Importance of Radical Desorption during the Catalytic Pyrolysis of Light Hydrocarbons
Pyrolysis/cracking of light hydrocarbons is an important class of reactions in the hydrocarbon processing industry. When a catalyst is used to intensify the reactions and to minimise the formation of by-products, the deactivation of the catalyst due to carbon formation is often the limiting factor for the industrial application of the catalyst system. When a conventional porous catalyst is used in the study of the pyrolysis of light hydrocarbons, the analysis of experimental data is often complicated because reactions take place both on the catalyst surface and in the gas phase (including pores). Our recent studies have indicated that the hydrocarbon radicals formed on the catalyst surface do not always continue their reactions on the catalyst surface. Instead, the radicals can desorb into the gas phase to initiate/participate in the gas-phase radical reactions when the mass transfer resistance for radical desorption is minimised. The desorption of radicals will help to minimise the formation of carbon on the catalyst surface. Therefore, the design of an industrial catalyst system must consider the chemical composition/structure of the catalyst as well as the physical/pore structure of the catalyst. In this paper, our experimental results showing the importance of radical desorption from a non-porous nickel mesh catalyst will be presented and discussed for the pyrolysis of ethane.