Deactivation Behavior of Carbon Nanotubes Supported Cobalt Catalysts in Fischer-Tropsch Synthesis
Bibliographic record
Abstract
ABSTRACT: The effects of electronic properties of inner and outer surfaces of Carbon Nano Tubes (CNTs) on the deactivation of cobalt Fischer-Tropsch (FT) catalysts were studied. The comparative characterization of the fresh and used catalysts by TEM, XRD, TPR, BET and H2 chemisorption showed that cobalt re-oxidation, cobalt-support interactions and sintering are the main sources of catalyst deactivation. TEM showed that 480 h continuous FT synthesis increased the average particles size of the particles located inside the pores from 7 to 7.4 nm while the average particles size of the particles located outside of the tubes increased from 11.5 to 25 nm. XRD analysis of the used catalyst confirmed cobalt re-oxidation and interaction between cobalt and CNTs and creation of carbide phases. When the %Co conversion and H2O partial pressure in the reactor are high, the deactivation rate is not dependent on the number of the catalyst active sites and is zero order to %CO conversion. In this case the main deactivation mechanisms are cobalt re-oxidation and metal support interactions. At lower amounts of the %Co conversion and H2O partial pressure, deactivation can be simulated with power law expressions with power orders of 11.4 for the particles outside the tubes and 30.2 for the particles inside the tubes and the main deactivation mechanism is sintering. Due to the electron deficiency of the inner sides of the CNTs, the interaction between the cobalt oxides and the support is stronger leading to lower rates of sintering as compared with the particles located on the outer layers of the CNTs. Regeneration recovered the catalyst activity by 54.3 % of the total activity loss.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| 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) | 0.000 | 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 teacher head, 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".