Characterization of coke deposited on Pt/alumina catalyst during reforming of liquid hydrocarbons

Temperature-programmed oxidation (TPO), Raman spectrometry, and X-ray photoelectron spectroscopy (XPS) are used to characterize coke species deposited on a 0.61 wt% Pt/alumina catalyst for three reactions, carried out separately: partial oxidation (POX), steam reforming (SR), and autothermal reforming (ATR). Three individual compounds were used as simulants of liquid fuels in each of these three reactions: tetradecane, decalin, and 1-methylnaphthalene. The TPO profiles of the coke showed that partial oxidation and steam reforming resulted in generally greater coke deposition than autothermal reforming for each of the fuels. 1-Methylnaphthalene produces more coke than the other fuels in each of the reactions. Coke appears to be deposited both on the metal and the support, with the coke on the metal being more easily oxidized by TPO. Raman spectroscopy shows that there is no significant change in the carbon crystallite size on any of the catalysts; all are within the range of 1.45–1.83 nm. XPS analysis of carbon deposited during partial oxidation of tetradecane shows that small amounts of graphitic carbon (C/Al ratio < 0.10) remain even after treatment in oxygen for 15 min at 600 °C.