Characterization of Cu species on SiO2 and ZSM-5 by temperature-programmed reduction by ammonia

We studied the temperature-programmed reduction by NH3 (NH3-TPR) as a supplement to the temperature-programmed reduction by H2 (H2-TPR) for the characterization of supported Cu species. The NH3-TPR profile of Cu/SiO2, which contained only bulk CuO, exhibited two peaks for N2 formation in equal amounts, suggesting stepwise reduction of the bulk CuO. In contrast, the H2-TPR profile exhibited only one H2 consumption peak. We also studied Cu-NaZSM-5 samples with various Cu and Na loadings. The Cu ions on ZSM-5 were reduced to Cu+ but no further. Kinetic analysis revealed that the NH3-TPR profile exhibited peaks for separate reductions of isolated and binuclear Cu2+ ions. Thus, we found NH3-TPR to be useful for detailed analysis of the reducibility of Cu2+ to Cu+ in zeolite pores.