Reforming of toluene with simulated automobile exhaust gas over hydrotalcite-like-compound-derived Ni catalyst

Abstract

Reforming of toluene, which is a model compound of gasoline, with model exhaust gas (model EGR gas) of gasoline engine was carried out with Ni catalyst. The Ni/Mg/Al catalyst prepared from hydrotalcite-like precursor compound showed higher performance than Ni/α-Al2O3 catalyst in terms of activity, stability and coke deposition resistance. The activity of Ni/Mg/Al after the initial deactivation was about 1/200 of Rh/CeO2 based on the weight of active metal (Ni or Rh), and the difference was much smaller than that of price between Ni and Rh. The amount of coke deposition on Ni/Mg/Al catalyst was increased with increases of W/F or partial pressure of toluene, especially at the outlet of the catalyst bed, where the coke formation is mainly due to CO disproportionation. The deactivation was also severer in larger partial pressure of toluene when the toluene feed was changed while partial pressure of H2O, N2 and CO2 was set constant to the model EGR gas. Large steady state H2 formation and high conversion were obtained at conditions with low partial pressure of toluene, similarly to the case of simple steam reforming, the Ni/Mg/Al catalyst after reaction can be regenerated by the combination of oxidation (at 773 K) and reduction (at 1073 K) treatments. The effect of feed ratio of H2O:N2:CO2 showed that low partial pressure of steam in model EGR gas in comparison with standard feed gas for steam reforming is the main reason for low toluene conversion and coke deposition resistance. On the other hand, the presence of CO2 did not affect the conversion and the coke deposition behavior so significantly.