Oxygen of methane

The Bunsen burners in your labs are fueled by natural gas, which is mostly methane, CH The thermochemical equation for the combustion (burning in oxygen) of methane is... 

The CoPd/HMOR three-function catalyst is able to produce by itself mild oxygenates of methane, CH3OH and HCHO, above 100°C (373 K), as seen in Figure 5.6. It can be... 

It should be mentioned that with superacidic electrophilic oxygenation of methane either to methanol (with protonated hydrogen peroxide) or to formaldehyde (with protonated ozone), the products formed are indeed the protonated products (CH3OH2 and CH2=OH+, respectively), which are protected from further electrophilic oxygenation, which happens only too readily in conventional oxidations. 

Oxygenation of methane and higher hydrocarbons, that is, the production of valuable products through C—H activation, is an area of continuing interest.1065-1070... 

U. Balachandran, J.T. Dusek, R.L. Mieville, R.B. Poeppel, M.S. Kleefisch, S. Pei, T.P. Kobylinski, C.A. Udovich and A.C. Bose, Dense ceramic membranes for partial oxygenation of methane. Paper presented at the 3rd International Congress on Inorganic Membranes, July 10-14,1994, Worcester, MA, USA. 

Following up on their earlier report of surprisingly selective mercury-catalyzed oxidation of methane to methyl bisulfate by sulfuric acid (which was also the reaction medium) [52], Periana and coworkers discovered that a bipyrimidine complex of Pt(II) worked even better, generating the same product in over 70% yield - a remarkable achievement, given that selective oxygenation of methane to methanol or derivatives thereof rarely surpasses yields of a few percent. A mechanism closely akin to that of the Shilov system was proposed (Scheme 15), with SO3 replacing Pt(IV) as the oxidant to convert RPt(II) to RPt(IV) whether the initial C-H activation involved an RPt(IV)H intermediate or not was left an open question [52]. 

The selective oxygenation of methane and light alkanes (Ci-Cj) by the Fe(II)/H202 Fenton system was performed in the three-phase catalytic membrane reactor, enabling simultaneous reaction and product separation. Frusteri et al. reported that Nafion-based catalytic membranes catalyze the selective oxidation of... 

The superacid-catalyzed electrophile oxygenation of saturated hydrocarbons, including methane with hydrogen peroxide (via H302 ) or ozone (via HOs ), allowed the efficient preparation of oxygenated derivatives. 

Fischer-Tropsch Process. The Hterature on the hydrogenation of carbon monoxide dates back to 1902 when the synthesis of methane from synthesis gas over a nickel catalyst was reported (17). In 1923, F. Fischer and H. Tropsch reported the formation of a mixture of organic compounds they called synthol by reaction of synthesis gas over alkalized iron turnings at 10—15 MPa (99—150 atm) and 400—450°C (18). This mixture contained mostly oxygenated compounds, but also contained a small amount of alkanes and alkenes. Further study of the reaction at 0.7 MPa (6.9 atm) revealed that low pressure favored olefinic and paraffinic hydrocarbons and minimized oxygenates, but at this pressure the reaction rate was very low. Because of their pioneering work on catalytic hydrocarbon synthesis, this class of reactions became known as the Fischer-Tropsch (FT) synthesis. 

Medium Heat- Value Gas. Medium heat-value (medium Btu) gas (6,7) has a heating value between 9 and 26 MJ/m (250 and 700 Btu/fT). At the lower end of this range, the gas is produced like low heat-value gas, with the notable exception that an air separation plant is added and relatively pure oxygen (qv) is used instead of air to partially oxidize the coal. This eliminates the potential for nitrogen in the product and increases the heating value of the product to 10.6 MJ /m (285 Btu/fT). Medium heat-value gas consists of a mixture of methane, carbon monoxide, hydrogen, and various other gases and is suitable as a fuel for industrial consumers. 

The process can be operated in two modes co-fed and redox. The co-fed mode employs addition of O2 to the methane/natural gas feed and subsequent conversion over a metal oxide catalyst. The redox mode requires the oxidant to be from the lattice oxygen of a reducible metal oxide in the reactor bed. After methane oxidation has consumed nearly all the lattice oxygen, the reduced metal oxide is reoxidized using an air stream. Both methods have processing advantages and disadvantages. In all cases, however, the process is mn to maximize production of the more desired ethylene product. 

The cracked gas composition is shown ia Table 10 for the water queach operatioa (16). Oae thousand cubic meters of methane and 600 m of oxygen produce 1800 m of cracked gas. If a naphtha quench is used, additional yields are produced, consuming 130 kg of naphtha/1000 of methane... 

Total Hydrocarbon Gontent. The THC includes the methane combined in air, plus traces of other light hydrocarbons that are present in the atmosphere and escape removal during the production process. In the typical oxygen sample, methane usually constitutes more than 90% of total hydrocarbons. The rest may be ethane, ethylene, acetylene, propane, propylene, and butanes. Any oil aerosol produced in lubricated piston compressor plants is also included here. 

In one study, a coarse-grained sand aquifer was injected with methane and oxygen to stimulate the production of methane monooxygenase (MMO) enzyme which is capable of degrading TCE (18). TCE, added at 60—100 )-lg/L, was degraded by 20—30%. Injected concentrations of methane and oxygen were approximately 20 mg/L and 32 mg/L, respectively. 

Chlorination of Methane. Methane can be chlorinated thermally, photochemicaHy, or catalyticaHy. Thermal chlorination, the most difficult method, may be carried out in the absence of light or catalysts. It is a free-radical chain reaction limited by the presence of oxygen and other free-radical inhibitors. The first step in the reaction is the thermal dissociation of the chlorine molecules for which the activation energy is about 84 kj/mol (20 kcal/mol), which is 33 kJ (8 kcal) higher than for catalytic chlorination. This dissociation occurs sufficiendy rapidly in the 400 to 500°C temperature range. The chlorine atoms react with methane to form hydrogen chloride and a methyl radical. The methyl radical in turn reacts with a chlorine molecule to form methyl chloride and another chlorine atom that can continue the reaction. The methane raw material may be natural gas, coke oven gas, or gas from petroleum refining. 

Oxychlorination of Methane. The oxychlorination of methane with HCl and oxygen has received some attention since the 1970s (22—24), though there are no examples of an industrial process. This can be a coproduct process making all the chloromethanes in significant yields or one that makes primarily methyl chloride. Interest in this route has increased in the past few years because of progress in the methane to light hydrocarbons process. 

C. Oxygen and steam are also injected above the bed to increase carbon conversion and reduce yields of methane and other hydrocarbons. The freeboard 2one above the bed operates as much as 150 to 230°C above the bed temperatures (24). 

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