Valorization of Biomass‐derived Small Oxygenates: Kinetics, Mechanisms and Site Requirements of H₂‐involved Hydrogenation and Deoxygenation Pathways over Heterogeneous Catalysts

Abstract

Hydrodeoxygenation (HDO) is a key step in upgrading of biomass‐derived feedstocks to fuels and valuable chemicals. In this review, I select to discuss the current understanding of heterogeneous HDO catalysis of representative small oxygenates that are present in the bio‐crude obtained from thermochemical conversions of biomass raw materials, as the efficient valorization of these presently underutilized carbon sources would significantly improve carbon recovery and the overall process techno‐economics, in addition to facilitating downstream processing in some cases. A primary focus is laid on the kinetics, mechanisms and active site requirements of molecular H2‐involved hydrogenation and deoxygenation reactions of small aliphatic oxygenates. More often than not, surprising contrasts are found between gas‐solid and polar liquid‐solid interfaces and hint toward substantial restructuring and modifications of the catalytic surfaces and chemistries in polar liquids, particularly induced by protic molecules (the most abundant being water). Knowledge gaps, uncharted territories and associated challenges for the interrogations of these fundamental aspects are also discussed in this review.

Deoxydehydration of Biomass‐Derived Polyols Over Silver‐Modified Ceria‐Supported Rhenium Catalyst with Molecular Hydrogen

“…Therefore, utilization of biomass as an alternative source is highly desired [1–6] . In the field of biorefinery, removal of the oxygen atom in biomass is of great importance because of the higher oxygen content of biomass‐derived platform chemicals such as sugar derivatives than chemicals widely used in industry [7–15] . Deoxydehydration (DODH) reaction, which converts vicinal diols to olefins in one step, is a useful method for oxygen removal because of the regioselectivity for cis ‐vicinal diols and the versatility of product olefins [16–19] .…”

“…[1][2][3][4][5][6] In the field of biorefinery, removal of the oxygen atom in biomass is of great importance because of the higher oxygen content of biomass-derived platform chemicals such as sugar derivatives than chemicals widely used in industry. [7][8][9][10][11][12][13][14][15] Deoxydehydration (DODH) reaction, which converts vicinal diols to olefins in one step, is a useful method for oxygen removal because of the regioselectivity for cis-vicinal diols and the versatility of product olefins. [16][17][18][19] A typical DODH reaction is the production of 1,3-butadiene from erythritol, which is a C 4 sugar alcohol that can be produced from sugars or glycerol in large scale by fermentation.…”

Advances in Understanding the Selective Hydrogenolysis of Biomass Derivatives

“…Shi et al. critically reviewed mechanisms and site requirements of the hydrogenation and hydrodeoxygenation of small oxygenates with a primary focus on C 2 –C 4 oxygenates . Tomishige et al discussed the current understanding of metal oxide promoted metallic nanoparticles for hydrogenation and hydrogenolysis of polyols, acids, and furanics .…”

Tungsten–zirconia-supported rhenium catalyst combined with a deoxydehydration catalyst for the one-pot synthesis of 1,4-butanediol from 1,4-anhydroerythritol

“…Although biomassderived products are more sustainable and renewable, most of them are not convenient and economical as feedstocks for energy generation or the chemical industry due to the high oxygen content. [1][2][3][4][5] Catalytic conversions such as selective C-O hydrogenolysis (dissociation of the C-O bond and addition of hydrogen atoms from H 2 ) of biomass-based chemicals can effectively reduce the oxygen numbers and increase their commodity value. Sugar alcohols, such as glycerol, erythritol, xylitol, and sorbitol, are biomass-derived compounds widely used as sweeteners instead of sugar in the food industry.…”