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Nickel (Ni) and ruthenium (Ru) decorated nanosprings (Ni-NS and Ru-NS) were prepared for use as potential hydrodeoxygenation (HDO) catalysts. The nanocatalysts were characterized by BET surface area measurements, electron microscopy and X-ray diffraction (XRD) and showed the NSs had a helical and mesoporous structure. The Ni and Ru decorated NSs showed good metal dispersity at the NS surface. Catalytic HDO conversion of phenol (model bio-oil compound) using NS were compared to conventional alumina (Al 2 O 3 ) and silica (SiO 2 ) gel catalyst supports. Ni–Al 2 O 3 was easily deactivated in the presence of water while the Ni-NS catalysts performed very well irrespective of water being present. An increase in Ni loading (up to 50%) increased the Ni-NS activity while the high loading resulted in a detrimental effect on the activity of silica gel based catalysts. Ru based catalysts showed better activity and conversion on phenol HDO than Ni based catalysts, even in the presence of water. Ponderosa pine pyrolysis bio-oil was fractionated into water-soluble (WS) and water-insoluble (WI) fractions. The bio-oil WI fraction was first hydrocracked to lower its molar mass and then HDO treated with Ni-NS to successfully form cycloalkanes products. These NS based HDO catalysts show promise for upgrading pyrolysis bio-oils to biofuels. [ABSTRACT FROM AUTHOR]

Fast pyrolysis converts >60 wt% of lignocellulosic materials into bio-oil. The two-step bio-oil hydrotreatment concept has had a major impact in the development of bio-oil hydro-treatment. In the first step, known as stabilization, the carbonyl and carboxyl functional groups are transformed into alcohols between 373 and 573 K, in the presence of noble metals (Pt, Ru and Pd) supported on carbon and metal oxides. In the second step, between 623 and 673 K, cracking and hydro-deoxygenation occur using Ru, Ni or sulfided CoMo catalysts. Transition metal phosphides and carbides are also active. The first section is devoted to summarizing the current understanding of bio-oil composition. The second section is an overview of bio-oil hydrotreatment processing parameters. Many of the bio-oil hydrotreatment studies in the literature are based on model compound results, which are reviewed in the third section. Section four is devoted to review studies with bio-oil fractions and the nature of polymerization and cross linked reactions responsible for catalyst deactivation. The progress in the development of new catalysts is discussed in section five. The review ends with a discussion on future prospects and challenges to hydrotreat pyrolysis bio-oils. • The two steps hydrotreatment concept had a major impact in the development of the field • Most common catalysts used in stabilization step: Pt, Ru and Pd • Most common catalysts for de-oxygenation: Ru, Ni and sulfided CoMo • Separation of bio-oil into fractions and separate processing is necessary • HDO of oligomeric fractions is challenging [ABSTRACT FROM AUTHOR]