Methane Laboratory preparation

Laboratory Preparation of Methane.— As it is not practicable to obtain naturally occurring methane for study, we must resort to labora-... 

In the laboratory preparation of diketene the mixture of ketene, unchanged acetone, and methane from a ketene generator is passed into a condensing system which is cooled initially in Dry Ice, and the condensate is allowed to warm to room temperature over a period of about twenty-four hours. The resulting mixture of acetone, diketene, and dehydracetic acid is separated by distillation under reduced pressure (50-55% of diketene). More exact control of the concentration and... 

Although fire damp/ which is mainly methane, and choke damp (carbon dioxide) are frequent causes of mine accidents, Dr. William Brownrigg learned how to make good use of them. In 1741 he communicated to the Royal Society several papers on the gases of coal mines, but preferred to withhold them from publication until he could prepare a comprehensive treatise on the subject. His laboratory at Whitehaven was provided with several gas furnaces of his own design and a constant supply of fire damp from the nearby mines. Because of his skill in foretelling explosions by the rapid fall of the barometer, mine operators often consulted him. 

Tritium Analysis. Figure 13 shows the laboratory equipment used for sample preparation and counter filling. The bomb converter is designed to prepare methane for both carbon-14 and tritium analysis. The chemical reactions are ... 

Tonkovich et al. [81] compared the performance ofa commercial ruthenium/zirconia powder catalyst from Degussa with a laboratory-made ruthenium/zirconia catalyst prepared on a nickel foam monolith for the water-gas shift reaction. Methane formation occurred for the powder catalyst, which was much less pronounced for the monolith. The selectivity towards methane could be reduced at shorter residence times. However, the activity of the laboratory-made catalyst was lower, which was partially attributed to the lower catalyst mass (modified residence time). 

When this appendix was in preparation, methane electrochemical oxidation had not been achieved. A reformer was essential That fact influenced the author s choice of initial calculation route for the methane chemical exergy, to be via oxidation via an equilibrium reformer. Meanwhile direct oxidation has been achieved in the laboratory, as mentioned in Section A.3.2 (route 1). 

Ketene, H,C = C = 0, has been obtained by the pyrolysis of many compounds containing the CHjCO—group. However, its preparation from acetone has been the most successful from the standpoint of the laboratory and is carried out by passing the vapors through a combustion furnace at 650° (30%) or over a hot Chromel A wire filament at 700-750° (90%). The product is contaminated with ethylene, carbon monoxide, and methane. It may be purified by dimerization followed by depolymerization (cf. method 246). More often than not, since ketene dimerizes readily, it is passed directly from the generator into a reaction vessel for immediate consumption. 

Rejtrmces. Blicke and Burckhalter, J. Am. Chem. Sec., 44, 478 (1942). The method has been checked in the Socony-Vacuum Laboratories. In cases where di-(2-thienyl)methane can be conveniently separated irom the end-products, the crude reaction mixture can be conveniently utilized without resorting to distillation of the 2-thenyl chloride. Over-all yields normally are improved in this manner. The author has found that it is convenient to prepare this compound using equimolar quantities of hydrochloric acid, thiophene, and formaldehyde, omitting the use of hydrogen chloride. The yields tire comparable when the above proced ire is employed. 

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 ... 

The oxidation of haiogenated methanes by SO 3 is particuiariy worthy of mention. By choice of the halogen substituents, each of the more common carbonyl dihalides, both symmetrical and asymmetrical, can be prepared by a convenient laboratory method. For the synthesis of carbonyl difluoride, the reagents CF Clj or CF Br may be used. The addition of CFjBtj (0.5 mol) to SO 3 (2.5 mol) at 35-44 C over 2 h resulted in a yield (based on CFjBrj) of COFj of 63 %, according to [1875] ... 

Chemistry Due to its high toxicity, when needed for laboratory use, it is common for HCN to be used in situ. A typical procedure employing potassium cyanide and dilute sulfuric acid is outlined by Streitwieser and Heathcock (1976). A synthesis using sodium cyanide and sulfuric acid is available (Ziegler, 1941). HCN can be prepared commercially by several routes, including the reaction of ammonia/air with methane. 

In the di-7C-methane rearrangement example presented by M. Demoth the normal equipment of preparative laboratories is used, i.e. the suspension of chiral crystals ate irradiated in a Rayonet reactor leading to two isomers both in optically pure form. 

Tris(4-Chlorophenyl)methanol has been recovered from samples of marine mammals and bird eggs from the Arctic, the Antarctic, Australia, and North America (Jarman et al. 1992), and both this and the corresponding methane in a range of biota from the Baltic Sea coast (Falandysz et al. 1999). Tris(4-Chlorophenyl)methanol is probably a transformation product of tris (4-chlorophenyl)methane that has been prepared in the laboratory as a by-product of the procedure used commercially for DDT, and that has been detected in samples of technical DDT as well as in samples of biota (Buser 1995). 

A convenient laboratory method of preparing methane is to heat sodium acetate with soda lime, which is a mixture of sodium and calcium hydroxides. As organic acids or their salts are frequently used in the preparation of other compounds, it is well at this point to give a few facts about them. Acetic acid, which is described in detail in section 103, is the acid contained in vinegar. It has the structure represented by the formula... 

Preparation. In the laboratory methane can be prepared by hydrolysis of aluminum carbide (Al Cj) or to a lesser extent beryllium carbide (Be C) or by decomposing sodium acetate with sodium hydroxide. Carbon reacts with pure hydrogen to yield methane at temperatures above 1100°C but the reaction becomes noticeable only above 1500°C. In addition, a catalyst must be used to prevent the formation of acetylene. Commercially methane is only obtained from natural gas (see Section 17.5) or from fermentation of cellulose or sewage sludges. 

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