Mechanism and Kinetics of Ethanol–Acetaldehyde Conversion to 1,3-Butadiene over Isolated Lewis Acid La Sites in Silanol Nests in Dealuminated Beta Zeolite
Bibliographic record
Abstract
Biomass-derived ethanol (EtOH) and acetaldehyde (AcH) conversion to 1,3-butadiene (1,3-BD) is an alternative process for 1,3-BD production. The present investigation reports the preparation and characterization of isolated La sites introduced into the silanol nests in DeAlBEA as well as detailed studies of the mechanism and kinetics for the conversion of an EtOH–AcH mixture to 1,3-BD. La sites supported on DeAlBEA are found to be present as (≡SiO) 2 La–OH groups that are H-bonded with adjacent Si–OH groups, possessing high C–C coupling activity and stability, superior to state-of-the-art Y-DeAlBEA. La sites supported on silica (La-SiO 2 ) with a similar chemical structure but no H-bonding interaction with Si–OH groups were prepared for comparison. Lewis acid La sites promote AcH aldol condensation, and the activity of such sites is nearly identical for both La-DeAlBEA and La-SiO 2 . The rate of C 4 product formation increases by a factor of 4.8 upon addition of EtOH to the feed of AcH over La-DeAlBEA, whereas that over La/SiO 2 remains unchanged. Investigation of the mechanism and kinetics of AcH aldol condensation and EtOH–AcH conversion to 1,3-BD revealed two C–C bond forming pathways─AcH aldol condensation by Lewis acid La sites and direct coupling of EtOH–AcH over H-bonded (≡SiO) 2 La–OH···HO–Si≡ sites. This study provides important information about the role of the local environment of isolated Lewis acid sites and their effects on the direct coupling of EtOH and AcH to form 1,3-BD.
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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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".