Methane manufacturing methods

The original method for the manufacture of ethyne, the action of water on calcium carbide, is still of very great importance, but newer methods include the pyrolysis of the lower paraffins in the presence of steam, the partial oxidation of natural gas (methane) and the cracking of hydrocarbons in an electric arc. 

The manufacture of the highly pure ketene required for ketenization and acetylation reactions is based on the pyrolysis of diketene, a method which has been employed in industrial manufacture. Conversion of diketene to monomeric ketene is accompHshed on an industrial scale by passing diketene vapor through a tube heated to 350—600°C. Thus, a convenient and technically feasible process for producing ketene uncontaminated by methane, other hydrocarbons, and carbon oxides, is available. Based on the feasibiHty of this process, diketene can be considered a more stable form of the unstable ketene. 

Another method of manufacturing SiC by the decomposition of a gas mixture containing silane, propane, and hydrogen, and hydrogen chloride has been described (80). With such a mixture, it was possible to work at a relatively lower (1200°C) temperature and it was claimed that compact, homogeneous P SiC crystals were obtained. In a variation of this gas-phase synthesis theme, SiC has been produced from the reaction of SiCl and methane (81). SiC precipitates from 1000 to 3000°C. 

Chloroform can be manufactured from a number of starting materials. Methane, methyl chloride, or methylene chloride can be further chlorinated to chloroform, or carbon tetrachloride can be reduced, ie, hydrodechlorinated, to chloroform. Methane can be oxychlorinated with HCl and oxygen to form a mixture of chlorinated methanes. Many compounds containing either the acetyl (CH CO) or CH2CH(OH) group yield chloroform on reaction with chlorine and alkali or hypochlorite. Methyl chloride chlorination is now the most common commercial method of producing chloroform. Many years ago chloroform was almost exclusively produced from acetone or ethyl alcohol by reaction with chlorine and alkali. 

The third and now preferred method of acetic acid manufacture is the carbonylation of methanol (Monsanto process), involving reaction of methanol and carbon monoxide (both derived from methane). This is discussed in Chapter 12, Section 3. 

Although we have included acetic acid manufacture under ethylene derivatives, as you can see it is made from three of the seven basic organics ethylene, C4 hydrocarbons, and methane, with the most important method being from methane. Pure 100% acetic acid is sometimes called glacial acetic because when cold it will solidity into layered crystals similar in appearance to a glacier. It is a colorless liquid with a pungent, vinegar odor and sharp acid taste, bp 118°C, and mp 17°C. 

Chlorination of Alkanes. The most direct and economical method for the manufacture of chloromethanes is the thermal free-radical chlorination of methane.176 177 Whereas in the 1940s and 1950s photochlorination was practiced in some plants, thermal chlorination is the principal industrial process today. The product chloromethanes are important solvents and intermediates. Commercial operations perform thermal chlorination at about 400-450°C. Vapor-phase photochemical chlorination of methane may be accomplished at 50-60°C. Fast and effective removal of heat associated with thermally induced free-radical substitution is a crucial point. Inadequate heat control may lead to explosion attributed to the uncontrollable pyrolysis liberating free carbon and much heat ... 

Methylene dichloride and chloroform may be produced by modified methods using a mixture of chlorine, methane, and methyl chloride as feed. Chlorination is run at 350-400°C reactor temperature at slightly above atmospheric pressure. A 2.6 1 chlorine methane ratio results in an optimal yield of chloroform. Alternatively, excess methane is reacted with chlorine at 485-510°C to produce methylene dichloride as the main product.181 The predominant method, however, still is the chlorination of methyl chloride manufactured by the reaction of methyl alcohol and hydrogen chloride.181... 

The earliest method for manufacturing carbon disulfide involved synthesis from the elements by reaction of sulfur and carbon as hardwood charcoal in externally healed retorts. Safely concerns, short lives of the retorts, and low produciion 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. 

In recent years hydrogen cyanide (HCN) has been replaced by ammonia as u raw material for producing acrylonitrile. A large portion of hydrogen cyanide is used in (he manufacture of methyl methacrylate, adiponitrile, and sodium cyanide. The preferred method of manufacturing hydrogen cyanide is to react methane, ammonia, and air over a platinum catalyst at a temperature above lOOri C... 

At a time when the only practicable methods for the preparation of nitromethane were the interaction of methyl iodide with silver nitrite and the Kolbe reaction from chloracetic acid, the explosive was far too expensive to merit consideration. The present cheap and large scale production of nitromethane by the vapor-phase nitration of methane and of ethane has altered the situation profoundly. Trimethylolnitromethane trinitrate is an explosive which can now be produced from coke, air, and natural gas. Nitromethane too has other interest for the manufacturer of explosives. It may be used as a component of liquid explosives, and it yields on reduction methylamine which is needed for the preparation of tetryl. 

One method for the manufacture of synthesis gas is the catalytic reforming of methane with... 

Application of the method to the determination of the dihydroergotoxine alkaloids in commercial samples and pharmaceutical preparations were all carried out with the free base of the alkaloids since analysis of their salts cannot be performed without excessive decomposition. The mean dihydroergotoxine methane sulphonate content of five commercial samples was 95,2 2.9 %, including a mean dihydroergocomine content of 30.9 0.8 %, a mean dihydro-ergokryptine content of 32.8 2.1 % and a mean dihydroergocristine content of 31.5 3.5 %. Almost the same data were observed for dihydroergotoxine tablets obtained from two manufacturers. 

The dismutation reaction is potentialiy of some industrial significance. One of the general methods for the manufacture of tetrachloromethane is the chlorination of methane [2165] ... 

The use of natural gas for manufacture of various chemicals via the syngas route or via direct methanation or via other miscellaneous methods is very important for chemical industries. However, the production of all the desired chemicals is accompanied by formation of byproducts and some end products, which when released into the environment constitute pollution hazards. 

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