Coke formation on an industrial reforming Pt-Sn/γ-Al₂O₃ catalyst

The characterization of the coke deposited on an industrial Pt-Sn/γ-Al₂O₃ catalyst, used in a continuous reforming process, was performed with AFM, XRD, FTIR, EPR, NMR, TG-DTG and DTA techniques. Composition, structure and location of the coke on the catalyst were investigated. The coke was predominantly deposited on the catalyst surface and in the interstices between the catalyst particles. Its content increased along the reactor from top to bottom. Coke was deposited in the form of uniform films and clusters of three-dimensional disks with diameters between 0.12 and 0.18 μm. It had a pseudo-graphite structure produced by the dehydrogenation and polymerization of the aromatic precursor compounds. The coked catalyst showed a good combustion behavior; it was regenerated below 550°C. These results are important to elucidate the coke formation mechanism, to generate new continuous reforming catalysts, and to optimize the reactor operation parameters.