Aqueous-phase hydrodeoxygenation of sorbitol with Pt/SiO2–Al2O3: Identification of reaction intermediates

Aqueous-phase hydrodeoxygenation of sugar and sugar-derived molecules can be used to produce a range of alkanes and oxygenates. In this paper, we have identified the reaction intermediates and reaction chemistry for the aqueous-phase hydrodeoxygenation of sorbitol over a bifunctional catalyst (Pt/SiO2–Al2O3) that contains both metal (Pt) and acid (SiO2–Al2O3) sites. A wide variety of reactions occur in this process including CC bond cleavage, CO bond cleavage, and hydrogenation reactions. The key CC bond cleavage reactions include: retro-aldol condensation and decarbonylation, which both occur on metal catalytic sites. Dehydration is the key CO bond cleavage reaction and occurs on acid catalytic sites. Sorbitol initially undergoes dehydration and ring closure to produce cyclic C6 molecules or retro-aldol condensation reactions to produce primarily C3 polyols. Isosorbide is the major final product from sorbitol dehydration. Isosorbide then undergoes ring opening hydrogenation reactions and a dehydration/hydrogenation step to form 1,2,6-hexanetriol. The hexanetriol is then converted into hexanol and hexane by dehydration/hydrogenation. Smaller oxygenates are produced by CC bond cleavage. These smaller oxygenates undergo dehydration/hydrogenation reactions to produce alkanes from C1–C5. The results from this paper suggest that hydrodeoxygenation chemistry can be tuned to make a wide variety of products from biomass-derived oxygenates.

Reaction chemistry for the aqueous phase hydrodeoxygenation (APHDO) of sorbitol was studied over Pt/SiO2–Al2O3 catalyst at 518 K and 2.93 MPa.Figure optionsDownload high-quality image (69 K)Download as PowerPoint slide