Thermocatalytic synthesis of 2-butanol from biomass-derived levulinic acid using carbon-doped titania-supported ruthenium

Abstract

The thermocatalytic synthesis of 2-butanol (2-BuOH) from biomass-derived levulinic acid (LA) using carbon-doped titanium dioxide-supported ruthenium (denoted as Ru@C–TiO₂) was systematically investigated. The Ru@C–TiO₂ catalysts were synthesised via three different methods as follows: (i) a one-pot (op) approach from a solution of salt precursors at 150 °C for 24 h; (ii) coprecipitation–hydrothermal (cop) procedure from ruthenium solution and @C–TiO₂ at 150 °C for 24 h; and (iii) physical mixing (pm) of the precursors without solvent, followed by reduction with H₂ at 400 °C for 2 h. The catalysts were characterised by means of XRD, ATR-IR and Raman spectroscopies, TEM, N₂-adsorption, H₂-TPR, NH₃-TPD, pyridine adsorption, and UV-vis DRS techniques. XRD patterns revealed that (op)Ru@C–TiO₂ and (pm)Ru@C–TiO₂ comprised rutile phase TiO₂, whereas (cop)Ru@C–TiO₂ consisted of anatase phase TiO₂. The highest yields of 2-BuOH (87%) and 2-pentanol (2-PeOH) (11%) were achieved using the (op)Ru@C–TiO₂ (Ru = ∼5.0 wt%; C = 2.0 wt% to TiO₂) catalyst at 200 °C and at an initial H₂ pressure of 30 bar after 180 min. Furthermore, the (op)Ru@C–TiO₂ catalyst could be used for at least four reaction runs while maintaining the conversion of LA without any notable decrease in the yield of 2-BuOH.