In situ characterization of silicon micro channel reactor with supported platinum alumina catalyst prepared on the channel wall was conducted with FT-IR microscope under propane flow, propene flow and cyclohexane flow. Surface pi-allylic species along with surface OH group were observed at 373 K under propane or propene flow. These species were rather stable under N-2 flow and H-2 flow. The reactor was active for dehydrogenation of cyclohexane to produce benzene and cyclohexene. In situ FT-IR observation under flow of cyclohexane at 473 K. decrease of reactant, increase of products, a maximum of pi-allylic and C=C species were observed from inlet toward outlet. The maximum absorbance of the intermediate shifted with flow rate. These suggested consecutive reaction path and existence of film resistance. (C) 2010 Elsevier By. All rights reserved.