Experimental study on the formation of higher fluorocarbons from CF4 by a tip–tip electrical arc discharge at very high pressure

This work presents the study of the synthesis of higher fluorocarbons from tetrafluoromethane (CF4) with a plasma process based on the generation of a tip–tip electrical discharge at very high pressure. A series of experiments were performed using a He/CF4 mixture with a ratio 60/40% at a pressure of 2 MPa to investigate the effects of two modes of treatment: a continuous mode and an intermittent mode including a 30 s relaxation time between two successive discharges. The study shows the production of low quantities of saturated fluorocarbons (C2F6 and C3F8) at the experimental conditions employed. It also shows the intermittent mode of treatment to be more efficient in the synthesis of the saturated C2 and C3 fluorocarbon molecules in comparison to the continuous mode. The continuous treatment mode leads to unfavorable kinetics of synthesis for a given discharge duration while the intermittent treatment mode leads to an increase of higher fluorocarbon production with the number of discharges.