Electrochemical routes for bio-liquids transformation
Thursday 12 May 2022 | 11:30 – 13:00 CEST
Chairs: Roman Tschentscher, Emma Fromant
- Presentation 1
Oxidative lignin depolymerization
Presenter: Sigi Waldvogel
- Presentation 2
Kolbe oxidation of acetic acid: challenges and opportunities for biomass upgrading
Presenter: Bastian Mei
- Presentation 3
Electrochemical hydrogenation of butanal and crotonaldehyde on copper surfaces
Presenter: Guido Mul
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Biomass conversion into chemicals, fuels and materials is seen as essential pillar of the future green society.
In combination with electricity production from renewable energy, this can lead to highly sustainable, CO2 neutral process configurations.
Electrochemistry enables the conversion of bio-based streams at mild conditions. This minimises degradation and enables the process integration of bio liquid production and upgrading at the feedstock source.
In this session recent developments within the H2020 project EBIO and the topically closely related H2020 projects LIBERATE and Selectively are presented. Based on lab scale studies new insights into the fundamental reaction mechanisms will be discussed during the first two presentations. The session will conclude with a presentation focussing on the design and operation of a pilot unit for electrochemical lignin conversion and product separation.
Biomass utilization as an energy carrier has been increasing rapidly in recent years. Besides heat or electricity generation, biomass can be utilized as a transport fuel or feedstock for the chemical industry. However, the complexity of biomass hampers its implementation. Raw bio-oil, produced via fast (fast-)pyrolysis, consists of a variety of organic compounds, with carboxylic acids being a major fraction (20- 30 wt%). Acids are specifically responsible for the low pH (<3) of the oil , leading to corrosion among others in gasoline or diesel engines of transportation vehicles. Clearly, (carboxylic) acids need to be removed.
Considering the expected surplus in electricity due to increasing capacities of solar and wind installations, electrochemical upgrading of bio-oil emerged as an appealing alternative for currently used energy intense upgrading technologies and Kolbe electrolysis including the Hoefer-Moest pathway is proposed as an electrochemical upgrading pathway to lower the acid content in bio-oil .
The EBIO project aims at revealing the full potential of (non-)Kolbe processes for conversion of carboxylic acids into hydrocarbons and alcohols via electrochemical oxidative. In this contributions, a detailed study on the pH-dependent coulombic efficiency, including discussion of the reaction mechanism based on in situ Surface Enhanced Raman Spectroscopy (SERS), will be presented and the general challenges associated with electrochemical upgrading of bio-oil will be discussed.
An essential step in the conversion and stabilization of biomass related (pyrolysis) oil is the selective conversion of oxygen containing molecules. To this end, typically catalytic hydrogenation reactions are performed in reactors operated at elevated temperatures and pressures (approx. 200 bar). Alternatively, oxygen containing molecules can be converted by electrochemical hydrogenation. In this study we discuss the electroreduction of saturated and unsaturated C4 aldehydes (butanal and crotonaldehyde) on polycrystalline copper electrodes. Using Raman spectroscopy, butanal was found to adsorb to the copper surface through bidentate binding, favoring 1-butanol formation with a remarkable Faradaic Efficiency (FE) of 93% at -0.8 V vs RHE (and -15 mA.cm-2) in 0.5 M butanol solution, relative to the formation of Hydrogen. The Copper surface is also effective for the electro-hydrogenation of Crotonaldehyde, showing 90% Faradaic Efficiency towards products of hydrogenation. Contrary to literature data, of the 90%, we observe ~75% towards the reduction of the aldehyde functionality, forming crotyl alcohol, and only ~15% efficiency towards hydrogenation of the C=C double bond, forming butanal. The specificity of the Cu surface towards reaction of croton aldehyde is so high, because of the very strong adsorption of crotonaldehyde on the Cu surface (through the C=C bond, as demonstrated by Raman spectroscopy), inhibiting adsorption of butanal. Our work shines light on the importance of the chemical nature of bio-oil components and their interaction with Cu electrode surfaces. In particular if the bio-oil contains (even small amounts of) compounds consisting of C=C bonds, these would inhibit the conversion of aliphatic aldehydes without conjugated functionality.
This event is free and open to all
Free access with Visitor Pass
Please note that this Programme may be subject to alteration and the Organisers reserve the right to do so without giving prior notice.