Sulfur Promotion in Conjugated Isomerization of Safflower Oil over Bifunctional Structured Rh/SBA‐15 Catalysts
Bibliographic record
Abstract
Abstract The sulfur effect on conjugated linoleic acid isomer (CLA) formation during the combined hydrogenation/directed isomerization of safflower oil over a bifunctional (hydrogenation and isomerization) highly structured rhodium‐based catalyst (Rh/SBA‐15) was investigated either by direct addition of increased concentrations of 3‐mercapto‐1,2‐propanediol to the reaction medium or by doping Rh/SBA‐15 with the same sulfur‐based compound yielding the sulfur‐doped Rh‐catalyst (S–Rh/SBA‐15). These catalysts exhibited interesting activity, stability, and recyclability. The maximum CLA contents obtained during the combined reactions with 0, 0.2, 1, 2, 5, and 10 ppm sulfur additions were 73, 99, 131, 110, 105, and 68 mgCLA goil−1, respectively, whereas the amount of harmful trans monoenes remained below 8 %. The safflower oil after partially hydrogenation under the same conditions over S–Rh/SBA‐15 catalyst contained up to 110 mgCLA goil−1. These results showed clear evidence of the sulfur promotion effect on CLA formation during the dual hydrogenation/directed isomerization of safflower oil. A mechanism for the sulfur promotion of the heterogeneous catalyst Rh/SBA‐15 for the conjugated isomerization activity during hydrogenation/directed isomerization of safflower oil was determined by solid‐state 1H NMR analysis of the fresh and spent catalysts. This was also confirmed by liquid‐state 2H NMR analysis of deuterium‐labeled product aliquots withdrawn throughout the reaction. The sulfur promotion towards the double bond conjugation of linoleic acid to form CLA isomers could be explained mechanistically through the preferable formation of the more nucleophilic rhodium sulfide (RhSH) over that of the hydride (RhH). However, both types of Rh clusters constituted distinct catalytic sites leading to the formation of hydrogenation as well as conjugated and geometric isomerization products. The lumped kinetics model described the experimental data well and complied simply with the proposed mechanism.
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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) | 0.001 | 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".