Modificações estruturais em sólidos lamelares para a obtenção de catalisadores contendo alumínio, titânio ou nióbio

Abstract

The layered solids Magadiite, Na-RUB-18, and potassium hexaniobate were hydrothermally synthesized and modified by many methodologies aiming isomorphous substitution and pillaring processes in order to generate potential catalysts. The materials were characterized by different techniques, namely, XRD, elemental analysis by ICP-OES and CHN, FTIR, NIR, DRUV-Vis, Raman spectroscopies, Solid-state MAS 29Si and 27Al NMR, N2 and CO2 physisorption, and FEG-SEM, EDS and TEM microscopies. Isomorphous substitutions with Al, Ti and Nb were carried out in the magadiite leading to various coordination sites. Also, some these procedures led to MOR and GIS topologies zeolite crystallization. For pillaring processes, the lamellar solids were previously swollen and verified that each one interacts differently with the intercalant agent. Magadiite was pillaring with pure silica and Al, Ti, and Nb mixed pillars, which present tetra-, penta-, and hexacoordination sites. It was found that to the processes involved metals the methods that promote a better homogenization and delayed the hydrolysis reactions tend to give more tetracoordinated Al and Ti sites, and pentacoordinated Nb sites. Na-RUB-18 was pillared with pure silica pillars and his textural properties were slightly different to the magadiite. Potassium hexaniobate was successfully submitted to silica pillaring giving a new porous double layered pillared material. To the obtained materials were suggested some catalytic reactions. The MAG-MOR series materials were applied on the glycerol dehydration, showing up to 80% of selectivity to acrolein. The layered niobates were applied on the CO2 cycloaddition to propylene oxide and display yields greater than 80% on the production of propylene carbonate. The materials resulting of the silicon and aluminum magadiite pillaring showed activity in cumene cracking, giving benzene and propene as reaction products.