HIGH TEMPERATURE CARBONIZATION OF COAL 409
Ethylene was found to show rather more stable properties than ethane, the quantity decomposed at 800 C. being 62 per cent, after heating for forty-five seconds, and at 1,100 C. no trace of the product remained. The decomposition products consisted largely of hydrogen and methane, with a very small proportion of acetylene at the lower temperature.
The experiments with benzene are of particular interest in that they indicate the stable nature of this product at low and moderate temperatures and its com-plete instability at higher temperatures. At 800° C. the decomposition was negligible, but at 1,100° C. a very different result was obtained.
Benzene, at 1,100° C., heated for forty-two' seconds.
Composition of gas. Before. After.
Benzene Methane Hydrogen Ethylene Acetylene 5-0 per cent. 47-8 47-2 „ nil nil nil 11-1 per cent. 88-4 nil Trace
In connection with benzene it is interesting to note the views of F. Haber,1 who considers that the aromatic hydrocarbons are disposed to form more complex molecules with the elimination of hydrogen. Thus two molecules of benzene give diphenyl:—
2 CeH6
+ W
<71 O
T. F. E. Rhead 2 states that benzene hydrocarbons produced during the dis-tillation of coal appear to be formed by three main groups of reactions, namely
(«) Condensation of olefines.
(&) Dehydrogenation of corresponding naphthenes.
(c) The polymerization of acetylene.
The same authority states that, if the necessary naphthenes predominated in the primary products of coal distillation, a temperature of 500° C. and upwards would give the maximnm yield of benzene hydrocarbons ; but apparently the olefines predominate because the maximum benzene yield is obtained at 700° C. and upwards.
J. W. Cobb,3 in a recent endeavour to determine how benzene and its homo-
a Ber., vol. 29, p. 2191. 2 Proc. Soc. Chem. Ind., July, 1917,
Proc. N. Brit. Assoen. Gas Managers, Sept., 1918.