THE DECOMPOSITION OF METHANE IN THE NEGATIVE GLOW

The decomposition of methane was studied in the negative glow of a d-c. discharge at pressures of 0.30 and 0.050 mm. The discharge tube was cooled by liquid or solid nitrogen.The main products were ethane, ethylene, and acetylene in addition to hydrogen and a nonvolatile product which appeared mainly on the cathode as a solid having the formula (CH) n . Smaller amounts of propane, propene, propyne, butane, butene, butadiene, and pentene were also found. Lowering the temperature of the discharge tube from −196° to −210 °C greatly increased the amount of ethylene recovered.The solid product is apparently transported to the cathode in the form of ions and may result from ionic polymerization of the acetylene. Acetylene is the volatile product formed closest to the cathode which suggests that it may also be formed by ionic processes. The formation of the remaining products is consistent with an excitation mechanism in which the C 2 products are formed first and the higher hydrocarbons are formed from them.