Electrocatalytic Upgrading of Biomass Fast Pyrolysis Oil
Bibliographic record
Abstract
Attempts to electrocatalytically upgrade bio-oil have been made in recent years. Mostly, the ECH (Electrocatalytic Hydrogenation) experiments of bio-oil were done using fixed bed electrode configurations at room temperatures and low current densities (<100 cm-2). The main goal was to demonstrate the viability of ECH as a bio-oil stabilization strategy, mainly through reduction of carbonyl contents (aldehydes and ketones) which could cause polymerization. High temperature may promote condensation polymerization of fast pyrolysis oil, low-temperature ECH is therefore considered a promising approach to stabilize pyrolysis oil. However, recent advances in ECH of fast pyrolysis oil have shown the limited reductive upgrading chemistry (hydrogenation, hydrogenolysis, or hydrodeoxygenation) through this approach. This was mainly attributed to the complexity of fast pyrolysis oil and the restricted electrolysis operating conditions. Most of the published works in ECH of pyrolysis oil reported the reduction of carbonyl content into alcohols in the substrate rather than the hydrodeoxygenation of aromatics or phenolics. In this study, ECH of fast pyrolysis oil (FPO) in acidic electrolytes using SSER (Stirred Slurry Electrocatalytic Reactor) configuration was conducted for the first time. A compositional analysis suggested that the FPO sample contained water (29 wt.%) and detected monomers (38.5 wt.%), which comprise of carbohydrate derivatives (35.2 wt.%) and lignin derivatives (3.3 wt.%). Balance of water and monomers must be oligomers. Three polar organic solvents (e.g., ethanol, isopropanol, and acetone) were tested in a mixed aqueous and organic electrolyte with MSA solution. The electrolysis experiments were carried out for 4–30 h at constant cathodic current densities (I = -218 to -255 mA cm-2) and temperatures (50–60 oC). In all cases, decreases in the weight average molecular weight (Mw) and the number average molecular weight (Mn) were observed with prolonged reaction times. Temperature and catalyst loading contributed to faster depolymerization of the oligomers. Using different organic solvents (e.g., ethanol, isopropanol, acetone), the degree of depolymerization was about 33–37% after nearly 20 h reactions. Color changes in the catholyte FPO samples were observed in all cases after 18–25 h, turning from dark brown to light yellow. This observation supports the GPC results showing the molecular weight reduction after the ECH. In this study, compound distributions were determined based on ten functional groups, such as acids, alcohols, aldehydes, ketones, esters, furans, alkanes, aromatics, phenols, and guaiacols. In all cases, the reduction of ketones, aromatics, and guaiacols was noticed, while the alkanes content slightly increased. The most dramatic increases in esters content were observed when ethanol (17–25%) or isopropanol (19–32%) was used. This was attributed to esterification of carboxylic acids (mainly acetic acid) in the FPO with alcohols in the presence of MSA, which catalyzed the reaction. Reduction of p-eugenol to cerulignol (4-propylguaiacol) was the most noticeable in all cases, implying that the unsaturated bond in the allyl group is easily reduced under the ECH conditions. Significant increases in the cerulignol contents were achieved with all the different solvents: ethanol (0.5–4.9%), isopropanol (1.4–6.9%), and acetone (1.4–5.4%), based on the composition calculation normalized by the lignin-relevant compounds detected in the catholyte samples. ECH of FPO in SSER with organic solvents addition has demonstrated mild depolymerization of FPO oligomers, esterification, and reduction of carbohydrate and lignin derivative monomers which could potentially upgrade the quality of FPO for synthesis of hydrocarbon fuels.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".