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Ambient pressure hydro-deoxygenation (HDO) of the phenolic-rich pyrolysis liquid fraction is a complex task due to the presence multiple phenolic compounds and light oxygenates. The phenolic-rich fraction differs from the overall pyrolysis liquid, known to be prone to re-polymerization and coking in the reactor or of the catalyst. In the present research, hydro-deoxygenation of oxygen-containing compounds in the phenolic fraction over Mo-based catalysts was carried out for the first time. It was found that Mo-based catalysts can successfully upgrade the phenolics into aromatics, the conversion rate was nearly 100%. The small amount of light oxygenates in the phenolic-rich fraction had no obvious effect on the hydro-deoxygenation reaction, the phenolic conversion was more than 95%. After assessing the performance for a representative phenolic model compound, the reaction was also successfully carried out on the phenolic fraction of the real pyrolysis liquid. It can be concluded that the catalysts can also be used for the HDO of the real pyrolysis liquid fraction at atmospheric pressure., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The article discusses research investigating a mild hydrotreating process for biomass pyrolysis oils to produce a refinery feedstock suitable for use. According to the authors, fast pyrolysis produces a liquid product that is highly corrosive and immiscible with hydrocarbons despite its high percentage mass yield, which makes it unsuitable for use in a conventional petroleum refinery or as a finished fuel. The authors also note that catalytic hydroprocessing, which is an alternative that can remove oxygen to make a gasoline- or diesel-like product, is not cost effective. Topics include the results of an economic analysis that suggests mild hydroprocessing is economically viable and produces a product suitable for use in refinery processes.

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]