solar-to-chemical energy conversion as high as... 

When the temperature of a carbonate reservoir that is saturated with high-viscosity oil and water increases to 200° C or more, chemical reactions occur in the formation, resulting in the formation of considerable amounts of CO2. The generation of CO2 during thermal stimulation of a carbonate reservoir results from the dealkylation of aromatic hydrocarbons in the presence of water vapor, catalytic conversion of hydrocarbons by water vapor, and oxidation of organic materials. Clay material and metals of variable valence (e.g., nickel, cobalt, iron) in the carbonate rock can serve as the catalyst. An optimal amount of CO2 exists for which maximal oil recovery is achieved [1538]. The performance of a steamflooding process can be improved by the addition of CO2 or methane [1216]. 

Preliminary results of methane catalytic combustion indicated that Pt/H-MCM-22 sample showed a 100% conversion at 700°C with 100% selectivity toward the C02 formation. The sample showed also high thermal stability in fact, the catalytic activity was preserved after heating overnight at 800°C under air flow. (Catalytic data kindly provided by Ing. R. Pirone, Istituto di Ricerche sulla Combustione Italian CNR). 

Methane has also been used as the reducing agent in the catalytic conversion of NO to N2 over Co-ZSM-5 zeolites [75] in the presence of oxygen. The high NO conversions (>70%) were achieved by microwave irradiation at 250-400 °C, whereas under similar conditions thermal runs failed to convert either NO or methane in significant amounts. The high activity and selectivity of the reduction of NO by methane achieved with microwave irradiation was probably because of the activation of methane to form methyl radicals at relatively low reaction temperatures. 

Catalytic Conversion of Methane to Synthesis Gas by Partial Oxidation... 

M. A. Gondal, A. Hameed, and A. Suwaiyan, Photo-catalytic conversion of methane into methanol using visible laser, Appl. Catal. A 243(1), 165-174 (2003). 

Nazarkina, E. B. and N. A. Kirichenko 1979. Improvement in the steam catalytic conversion of methane by hydrogen liberation via palladium membranes Khim. Tekhnol. Topi. Masel. 3 5-10. 

The CH-activation of alkanes and especially of methane and their catalytic conversion to alcohols is one of the major challenges for chemists. Methane as the major part of natural gas is currently the cheapest source of hydrocarbons and the need for methanol will increase in the near future. Methane conversion to methanol would make a conveniently transportable fuel and also a new carbon source for the chemical industry. 

The direct catalytic conversion of methane has been actively pursued for many years. Much of the emphasis has been on the direct production of methanol via selective partial oxidation (8), coupling of methane to ethylene (9), or methane aromatization (10). At this time none of these technologies has been demonstrated commercially due to low yields of desired products due to combustion by-products or low equilibrium conversion at reasonable process temperatures and pressures. The potential benefits of a hypothetical process for the direct partial oxidation of methane to methanol (11) are presented as an example. 

Reaction X. (6) Catalytic Conversion o Simple Hydrocarbons into more Complex Hydrocarbons.—These reactions are usually accomplished at high temperatures in presence of catalysts. Acetylene, propylene and even methane can be converted into benzene. (E.P., 374,422 369,351 366,394.)... 

B) Let us consider a more complex example of a catalytic conversion of methane [51]... 

Compared with the common high-temperature conversion of natural gas and further carbon oxide conversion on a catalyst [131], the current process promotes process simplification the reaction is implemented at relatively low temperature (860-900 °C instead of 1400-1600 °C for existing non-catalytic processes of methane conversion) and an additional unit for catalytic conversion of carbon oxide is excluded (in NH3 production). 

The thermal and catalytic conversion of different hydrocarbon fractions, often with hydrotreating and other reaction steps, is characterized by a broad variety of feeds and products (Table 1, entry 4). New processes starting from natural gas are currently under development these are mainly based on the conversion of methane into synthesis gas, further into methanol, and finally into higher hydrocarbons. These processes are mainly employed in the petrochemical industry and will not be described in detail here. Several new processes are under development and the formation of BTX aromatics from C3/C4 hydrocarbons employing modified zeolite catalysts is a promising example [10],... 

F. R. Ribeiro M. Guisnet Eds. Nato AS. Series, Kluwer Academic Publishers, Dordrecht, The Netherlands, 1997 (c) Catalytic Conversion of Methane to More Useful Chemicals and Fuels a Challenge for the 21st Century. ... 

J. H. Lunsford, in L. Guczi, F. Solymosi, P. Tetenyi (Eds) The Catalytic Conversion of Methane to Oxygenates and Higher Hydrocarbons, Part A. Adademiai Kiado, Budapest, 1992. 

The interrelationships between activation of H2 and other a-bonded molecules such as alkanes and silanes are highly significant because catalytic conversion of methane and other alkanes is strongly being pursued (17-19). An important question thus is whether C-H bonds in alkanes, particularly CH4, can bind to superelectrophilic metal centers to form a a alkane complex that can be split heterolytically where proton transfer to a cis ligand (or anion) takes place followed by functionalization of the resultant methyl complex (Eq. (3)). 

Steam reforming refers to the endothermic, catalytic conversion of light hydrocarbons (methane to gasoline) in the presence of steam [see Eq. (5.1)]. The reforming reaction takes place across a nickel catalyst that is packed in tubes in an externally-fired, tubular furnace (the Primary Reformer). The lined chamber reactor is called the secondary reformer , and this is where hot process air is added to introduce nitrogen into the process. Typical reaction conditions in the Primary Reformer are 700°C to 830°C and 15 to 40 bar46. 

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