Thermal Decomposition of Gases and Liquids

Teresawa (49) studied the influence of operating variables, such as argon and methane flow rates and the dimensions of the RF torch, on the conversion of methane to acetylene. He observed that, under certain conditions, methane decomposed completely to 85% acetylene, when passed through the argon plasma. Teresawa also observed that the conversion to acetylene dropped and the level of reaction decreased 

Nishimura et cU. 41) studied the pyrolysis of propane in a 15-kW argon induction plasma. They fed in propane countercurrent to the tail of the argon plasma and found that the conversion of propane decreased with increasing distance between plasma and feed point. Nishimura et al. considered this phenomenon to be due simply to an effective decrease of the reaction temperature. Maximum yields of acetylene (28%) and ethylene (5%) were obtained at a feed distance of 2.5 cm. The yields of acetylene, ethylene, and carbon were found to decrease with increasing propane flow rates, which was considered to be caused by a decreased residence time of the propane in the reaction zone. 

Nishimura et al. also found that they could successfully inhibit carbon formation by adding hydrogen to the plasma argon. They were thus able to obtain a maximum yield of 40% acetylene while converting 

60% of the original propane. This yield, however, was achieved at an extremely high energy consumption of 780 kWh/m C2H2. 

A high surface-area carbon black (90 m /gm) was obtained by Jordan (32) by decomposition of butene-1 in an argon induction plasma. Butene-1 was injected into the plasma at a rate of 0.007 m /hr and after 1 hr operation 15 gm of carbon black was collected. A process for high surface-area carbon black (12) has also been developed in which a carbon feed is vaporized in an RF plasma and the vapor subsequently quenched in a halogen-rich environment. 

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