Hydrodeoxygenation of lignin-derived bio-oil using molecular sieves supported metal catalysts: A critical review

It is an economical and environment-friendly method to produce renewable and sustainable oil by upgrading pyrolysis bio-oil containing phenolics. Among all upgrading methods, the hydrodeoxygenation (HDO)-based method of converting bio-oil into renewable fuels is one of the most promising and interesting technologies for the bio-oil refining, which can produce renewable fuels that have comparable quality to conventional fossil fuels. A high hydrogen pressure is usually required for HDO process when using the traditional hydrotreating catalysts. In recent years, molecular sieves supported noble metal and/or transition metal catalysts have been introduced in the reaction of lignin-derived bio-oil upgrading.. This paper summaries the HDO catalysts such as noble metal and transition metal catalysts that are supported on microporous molecular sieves, mesoporous molecular sieves and porous molecular sieves, as well as the HDO activities and the HDO reaction pathyways. The investigation of hydrodeoxygenation of phenolic model compounds in bio-oil over various metal(s)/molecular sieves is crucial to understand catalyst behavior for the hydrodeoxygenation process and to illuminate the reaction pathways of hydrodeoxygenation.