Cu and Fe species formed during the preparation of Cu/ and Fe/ZSM-5 catalysts by ion exchange were studied. XRD, SEM, H2-TPR, DRS-UV-VIS, EPR, Mössbauer Spectroscopy (MÖSS) and chemical analysis (AAS) were used to sample characterization. Cu/ZSM-5 catalysts, irrespective of their Si/Al ratio and Cu content, showed a reduction peak at around 210°C, which was attributed to the reduction of Cu+2 to Cu+1. The reduction peak of Cu+1 to Cu0 shifted to higher temperatures with the increase of Si/Al ratio or with the diminution of Cu/Al ratio, evidencing that isolated Cu cations present a higher interaction with the zeolite structure. The MÖSS data showed the presence of Fe+3 species in charge-compensation sites and a higher content of hematite (Fe2O3) in the catalysts prepared in aqueous medium. The EPR analysis also evidenced the Cu+2 and Fe+3 presence in Cu and Fe/ZSM-5 catalysts, respectively.
Cu/ZSM-5; Fe/ZSM-5; XRD; DRS-UV; H2-TPR; EPR; Mössbauer Spectroscopy
