Analysis of the gas phase by in situ FTIR spectrometry and mass spectrometry during the CVD of pyrocarbon from propane

A Fourier transform IR spectrometer and a mass spectrometer have been coupled to a pyrocarbon low pressure CVD reactor in order to investigate the gas phase during pyrolysis of propane in the range 600-1060°C. The variations of the amounts of intermediate species such as ethylene, acetylene, and benzene are followed by infrared absorption measurements as a function of temperature and residence time. Mass spectrometry allows additional minor species to be identified. The overall study permits a reaction pathway from propane to diacetylene, benzene, and heavier species to be proposed.