Hydrogenation of lignin-derived feedstocks and bio-oil using active and stable ruthenium catalyst

Abstract

Value addition of lignin-derived phenols into high-value chemicals and fuels is highly desirable and beneficial for bio-refineries owing to their broad applications in chemical and polymer industries. Here we present selective hydrogenation of various lignin-derived phenols into cyclohexanol and its derivatives using SiO2-Al2O3 supported stable and reusable Ru nanoparticles (Ru-NC/SiO2-Al2O3) in a green and sustainable manner. The Ru-NC/SiO2-Al2O3 nanocatalyst is prepared by simple impregnation followed by the pyrolysis method. The Ru-NC/SiO2-Al2O3 nanocatalyst shows excellent activity for the hydrogenation of lignin-derived functional phenols, including o, p, m-cresols, catechol, 4-n-propylphenol, diphenyl ether, guaiacol, eugenol, and others. In addition, hemicelluloses-derived furfural and furfuryl alcohol were also transformed into their hydrogenated products. Further, this transformation is also used for the hydrogenation of alkali lignin bio-oil, which is selectively transformed into corresponding cyclohexanol derivatives. HR-TEM, XPS, powder-XRD, N2 adsorption-desorption, and NH3-TPD analyses were used to examine the physicochemical properties of both fresh and spent Ru-NC/SiO2-Al2O3 nanocatalysts. Furthermore, the Ru-NC/SiO2-Al2O3 nanocatalyst is recycled and reused four times with no loss of any catalytic activity.