Efeito da substituição de ferro na hidroxiapatita sobre a conversão de etanol a produtos de maior valor agregado

Abstract

The evaluation of hydroxyapatite (Ca10-x(HPO4)x(PO4)6-x(OH)2-x) as a catalyst for the conversion of ethanol allows a wide investigation, because, due to its chemical nature, it is possible to modify its performance through strictly controlled changes in its physicalchemical properties. This work evaluates the effect of iron substitution on hydroxyapatite (Hap) on the ethanol conversion reaction. The catalysts nHap, 1% Fe-Hap, 5% Fe-Hap e 10% Fe-Hap were characterized by adsorption of N2 at 77K, X-ray diffraction using Rietveld refinement method, x-ray fluorescence, electron microscopy scanning, and thermo-programmed desorption of NH3. The reactivity of those catalysts was tested in the catalytic conversion of ethanol at different temperatures (350-450 °C) and GHSV of 24,000 ml g-1 h -1 . The results indicate that the replacement of Ca +2 ions by Fe+3 ions provided changes in the Ca/P molar ratio (1.54 - 1.14), specific surface (50-78 m2 /g), distribution of acid sites and total Hap acidity. The Rietveld method showed that iron ions occupied type I and II Ca sites, changing Hap’s lattice parameters. The insertion of the Fe+3 ion modified the catalytic conversion and product distribution, in which the 10% FeHap showed 73% conversion and selectivity for ethylene of 90% at 400 °C, when compared to 20% of conversion and 76% of ethylene for nHap.