Catalytic clean-up of gasification gas with precious metal catalysts – A novel catalytic reformer development

Several precious metal catalysts were prepared on modified zirconia and tested for the selective catalytic clean-up of the gasification gas. The activity of the precious metal catalysts were compared to that of the modified zirconia supported nickel catalyst and to the support. The activities of the catalysts were tested in a monolithic form in a quartz laboratory reactor at temperatures of 600–900 °C under atmospheric pressure using synthetic sulfur containing gas mixture. In addition, the stability of the Ni and Rh catalysts was examined by measuring the activities at 800 °C for 10 h using sulfur containing gas. The simulated gas contained CO, CO2, CH4, C2H4, H2, N2, H2O, H2S, NH3 and a tar model compound, i.e. a mixture of naphthalene and toluene. The addition of metal on the support promoted the activity in tar model compound decomposition only at the temperature range of 850–900 °C. The order of activity was Rh ≈ Ni > Pd > Ir > Ru > Pt. Almost complete tar model compound conversion was achieved with Rh, as well as with Ni, at 900 °C. At lower temperatures, the support showed higher activity in tar model compound decomposition compared to the metal/support catalysts tested. Only Ni and Ru showed moderate activity in ammonia decomposition. In regard to sulfur tolerance at 800 °C, Rh was activated during the 10 h experiment while the activity of Ni decreased. The performance of both was restored after the overnight N2 flush and the conversion of the tar model compound was higher for Rh (64%) than for Ni (46%).