Enhancing bio-oil quality and energy recovery by atmospheric hydrodeoxygenation of wheat straw pyrolysis vapors using Pt and Mo-based catalysts

Andreas Eschenbacher, Alireza Saraeian, Brent H. Shanks, Peter Arendt Jensen, Chengxin Li, Jens Øllgaard Duus, Asger Baltzer Hansen, Uffe Vie Mentzel, Ulrik Birk Henriksen, Jesper Ahrenfeldt, Anker Degn Jensen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Atmospheric hydrodeoxygenation (HDO) of wheat straw fast pyrolysis vapors was studied as a promising route for the production of renewable liquid transportation fuels. The performance of TiO2-supported Pt (0.5 wt%) and MoO3 (10 wt%) catalysts was compared to an industrial Mo-based catalyst using a bench scale reactor operated at atmospheric pressure and up to high biomass-to-catalyst ratios (B:C). Mass and energy balances were complemented by detailed bio-oil characterization including advanced methods such as GC×GC-ToF/MS or -FID and 13C NMR. At 50 vol% H2, all three HDO catalysts effectively reduced the oxygen content of the bio-oils to ∼7–12 wt% (dry basis) compared to a non-catalytic reference (23 wt% O). MoO3/TiO2 was least efficient in conversion of acids (TAN = 28 mg per KOH), while Pt/TiO2 and MoO3/Al2O3 obtained oils with TAN ∼ 13 mg KOH/g (non-catalytic = 66 mg KOH/g). Compared to the TiO2-supported catalysts, the industrial Mo/Al2O3 catalyst produced higher yields of coke at the expense of condensed bio-oil. MoO3/TiO2 performed similar to Pt/TiO2 in terms of deoxygenation and energy recovery of condensed bio-oil, and by increasing the H2 concentration to 90 vol% the energy recovery of bio-oil increased to 39 and 42% at 8 and 10 wt% O (d.b.), respectively. Pt/TiO2 showed the highest selectivity to aliphatics and the lowest coke yields, e.g. the coke yield at B:C ∼ 8 was only 0.6 wt% of fed biomass. This study demonstrates that by using low-pressures of hydrogen and appropriate HDO catalysts, the quality of bio-oil can be improved without severely compromising its quantity (carbon yield) as observed under catalytic fast pyrolysis conditions.
Original languageEnglish
JournalSustainable Energy & Fuels
ISSN2398-4902
DOIs
Publication statusAccepted/In press - 2020

Cite this