Abstract: The effects of Mg addition on the catalytic performance of PtNa/Sn-ZSM-5 in propane dehydrogenation was investigated using catalytic reaction performance tests and physicochemical characterizations such as X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), NH₃ temperature-programmed desorption (NH₃-TPD), H₂ temperature-programmed reduction (H₂-TPR), and O₂ temperature-programmed oxidation (O₂-TPO). It was found that addition of appropriate amounts of Mg (0.3% and 0.5%, mass fraction) promoted the dispersion of metallic particles and decreased carbon deposition. In these cases, the presence of Mg in the PtMgNa/Sn-ZSM-5 catalyst could inhibit reduction of Sn species, thus more Sn could exist in oxidized states, which is advantageous to the reaction. However, when the content of Mg was excessive, the metallic particles were not well distributed and the particles agglomerated more easily. Moreover, the reduction of Sn species at high temperatures is relatively easy, which is disadvantageous to the reaction. In our experiments, the addition of 0.5% Mg to the PtNa/Sn-ZSM-5 catalyst gave the best catalytic performance. After reaction for 7 h, higher than 95% selectivity toward propene was achieved with a corresponding propane conversion value of 38.7%.

Key words: Mg, Sn-ZSM-5, Propane dehydrogenation, Catalytic performance, Catalyst