HIGH TEMPERATURE CARBONIZATION OF COAL 405
H
(1) H— C = C —H H — H
+ (2) H — C =. C — H gives 1 II
+ (3) TI— C = C — H H C. C— H
C
There is little doubt that such a reaction takes place to some extent, although, in the main, it seems probable that the benzene results at moderate temperatures from the paraffin derivatives. Bone has found that at low temperatures acetylene exhibits a strong tendency to polymerize, forming benzene, etc., so that when acetylene is the principal primary product in the decomposition of another hydrocarbon (for example, ethylene) there is always a marked secondary formation of benzene and otter aromatic hydrocarbons. This tendency towards polymerization reaches its maximum between 500° and 700° C. and practically ceases to exist above 1,000° C.
With regard to the actual method of decomposition of the hydrocarbons the work of Bone 1 may be looked upon as classical. This investigator propounded entirely new theories, based on the faet that carbonaceous residues, such as CH and CH2> are capable of an extremely fugitive existence. With the exception of methane, however, he is of the opinion that the mode of decomposition of any par-ticular hydrocarbon cannot be expressed by means of a single Chemical equation. The degradation of methane is, in the main, a direct disunion into carbon and hydrogen—CH4 = C + 2H2. The free carbon deposited from this reaction is of a hard and lustrous type, being wholly different from that resulting from the decomposition of the other hydrocarbons. So far as ethane and ethylene are concerned, the effeet of high temperatures is to cause a dissolution of the bonds uniting the carbon atoms, thus giving rise to the residues = CH and CH2, Bone states that these residues may subsequently—
(1) Meet with other similar residues and form H2C ~~ CH2 and HC = CH.
(2) Break down direetly into carbon and hydrogen.
(3) Be direetly hydrogenized into methane.
These three reactions may occur simultaneously, depending upon the temperature, pressure, and amount of hydrogen prevailing. In the case of ethane, Bone represents the changes in the following way:—
Ethane = H — C 'T7 C — H
H/ \h
1 J. Chem. Soc., 1908, p. 1197.