Methane routes

Both of these suggestions are defective because of the absence of methane (route A) and the much greater quantities of TMMD produced compared with DMA (route B with Reaction 19 as the precursor of methylmethylene imine). A further route to TMMD could be provided by methylene insertion into the NN bond of TMH. This, though theoretically feasible, seems unlikely and requires the production of methylene from dimethylamino radicals by a surface reaction. The radical decomposition reactions (29 and 30) proposed by Gesser, MuUhaupt, and Griffiths (15) are not confirmed by our results. 

A study of the di-Ti-methane reactivity of the barrelene derivatives (73) in zeolites has been published. The reaction in a slurry affords a 77 23 mixture of (74) and (75) when the reaction is carried out in a zeolite the cyclooctatetraene product is suppressed and the two products are obtained in a ratio of 1 99. This enhancement of the di-Ti-methane reactivity occurs with Li" - and Na -exchanged zeolites.Liao and co-workers have reported new reactivity of some barrelenes. The reactions encountered are sensitive to substitution pattern. Thus, the irradiation of (76) with electron withdrawing groups follows the di-TT-methane route, to yield (77) and (78) predominantly. The less heavily substituted derivative (79) behaves differently, and irradiation affords (80) and (81) by the aza-di-7r-methane rearrangement, with (82) formed only in small amounts by the alternative di-Ti-methane path. Calculations have been used to examine the mechanism of the barrelene-semibullvalene isomerization. These results indicate that two biradical intermediates are involved in the T state. Other calculations on the di-Ti-methane rearrangement of barrelene substantiate the Zimmerman mechanism for the sensitized rearrangement. 

Of di-7c-methane and oxa-di-7t-methane rearrangements reported, that of greatest preparative value involves the photolysis of bicyclo[2,2,2]octadienones. The triplet-state reactions of these latter compounds have been examined for the first time in the absence of benzannelation. Bicyclo-octadienones (42) have available to them four di-7t-methane and two oxa-di-ii-methane modes of rearrangement, and, remarkably, only one di-7c-methane route is followed, to give (43) regiospecifically and in good (40—70 %) yields. 

The production of chloromethane (methyl chloride), dichloromethane (methylene chloride), and chloroform is carried out in one process, the hot radical chlorination of methane [route (a) in Topic 5.3.5 for mechanistic details see Section 2.2]. The process yields a mixture of all the different chloromethanes including the least desired tetrachloromethane. The chlorination reaction is initiated at above 250 °C. This temperature represents the lower temperature limit for the formation of chlorine radicals Cl by thermal decomposition of CI2 in sufficient quantity. During the... 

A mixture of the two reactants carbon monoxide and hydrogen is called synthesis gas and IS prepared by several processes The most widely used route to synthesis gas employs methane (from natural gas) and gives a 3 1 hydrogen to carbon monoxide ratio... 

The elimination of alcohol from P-alkoxypropionates can also be carried out by passing the alkyl P-alkoxypropionate at 200—400°C over metal phosphates, sihcates, metal oxide catalysts (99), or base-treated zeoHtes (98). In addition to the route via oxidative carbonylation of ethylene, alkyl P-alkoxypropionates can be prepared by reaction of dialkoxy methane and ketene (100). 

One possible route is to make formaldehyde direcdy from methane by partial oxidation. This process has been extensively studied (106—108). The incentive for such a process is reduction of raw material costs by avoiding the capital and expense of producing the methanol from methane. 

Direct conversion of methane [74-82-8] to methanol has been the subject of academic research for over a century. The various catalytic and noncatalytic systems investigated have been summarized (24,25). These methods have yet to demonstrate sufficient advantage over the conventional synthesis gas route to methanol to merit a potential for broad use. 

Aliphatics. Methane, obtained from cmde oil or natural gas, or as a product from various conversion (cracking) processes, is an important source of raw materials for aliphatic petrochemicals (Fig. 10) (see Hydrocarbons). Ethane, also available from natural gas and cracking processes, is an important source of ethylene, which, in turn, provides more valuable routes to petrochemical products (Fig. 11). 

A novel route to ammonia synthesis using methane, but without first producing hydrogen, has been proposed (101). 

G s-Ph se Synthesis. A gas-phase synthesis route to making fine, pure SiC having controllable properties has been described (78,79). Methane was used as a carbon source if required, and the plasma decomposition of three feedstocks, siUcon tetrachloride [10026-04-7] SiCl, dimethyl dichi orosilane, and methyltrichlorosilane [75-79-6] CH Cl Si, into fine SiC powders was investigated. 

The earliest method for manufacturiag carbon disulfide involved synthesis from the elements by reaction of sulfur and carbon as hardwood charcoal in externally heated retorts. Safety concerns, short Hves of the retorts, and low production capacities led to the development of an electric furnace process, also based on reaction of sulfur and charcoal. The commercial use of hydrocarbons as the source of carbon was developed in the 1950s, and it was still the predominate process worldwide in 1991. That route, using methane and sulfur as the feedstock, provides high capacity in an economical, continuous unit. Retort and electric furnace processes are stiU used in locations where methane is unavailable or where small plants are economically viable, for example in certain parts of Africa, China, India, Russia, Eastern Europe, South America, and the Middle East. Other technologies for synthesis of carbon disulfide have been advocated, but none has reached commercial significance. 

Catalytic reactions at somewhat lower temperatures also produce ethylene and other olefins. When coupled with a methane process to methyl chloride, this reaction results ia a new route to the light hydrocarbons that is of considerable interest. 

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. 

The gas and liquid are separated in the cold separator, which is a three-phase separator. Water and glycol come off the bottom, hydrocarbon liquids are routed to the distillation tower and gas flows out the top. If it is desirable to recover ethane, this still is called a de-methanizer. If only propane and heavier components are to be recovered it is called a de-etha-nizer. Tiie gas is called plant residue and is the outlet gas from the plant. 

The gas is routed through heat exchangers where it is cooled by the residue gas, and condensed liquids are recovered in a cold separator at appro.ximately -90°F. These liquids are injected into the de-methanizer at a level where the temperature is approximately -90°F. The gas is (hen expanded (its pressure is decreased from inlet pressure to 22.3 psig) through an expansion valve or a turboexpander. The turboexpander Lises the energy removed from the gas due to the pressure drop to drive a compressor, which helps recompress the gas to sales pressure. The cold gas f-)50°F) then enters the de-methanizer column at a pressure and temperature condition where most of the ethanes-plus Lire in the liquid state. 

Apart from the carbene-1,2-addition route starting from 1,3-dienes, vinylcyclo-propanes may be obtained from 1,4-dienes through a di-n-methane rearrangement. 

This process is only of historical interest, because not more than 5 % of the blacks are produced via this route. In this process, the feed (e.g., natural gas) is burned in small burners with a limited amount of air. Some methane is completely combusted to carbon dioxide and water, producing enough heat for the thermal decomposition of the remaining natural gas. The two main reactions could be represented as ... 

Hydrogen sulfide, a coproduct, is used to recover sulfur by the Claus reaction. A CS2 yield of 85-90% based on methane is anticipated. An alternative route for CS2 is by the reaction of liquid sulfur with charcoal. However, this method is not used very much. 

Compound 13a can been obtained via two different routes firstly in the reaction of 11 with dimethyl aluminum chloride where LiCl is eliminated and secondly by the reaction of di(pyridyl) phosphane 12 (Py2PH) with trimethyl aluminum where methane is formed, (Scheme 5). The X-ray structure determination of [Me2AlPy2P] 13a, (Fig. 3) elucidates the aluminum atom to be coordinated by the two nitrogen atoms of the pyridyl rings in addition to the two remaining methyl groups leaving the aluminum four... 

Of bromochloromethanes reacting mainly at C— Br bonds, bromotrichloro-methane has been the most investigated compound. Both the various monomers and diversified routes of initiations were used in the studies of CCl3Br. The addition of bromotrichloromethane to a-olefines under common conditions of radical initiation has been described by a number of examples (ref. 3). 

Direct conversion of methane to ethane and ethylene (C2 hydrocarbons) has a large implication towards the utilization of natural gas in the gas-based petrochemical and liquid fuels industries [ 1 ]. CO2 OCM process provides an alternative route to produce useful chemicals and materials where the process utilizes CO2 as the feedstock in an environmentally-benefiting chemical process. Carbon dioxide rather than oxygen seems to be an alternative oxidant as methyl radicals are induced in the presence of oxygen. Basicity, reducibility, and ability of catalyst to form oxygen vacancies are some of the physico-chemical criteria that are essential in designing a suitable catalyst for the CO2 OCM process [2]. The synergism between catalyst reducibility and basicity was reported to play an important role in the activation of the carbon dioxide and methane reaction [2]. 

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