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.

The conversion of n-butane to iso-butene on gallium/HZSM-5 catalysts at 350ºC and WHSV=2.5h8-1 was studied. The catalysts were prepared by ion exchange from a Ga(NO3)2 solution and further submitted to calcination in air at 530ºC. TEM analysis with an EDAX detector and TPR-H2 data showed that after calcination the Ga species were present mainly as Ga2O3, which are reduced to Ga2O at temperatures near 610ºC. The specific acid activity (SAA) of the catalysts increased with the increase in aluminum content in the zeolite, and for a fixed Si/Al ratio, the SAA increased with Ga content. Values for specific hydro/dehydrogenation activity (SH/DHA) were significantly higher than those for SAA, indicating that the catalytic process is controlled by the kinetics on acid sites. Moreover, the production of iso-butene with a selectivity higher than 25% was a evidence that in gallium/HZSM-5-based catalysts the rate of the hydrogenation reaction is lower than that of the dehydrogenation reaction; this behavior confirmed the dehydrogenation nature of gallium species, thereby showing great promise for iso-butene production.

n-Heptane cracking on a USY commercial zeolite at 350, 400 and 450ºC was studied. XRF, XRD, 27Al and 29Si-MAS-NMR were used for USY characterization. The nature of the coke was determined by 1H-NMR and infrared spectroscopy. It was observed that temperature influenced the nature of the coke formed, and that an increase in temperature led to a reduction in the solubility of coke in CH2Cl2 and an increase in its aromaticity. Despite these characteristics and the larger amount of coke formed, higher temperatures have less effect on the deactivation process than lower temperatures. Selectivity for C1-C6 fractions was hardly influenced by temperature, and it was that expected for the cracking mechanism of n-paraffins on acid catalysts.