Preparation of methane
This synthesis description was provided by Fritz Haber.
2.5g of Sodium hydroxide is ground to a fine powder and mixed intimatly with finely powdered Sodium acetate. A test tube made of fused silica is charged with the resulting mixture. After stoppering the test tube with a one-holed stopper and a glass tube, heat is applied by means of a (bunsen) burner to the almost vertically held test-tube clamped by means of a stand. Soon the gas evolution starts. The Methane gas may be collected with a pneumatic trough. Alternatively, the Methane gas can directly be used for reactions like radical chlorination. This reaction may be scaled up as much as desired. If large amounts of Methane are to be prepared via this method, it is best to use a cleaned out paint can with a tight fitting lid. A hole is drilled into the lid which should be just large enough to fit a ground glass adapter (teflon tape may be used to ensure tight fitting). The other side of the adapter is then fitted with a rubber stopper with a glass tube, just as before. The glass adapter protects the rubber stopper from the heat of the metal can. The metal can is then heated from below with a (bunsen) burner. If necessary, steel balls could be mixed into the reaction mixture inside the metal can to improve heat transfer. (Note: The above mentioned amounts of reactants will generate about one liter of Methane gas (at 20°C)).
Reference: Prof. Römpp / Raaf: Organische Chemie im Probierglas, 14th edition (1975), Franckh Kosmos Verlag Stuttgart; p. 39-40
Preparation of methane from aluminum carbide
Aluminum carbide is spread over a layer of sand in a flask, which is fitted with a dropping funnel and delivery tube. Dilute hydrochloric acid is placed in a dropping funnel and slowly added dropwise to the flask with the aluminum carbide. In contact with diluted hydrochloric acid methane is evolved, and, after expelling the air from the flask and apparatus, may be collected over water. Generated methane could be additionally purified by passing through washing bottle with water in order to remove hydrochloric acid, then dried by passing through concentrated sulfuric acid, or anhydrous calcium chloride. The methane gas may be liquefied (boiling point -161.5° C), if liquid air or nitrogen is available.
A class-book of organic chemistry, by J. B. Cohen, 92, 1918
Preparation of methane from methyl iodide and methanol
To one limb of a wide U-tube cooled in water and filled with the zinc-copper, or the alumininm-mercury couple, is attached a small tap funnel, and to the other a small reflux condenser. The zinc-copper couple is prepared by placing 30 g of zinc in an aqueous solution of copper sulphate until the surface of the metal is covered with a film of metallic copper. The couple is washed with water and then with absolute alcohol. The aluminium-mercury couple, which gives a better yield of methane gas, is prepared by immersing 20 g of small pieces of sheet aluminium in mercuric chloride solution until a film of mercury covers the surface of the aluminium, which is washed as above. 100 ml (excess) of methyl alcohol (acidified with 2 drops of dilute sulphuric acid if the zinc-copper couple be used) are poured on to the couple in the U-tube and 50 g of methyl iodide are added gradually from the funnel so that the reaction does not become too violent nor the couple too hot. With the aluminium-mercury couple the reaction is especially vigorous, and good cooling is required. The gas is washed in worms containing (1) distilled water; (2) sodium methoxide dissolved in methyl alcohol – 2 worms; (3) distilled water; (4) fuming sulphuric acid – 2 worms; (5) conc. suIphuric acid – 2 worms ; (6) distilled water; (7) 50% caustic soda solution – 2 worms. Conc. suIphuric acid is used to condense the acid mist from the fuming sulphuric acid washings; distilled water is always inserted between worms containing liquids, which will react violently if mixed. The gas is then passed through a U-tube heated in boiling water and containing palladium black to absorb hydrogen, of which usually about 1% is present. Alternatively, palladium oxide may be used in the tube to oxidise the hydrogen. The gas is collected in a gas-holder over 50% aqueous glycerol, which does not dissolve methane, under a slight excess pressure. If the dry gas be required, it is collected over mercury or conc. suIphuic acid, being first dried by passage through two U-tubes containing phosphorus pentoxide. To free it completely from hydrogen three or four treatments with palladium or its oxide will be necessary. The gas obtained in this way is pure provided care be taken that all air has been swept out of the apparatus before collection is begun.
If liquid air is available, the hydrogen in the methane prepared above is best removed by fractional distillation.
The gas from the holder A is passed through a series of U-tubes containing phosphorus pentoxide, then through a small bulb B. When all the air has been driven out of the apparatus, a vacuum vessel containing liquid air is brought below B and gradually raised so as slowly to increase the cooled surface of the bulb. The methane condenses rapidly in B, hydrogen passing away through C. When A is almost empty of gas, the remainder is run away by means of the three-way tap D. Meanwhile the liquid air container is raised or lowered around B, so that the liquid in B gently boils. When about one-fifth has boiled away C is closed, and a small amount of gas allowed to pass away through D. Connection is then made to the gas-holder, which is slowly filled under a pressure slightly above atmospheric. If preferred, the methane may be distilled into another holder through C, and the gas from several holders, such as A, purified and collected in one holder. Great care must be taken in manipulating the liquid air container, so that the liquid in B boils gently; if the vacuum vessel be lowered too rapidly, vigorous boiling will occur, and a great pressure generated in the apparatus. The last traces of gas in B are not collected. This process can be repeated if a very pure gas is required. In each operation about one-third of the original gas is lost. The purity of the gas may be ascertained by inserting a platinum resistance thermometer in the liquefaction bulb, and determining the temperature during the operation, as in the fractional distillation of any other liquid. This is more important in preparing the higher hydrocarbons pure.
Systematic organic chemistry, by W. M. Cumming, 181-182, 1937.
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