Dechlorination of pentachlorophenol in supercritical carbon dioxide with a zero-valent silver–iron bimetallic mixture
Bibliographic record
Abstract
A continuous stream of pentachlorophenol (PCP, 10–20 mg min−1) in supercritical carbon dioxide (scCO2) was dechlorinated efficiently by a heated column (25 × 1 cm diameter) of a zero-valent silver–iron (Ag0/Fe0) bimetallic mixture. Dechlorination efficiencies in successive 10 min fractions of reactor eluate were influenced appreciably by the temperature and pressure within the reactor column(s), the flow rate of the mobile phase and especially by the composition of the feedstock solvent. During 1 h of operation at 450 °C, organically-bound chlorine was liberated, virtually quantitatively, from a 20% (w/v) feedstock stream (0.1 ml min−1 merged with 4 ml min−1 scCO2), and deposited as chloride ion on the surfaces of the metal particles. Sea sand, maintained under identical conditions, was capable of dechlorinating the substrate only partially (50% loss of the GC peak area for substrate; only partially dechlorinated products). By contrast, the dechlorination was virtually quantitative with the Ag0/Fe0 support. There was no evidence of PCP substrate or chlorinated aromatics among the products. In addition to approximately equal quantities of phenol and methylated phenols [o-and m-cresol; dimethyl- (2,4-, 2,6-, 3,4-, 3,5-, 3,5-dimethyl)phenol and trimethyl-(2,3,6-, 2,4,6-trimethyl)phenol] the remaining 5% of the product mixture consisted of methylated benzenes (m- and p-xylene, 1,2,4-trimethyl-, pentamethyl- and hexamethyl-benzene). If the feedstock solvent was changed from methanol to propan-2-ol, the product distribution was changed to ca. 50% phenol, 36% 1,2,4-trimethylbenzene and the remainder methylated phenols. In extended operation the reactor was run continuously for 14 h without apparent loss of activity provided that the chloride was washed from the Ag0/Fe0 metal surfaces at ca. 3 h intervals.
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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".