Methane thermal oxidation

Recently, such a temperature oscillation was also observed by Zhang et al (27,28) with nickel foils. Furthermore, Basile et al (29) used IR thermography to monitor the surface temperature of the nickel foil during the methane partial oxidation reaction by following its changes with the residence time and reactant concentration. Their results demonstrate that the surface temperature profile was strongly dependent on the catalyst composition and the tendency of nickel to be oxidized. Simulations of the kinetics (30) indicated that the effective thermal conductivity of the catalyst bed influences the hot-spot temperature. 

Chlorinated derivatives of methane include methyl chloride, methylene chloride, chloroform, carbon tetrachloride, and several chlorofluorohydrocarbons (CFCs). We discuss carbon tetrachloride (CT) as a representative example of this group. CT was originally prepared in 1839 and was one of the first organic chemicals to be produced on a large scale by the end of the nineteenth century and beginning of the twentieth century. CT is the most toxic of the chloromethanes and the most unstable on thermal oxidation (Holbrook 2000). 

Fig. 11. The mechanical valves can be replaced by thermal or chemical modulating devices. In principle, this modification circumvents the need of reliable mechanical valves and offers a more flexible system s . An example is the thermal oxidative modulation of methane in air. Figure 12 shows a concentration profile during 8 days, determined with an experimental modulation CC set up...

Senkan [45] has illustrated this latter point by means of the destruction of trichloroethylene (C2HC13) in the presence of oxygen. The reaction begins at 600-700°C. When methane is also present, however, the thermal oxidation of trichloroethylene is inhibited to such an extent that its decomposition does not begin until temperatures of about 950°C are reached. C2HC13 destruction in the presence of 02 occurs by the following reaction ... 

Processes described in this chapter include (1) thermal oxidation of VOCs and odors, (2) catalytic oxidation of VOCs and odors, (3) catalytic oxidation of sulfur compounds to sulfur oxides, (4) catalytic conversion of organic sulfur compounds to hydrogen sulfide, (S) conversion of carbon monoxide to carbon dioxide (shift conversion), (6) conversion of oxides of carbon to methane (methanation), and (7) conversion of acetylene to ethylene (selective hydrogenation). 

Hydrogenation of the oxides of carbon to methane according to the above reactions is sometimes referred to as the Sabatier reactions. Because of the high exothermicity of the methanization reactions, adequate and precise cooling is necessary in order to avoid catalyst deactivation, sintering, and carbon deposition by thermal cracking. 

Although ethylene is produced by various methods as follows, only a few are commercially proven thermal cracking of hydrocarbons, catalytic pyrolysis, membrane dehydrogenation of ethane, oxydehydrogenation of ethane, oxidative coupling of methane, methanol to ethylene, dehydration of ethanol, ethylene from coal, disproportionation of propylene, and ethylene as a by-product. 

As mentioned in Chapter 2, methane is a one-carhon paraffinic hydrocarbon that is not very reactive under normal conditions. Only a few chemicals can he produced directly from methane under relatively severe conditions. Chlorination of methane is only possible by thermal or photochemical initiation. Methane can be partially oxidized with a limited amount of oxygen or in presence of steam to a synthesis gas mixture. Many chemicals can be produced from methane via the more reactive synthesis gas mixture. Synthesis gas is the precursor for two major chemicals, ammonia and methanol. Both compounds are the hosts for many important petrochemical products. Figure 5-1 shows the important chemicals based on methane, synthesis gas, methanol, and ammonia. ... 

Thermal Decomposition. The therm decompn was studied betw 380 and 430° and found to be homogeneous and apparently 1st order. The products were complex and included nitric oxide, methane, carbon monoxide, and w plus small amts of ethane, ethylene, and nitrous oxide (Ref 23)... 

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