Abstract: The alumina-supported noble metal iridium catalysts were prepared by the impregnation method. The effect of additive ZrO2, La2O3, or MgO on the catalytic performance was investigated. The supported catalysts were used for the methanol decomposition reaction and were characterized by X-ray photoelectron spectroscopy, temperature-programmed reduction (TPR), temperature-programmed desorption of hydrogen (H2-TPD), and temperature-programmed desorption of carbon monoxide. The promoter addition could remarkably improve the hydrogen selectivity and CO selectivity of Ir/Al2O3 catalyst in the methanol decomposition. La2O3 and ZrO2 were also good promoters for enhancing the methanol conversion. Both hydrogen and CO were held strongly by the MgO-modified Ir/Al2O3 catalyst, which was not favorable for the methanol conversion. The results of TPR and H2-TPD showed that hydrogen spillover existed in the alumina-supported iridium catalyst. The addition of one of the three promoters could significantly enhance the hydrogen spillover effect.

Key words: iridium, alumina, supported catalyst, zirconia, lanthana, magnesia, promoter, methanol decomposition