Investigations of the identity of the true catalyst in three systems, including the development of catalyst poisoning methodology
Bibliographic record
Abstract
Following brief reviews of the pertinent "who is the catalyst?" and "M4 (M= transition-metal) cluster catalysis" literature, the research presented herein is focused on the investigations of the true catalyst for three different catalytic systems. The studies include: (i) the investigation of the true catalyst for neat benzene hydrogenation beginning with commercially available [Ir(cod)Cl]2 (cod= 1,5-cyclooctadiene) at 22 °C and 40 psig initial H2 pressure; (ii) the investigation of the true catalyst for benzene hydrogenation beginning with commercially available [RhCp*Cl2]2 (Cp*= pentamethylcyclopentadienyl) at 100 °C and 50 atm (740 psig) initial H2 pressure; and (iii) the investigation of the true catalyst for cyclohexene hydrogenation beginning with the well-characterized, site isolated [Ir(C2H4)2]/zeolite-Y complex at 22 °C and 40 psig initial H2 pressure, studies done collaboratively with Professor Bruce C. Gates and his group at the University of California-Davis. All three investigations aimed at identifying the true catalyst were studied via an arsenal of complimentary techniques including kinetics, in operando and post-catalysis X-ray absorption fine structure (XAFS) spectroscopy, kinetic quantitative poisoning experiments, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and high-angle annular dark-field scanning electron microscopy (HAADF-STEM). The data obtained for each system presented herein provide compelling evidence that the proposed species in each chapter are the true catalyst of the given system, specifically (and respectively) for (i), (ii), and (iii) above Ir(0)n nanoparticles and aggregates, Rh4 sub-nanometer clusters, and atomically dispersed, mononuclear Ir1/zeolite Y catalysts. The results emphasize the need to use complimentary, multiple methods in order to correctly identify the true catalyst in such catalytic systems. The final study elucidates kinetic quantitative catalyst poisoning via two model catalysts: Rh(0)n nanoparticles and Rh4 clusters, providing detailed analyses of linear as well as non-linear kinetic quantitative poisoning plots. The resulting quantitative kinetic catalyst poisoning studies of Rh(0)n nanoparticles and Rh4 clusters led to estimates of the equivalents of poison bound, quantitative catalyst poisoning association constants, and the numbers of active sites for each catalyst.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".