1-Hexene Isomerization over Sulfated Mesoporous Ta Oxide: The Effects of Active Site and Confinement
Bibliographic record
Abstract
The isomerization of 1-hexene at 343 K was conducted over a series of sulfated mesoporous Ta oxides with pore sizes ranging from 12 to 30 Å. The results were compared to the popular industrial catalysts HY-zeolite, H-ZSM5, and Amberlyst 15. The conversion of 1-hexene to trans / cis -2-isomers can reach 95.89% in 4 h, which is roughly 2 times faster than Amberlyst 15 and 20 times faster than HY-zeolite and H-ZSM5. GC analysis confirmed that trans- and cis -2-hexene isomers formed through a double bond shift process as the only two principal products. The molar ratio of trans / cis -2-hexene isomers varies with pore size, clearly showing confinement effects in this process. The selectivity of our best material toward the trans -isomer is at least 3 times greater than that of either zeolite or Amberlyst 15. The best catalytic results in this study were achieved when using C 12 H 2 SO 4 mesoporous Ta oxide, which possesses a p K a of −8.2 and 19.8 mmol/g acid sites. The X-ray diffraction pattern showed complete retention of the mesostructure throughout catalysis as evidenced by a single broad reflection. Pyridine adsorption and infrared spectroscopy (IR) suggest that both Brønsted sites (∼1538 cm -1 ) and Lewis sites (∼1443 cm -1 ) coexist on the surface of these materials. The large amount of Brønsted acid sites, high BET surface areas, high acid strength Ho, and superior diffusion properties of C 12 H 2 SO 4 mesoporous Ta oxide are probably responsible for its extremely high catalytic activity and selectivity.
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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".