CHEMISTRY AND KINETICS OF CHEMICAL-VAPOR-DEPOSITION OF PYROCARBON - IV - PYROCARBON DEPOSITION FROM METHANE IN THE LOW-TEMPERATURE REGIME

Pyrocarbon deposition from methane was studied at ambient pressure and 1100 degrees C using a vertical hot-wall deposition reactor; the meth ane initial partial pressure was varied up to 75 kPa and the residence time up to 1 second. The influence of hydrogen partial pressure was s tudied at constant methane partial pressure. Steady-state pyrocarbon d eposition rates and corresponding compositions of the gas-phase were d etermined. Reaction models of homogeneous gas-phase and heterogeneous pyrocarbon deposition reactions were derived and used for simulation o f pyrocarbon deposition kinetics influenced by residence time, initial partial pressures of methane and hydrogen, and concentrations of acti ve sites. The importance of active sites and their blocking by hydroge n is discussed with special emphasis. (C) 1998 Elsevier Science Ltd. A ll rights reserved.