(95o) Selective Hydrogenation of Citral over Supported Pt Catalysts on Various Substrates
Highly dispersed platinum (Pt) nanoparticles (NPs) were deposited on various substrates by atomic layer deposition (ALD) for the reaction of citral hydrogenation. The substrates included multi-walled carbon nanotubes (MWCNTs), silica gel (SiO2), commercial Î³-Al2O3, and ALD-prepared porous Al2O3 particles (ALD-Al2O3). Based on TEM and CO-chemisorption analysis, the Pt NPs on all substrates were around 1.3 nm, and Pt/MWCNTs, Pt/ALD-Al2O3 and Pt/Î³-Al2O3 showed similar Pt dispersion (75%-85%). But the Pt dispersion on SiO2 was low (63%). In the reaction of citral hydrogenation, Pt/SiO2 showed the highest activity due to the strong acidity of SiO2 and the conversion of citral reached 82% after 12 hr with a selectivity of 58% of unsaturated alcohols (UA), including geraniol and nerol. Among all catalysts, Pt/MWCNTs showed the highest selectivity of UA (65%) due to its unique structure and electronic effect. In the cycling test, Pt/MWCNTs and Pt/ALD-Al2O3 catalysts were more stable than Pt/SiO2 which could be attributed to the different interactions between the catalysts and the solvent.