tCalcium-hydroxyapatite catalysts loaded with different amounts of platinum Pt(x)/CaHAp were synthe-sized and characterized by N2-adsorption, X-ray diffraction, transmission electron microscopy, Fouriertransform infrared, ultraviolet-vis-NIR spectroscopy and temperature programmed reduction. It wasfound that the loaded platinum was mainly exchanged and dispersed on the apatite surface, formingparticles with an average size of 2 nm. The exchanged platinum, as shown by XRD, did not affect theapatite structure or its crystallinity. The specific surface area of the bare CaHAp as well as the mean porediameter, diminished by increasing the Pt loading, probably because the pores were partially blocked. ThePt(x)/CaHAp samples calcined at 500oC contained, beside the exchanged platinum, Pt and PtO. H2-TPRresults showed that the platinum occupied on the apatite at least two different sites.The acid-base and redox properties of the catalysts were studied using, as the probe reaction, butan-2-ol conversion. The impregnation of CaHAp with Pt decreased its natural basic properties and enhancedmarkedly the dehydrogenation of butan-2-ol into methyl ethyl ketone (MEK). In the presence of air,the production of MEK increased abruptly with the temperature. The reaction started at 30oC, passedthrough a maximum (90% of conversion) at 60oC and then it decreased rapidly. This important activityat low temperatures was attributed to Pt and Pt2+species associated with the basic Ca2+-O2-groups ofthe apatite.The synthesized bifunctional catalysts were also investigated in the acetone conversion, in one step,into methyl isobutyl ketone (MIBK). The optimal performance was achieved with the sample loadedwith 0.5 wt.% Pt. It displayed at 150oC and stationary state a MIBK yield of 23% with a selectivity of74%. Moreover, all the Pt(x)/CaHAp catalysts showed an acceptable stability over time on stream with noproduction of heavy compounds
Characterization and performance of the bifunctional platinum-loaded calcium-hydroxyapatite in the one-step synthesis of methyl isobutyl ketone
Leonarda F Liotta;
2013
Abstract
tCalcium-hydroxyapatite catalysts loaded with different amounts of platinum Pt(x)/CaHAp were synthe-sized and characterized by N2-adsorption, X-ray diffraction, transmission electron microscopy, Fouriertransform infrared, ultraviolet-vis-NIR spectroscopy and temperature programmed reduction. It wasfound that the loaded platinum was mainly exchanged and dispersed on the apatite surface, formingparticles with an average size of 2 nm. The exchanged platinum, as shown by XRD, did not affect theapatite structure or its crystallinity. The specific surface area of the bare CaHAp as well as the mean porediameter, diminished by increasing the Pt loading, probably because the pores were partially blocked. ThePt(x)/CaHAp samples calcined at 500oC contained, beside the exchanged platinum, Pt and PtO. H2-TPRresults showed that the platinum occupied on the apatite at least two different sites.The acid-base and redox properties of the catalysts were studied using, as the probe reaction, butan-2-ol conversion. The impregnation of CaHAp with Pt decreased its natural basic properties and enhancedmarkedly the dehydrogenation of butan-2-ol into methyl ethyl ketone (MEK). In the presence of air,the production of MEK increased abruptly with the temperature. The reaction started at 30oC, passedthrough a maximum (90% of conversion) at 60oC and then it decreased rapidly. This important activityat low temperatures was attributed to Pt and Pt2+species associated with the basic Ca2+-O2-groups ofthe apatite.The synthesized bifunctional catalysts were also investigated in the acetone conversion, in one step,into methyl isobutyl ketone (MIBK). The optimal performance was achieved with the sample loadedwith 0.5 wt.% Pt. It displayed at 150oC and stationary state a MIBK yield of 23% with a selectivity of74%. Moreover, all the Pt(x)/CaHAp catalysts showed an acceptable stability over time on stream with noproduction of heavy compoundsI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
