Pyrolysis of methane

Methane can be converted directly to C2 hydrocarbons by thermal coupling or pyrolysis [175]. In most cases, pyrolysis means thermal decomposition that yields lighter hydrocarbons than the original. In this case, however, C chem- 

As discussed in Chapter 1, the proven world gas and oil resources show an increase in gas reserves and a leveling off of the oil resources. Most of these reserves are located distantly from the major consumption markets. This is one of the reasons why there is a great incentive to convert natural gas into petrochemicals and clean liquid fuels. 

All these processes interestingly but understandably have three things in common high temperature, short residence time, and rapid quenching. 

The reaction mechanisms for thermal coupling of methane has been studied by various researchers [175], The overall reaction in thermal coupling of methane can be described as a stepwise dehydrogenation at high temperature. 

The formation of products is explained by a free-radical formation. The initiation step and the formation of ethane are described by. 

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Flame or Partial Combustion Processes. In the combustion or flame processes, the necessary energy is imparted to the feedstock by the partial combustion of the hydrocarbon feed (one-stage process), or by the combustion of residual gas, or any other suitable fuel, and subsequent injection of the cracking stock into the hot combustion gases (two-stage process). A detailed discussion of the kinetics for the pyrolysis of methane for the production of acetylene by partial oxidation, and some conclusions as to reaction mechanism have been given (12). 

Outside the realm of typical hydrocarbon pyrolysis is the high temperature pyrolysis of methane. In one variant of this process, which has only been commercialized to produce acetylene (with some BTX), methane reacts in an electric arc at about 1500°C (17) with very short contact times. At higher temperatures or with a catalyst and added hydrogen, BTX is produced with fairly high selectivity (18). 

Pyrolysis of methane under the action of pulsed microwave radiation in the presence of solid catalysts has been reported by Russian authors [71, 72], The application of pulse microwave power was shown to be a promising means of production of hydrogen syngas, ethyne, and filament carbon. 

The mechanism of thermal decomposition (pyrolysis) of methane has been extensively studied [90,91]. Because C-H bonds in the methane molecule are significantly stronger than C-H and C-C bonds of the products, the secondary and tertiary reactions contribute at the very early stages of the reaction, which obscure the initial processes. According to Holmen et al. [92], the overall methane thermal decomposition reaction at high temperatures can be described as a stepwise dehydrogenation as follows ... 

It involves the displacement of hydrogen, or an alkyl group, from a saturated carbon atom by a methyl radical. For a methane pyrolysis, its history goes back to Kassels attempt to write a chain reaction for the pyrolysis of methane. The evidence for it is quite unsubstantial. 

The aim of our study is to investigate the chemical composition of the prepared catalyst Fe-MgO and to monitor structural changes of the catalyst during the pyrolysis of methane. 

Fast Pyrolysis of Methane in Tubular Reactor. We have conducted a series of experiments on fast pyrolysis of methane using ceramic (alumina) and quartz tubular reactors. 

M. Calahan, Catalytic pyrolysis of methane and other hydrocarbons, Proc. Conf. Power Sources, 26 ... 

Vapor phase co-pyrolysis of methane-ammonia mixtures at temperatures in the 1200-1400°C... 

There are good reasons to suppose that a similar phenomenon of fluidization of nanoparticles of the same catalytically active metals may happen to some other catalytic processes when they are accompanied by the formation of graphitized carbon. Examples of such processes are catalytic pyrolysis of methane... 

The feasibility of such synthesis is easy to demonstrate with pyrolysis of a hydrocarbon as an example, such as the pyrolysis of methane by stepwise reaction... 

One can see that diamond may be synthesized indeed through pyrolysis of methane under rather mild conditions. 

The underlying concept of this method for the synthesis of filamentous carbonaceous nanomaterials is fairly simple. As the temperature rises above a certain limit, which depends on the thermodynamic and kinetic para meters of carbon containing compounds, such as hydrocarbons, such compounds tend to pyrolyze in the air free conditions to form free carbon. For example, the noncatalytic pyrolysis of methane can be achieved at ambient pressure and at temperatures above 900—1000 K to produce soot (near spherical nanosized carbon particles) and hydrogen ... 

The CVD method used in this experiment to grow nanotubes was accomplished using the pyrolysis of methane, catalyzed by iron-doped alumina catalyst (Eq. 1). 

Li, Y.Y., Nomura, T., Sakoda, A., Suzuki, M. (2002b), Fabrication of carbon coated ceramic membranes by pyrolysis of methane using a modified chemical vapor deposition apparatus Journal of Membrane Science, 197,23-35. 

Diacetylene is formed as a significant by-product in the commercial synthesis of acetylene by the pyrolysis of methane and other hydrocarbons . Smaller amounts of triacetylene are also formed . Procedures have been devised for removing and recovering the diacetylenc - . 

The use of mass spectrometers suggests itself as a convenient method for the investigation of unstable reaction intermediates. The mass spectrometer can not only measure the concentration of an intermediate but also establish its chemical identity. Eltenton first applied the technique to the study of free radicals, and from the earliest experiments useful results have been obtained. Thus Eltenton in his first paper showed that the pyrolysis of methane on a carbon filament leads to the formation of methyl radicals, and not methylene 2is believed formerly, and he... 

Introduction. Acetylene has the empirical formula C2Hs. It shows a greater unsaturation than ethylene, in that it can add four univalent groups to each carbon atom. This xmsaturation is indicated by a triple bond between the two carbon atoms HC=CH. Acetylene is produced in the thermal decomposition of many hydrocarbons. Of theoretical interest is its formation from hydrogen and carbon in the electric arc. It is prepared industrially by the pyrolysis of methane, and by the action of water on calcium carbide. The last method is employed for preparation of small quantities in the laboratory ... 

Muradov N, Smith F, Huang C, Raissi AT (2006) Autothermal catalytic pyrolysis of methane as a new route to hydrogen production with reduced CO2 emissions. Catal Today 116 281-288... 

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