Propane has been pyrolyzed in a flow reactor system at different temperatures ranging from 640° C to 1010° C and at 8 mbar of partial pressure which are typical vacuum carburizing conditions for steel. Nitrogen was used as a carrier gas. The products of pyrolysis were collected and analyzed by gas chromatography. The reactor was numerically simulated by 1D and 2D flow models coupled to a detailed gas phase reaction mechanism. The gas atmosphere composition has been predicted under the conditions of vacuum carburizing of steel. © 2007 Elsevier B.V. All rights reserved.