Vapor phase hydrogenation of aqueous levulinic acid over hydroxyapatite supported metal (M = Pd, Pt, Ru, Cu, Ni) catalysts.

Ca-5(PO4)(3)(OH) (HAP) supported metal (Ru, Pt, Pd, Cu and Ni) catalysts were examined for vapour phase hydrogenation of aqueous levulinic acid (LA). Ru/HAP demonstrated higher TOF of gamma-valerolactone (gVL) over the other metal catalysts. The LA dehydration products such as angelica lactones (both alpha- and beta-AL) were formed significantly over Pt, Pd, Ni and Cu/HAP catalysts. Influence of Bronsted and Lewis acid sites was exemplified by pyridine adsorbed FT-IR studies on Ru/HAP that exhibited very weak band due to Bronsted sites at 1552 cm(-1) and a strong band at 1450 cm(-1) attributed to Lewis acid sites. Ru supported on SO42--HAP demonstrated selective dehydration of LA to alpha-angelica lactone. Hydrogenation activity of Ru was diminished while supported on SO42--HAP, quite contrast to this the fresh HAP behaved as a selective support for Ru towards GVL formation. Thus, HAP has been identified as suitable support for Ru in the conversion of LA at ambient pressure. (C) 2015 Elsevier B.V. All rights reserved.