ABSTRACT In this work the production of glucose via hydrolysis of cellobiose using sulfonated active carbons as catalysts was studied. Commercial carbons presenting different types of porous system (micropores and mesopores) have been treated with sulfuric acid at different temperatures, being characterized afterwards. Such carbons have been tested as catalysts in the reaction of cellobiose hydrolysis. The results indicated that the type and density of sulfonic sites are not the only parameters responsible for the activity of the catalysts. Indeed, the porosity of the catalysts also plays an important role in the determination of the catalyst activity.

In order to produce gasoline directly from syngas, HZSM-5 can be added to the Fischer-Tropsch catalyst. However, this catalytic system shows an important deactivation rate. Aiming at describing this phenomenon, Fe-based catalysts and physical mixtures containing these catalysts and HZSM-5 were employed in this reaction. All these systems were characterized using the following techniques: XRD, XPS, TPR and TPD of CO. This work shows that HZSM-5 interacts with the Fe-based Fischer-Tropsch catalyst during the reduction step, decreasing the Fe concentration on the catalytic surface and thus lowering the activity of the catalytic system in the Fischer-Tropsch Synthesis.

This work aimed to determine the maximum content of cobalt that can be incorporated by ion exchange in zeolites H-USY, H-Beta, H-Mordenite, and H-ZSM-5. To reach this goal, batch isotherms at 75ºC were constructed after addition of zeolite samples in flasks filled with cobalt nitrate solution. The equilibrium data were fitted to Langmuir, Freundlich, and Tóth adsorption isotherm models. Langmuir was the best model for zeolites H-Beta, H-Mordenite, and H-ZSM-5, whereas experimental data for H-USY were better fitted to the Freundlich isotherm model. From the isotherms, it was possible to determine the maximum cobalt exchange level (q max) that can be incorporated in each zeolite through ion exchange. In this sense, H-USY presented the highest q max value (2.40 meq/g zeol), while H-ZSM-5 showed the lowest one (0.64 meq/g zeol). These results also show the influence of the zeolite framework related to the channel system, pore opening, presence of cavities and secondary porosity and SiO2/Al2O3 ratio (SAR) on the maximum capacity and behavior of cobalt ion exchange in protonic zeolites.

In this work the ion exchange isotherms of Cr3+, Mg2+, Ca2+ and K+ in single solutions and in binary mixtures (Cr/K, Cr/Ca, Cr/Mg) using NaX zeolite at 30ºC, 45ºC and 60ºC were reported. NaX isotherms were very favorable for all metal cations studied. The respective isotherms had some differences in shape, a consequence of competition for the exchange sites. The Kielland plots of all systems were non linear, which is a characteristic of sites of different energies involved in the exchange process. Temperature influenced the ion exchange as it could alter the hydration sphere of the in-going ions. Consequently, differences in thermodynamic properties and also in the selectivity were seen. It was concluded that NaX did not have a pronounced selectivity towards chromium.

The isopropanol decomposition reaction was used to evaluate the catalytic activity of ultrastable (USY) zeolites with different degrees of dealumination, treated in strongly alkaline medium at various temperatures and contact times. This treatment resulted in the reinsertion of non-framework aluminium, a result of the ultrastabilization process. The samples obtained were also submitted to an acid treatment, leaching the non-framework aluminium that had not been reinserted. The results obtained at 723K showed a large reduction in the acidic activity of the alkaline-treated zeolite, as the treatment conditions became more severe (the longer the treatment time or the higher the temperature, the higher the degree of dealumination). On the other hand, treated samples displayed some isopropanol dehydrogenation activity (basic sites). However, this activity was not very significant and did not depend on the alkaline treatment or ultrastabilization conditions used. The effect of reaction temperature and acid leaching on activity is also shown.