Sticking probability of light hydrocarbons on tungsten

Abstract
Hydrocarbons were decomposed on the surface of an incandescent tungsten filament in a low pressure flow reactor. The rate of conversion of tungsten to ditungsten carbide W2C was measured by a resistance method. Carbon accumulation on the outer W2C surface was prevented by rapid inward diffusion. The sticking probability γ was defined as the probability that a room temperature hydrocarbon molecule striking the hot W2C surface would undergo complete decomposition to carbon and hydrogen. The value of γ for different hydrocarbons, measured over a 300-fold range of conversion rates, increased in the order: methane–3(methane only) to 2.6 × 10–2(methane plus hydrogen). This novel effect is explained by carbon patches on the W2C surface. These patches are associated with low values of γ but can be removed by adsorbed hydrogen.

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