Coke characterization for an industrial Pt–Sn/γ-Al2O3 reforming catalyst

This work presents the characterization of carbon on deactivated Pt–Sn/Al2O3 industrial catalysts, with Pt–Sn (0.3–0.3 wt.%) and γ-Al2O3 (with 0.9 wt.% Cl). The samples were deactivated in different cycles of industrial operation and compared with a catalyst deactivated in methylcyclopentane (MCP) reaction under laboratory conditions. Different sets of samples were used: (a) PS0 (deactivation under laboratory conditions); (b) PS1, with one cycle of industrial operation; and (c) PS2, with 106 cycles of industrial operation. Deactivated catalysts were analyzed and characterized using a combination of different techniques: elemental analysis, atomic force microscopy (AFM), temperature-programmed oxidation (TPO) and 13C nuclear magnetic resonance spectroscopy for solids (NMR). The 13C-CP/MAS NMR spectra were very similar, indicating the presence of aromatic carbons. TPO profiles showed differences between the samples deactivated during industrial operation and that deactivated in the MCP reaction. In the case of industrial catalysts, one type of carbon was detected. In contrast, the catalyst deactivated under laboratory conditions showed two types of carbon or two types of adsorption sites. AFM images revealed two types of coke morphology, granulate and laminate, which were characterized at the nanometer scale. Our results show that the characteristics of the coke depend on the deactivation process, and that coke on the industrial catalyst could be successfully described and defined. However, to correlate all the data obtained from different techniques and to understand the complete mechanism of coke formation, more detailed analysis should be performed.