Deactivation Studies of Alkali-Promoted Trimetallic Co−Rh−Mo Sulfide Catalysts for Higher Alcohols Synthesis from Synthesis Gas
Bibliographic record
Abstract
Multiwalled carbon nanotubes (MWCNTs) and activated carbon (AC)-supported K (9 wt %)-promoted trimetallic Co (4.5 wt %)−Rh (1.5 wt %)−Mo(15 wt %) catalysts are used to study the long-term deactivation for continuous 720 h of higher alcohols synthesis (HAS). The fresh catalysts are extensively characterized in both oxide and sulfide phases, together with the spent catalysts. The catalysts are tested for the synthesis of higher alcohols from synthesis gas under similar conditions of 330 °C, 9.1 MPa (1320 psig), and 3.8 m 3 (STP)/((kg of cat.)/h), using a H 2:CO molar ratio of 1.25. The alkali-promoted trimetallic Co−Rh−Mo catalyst supported on MWCNTs has shown two different deactivation steps: loss of sulfur from the surface and sintering of the catalyst species located on the outer surfaces of the carbon nanotubes. After regeneration, the total activity recovery (∼10%) over this catalyst is close to the total activity loss during the first deactivation step. The percentage CO conversion decreased from 58% to 51% and from 43% to 30% over the catalysts supported on MWCNTs and AC, respectively, over 720 h of time-on-stream; indicating a loss of activity of 12% and 30% over the catalysts supported on MWCNT and AC, respectively. Characterizations of the spent catalyst supported on activated carbon revealed that deactivation occurs because of the sintering of metal sulfides, which causes low metal dispersions and high pore blockage of the support. The total hydrocarbon formation decreased rapidly during the first deactivation step and then slowly leveled off. The initial decrease in the total hydrocarbons space time yield (STY) may be explained from the loss of sulfur from unstable metal sulfide crystallites on the surface of the catalyst to the products and sintering of the catalyst species is responsible for the later steps. The total alcohols STY of 0.281 and 0.202 g/(g of cat./h) are observed during the reaction period of 24 h over the catalysts supported on MWCNTs and activated carbon, respectively. The sulfided MWCNT-supported catalyst suffers a 1% decrease while the AC-supported catalysts exhibits a 4% decrease in normalized higher alcohols yield between 24 and 720 h on-stream.
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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 | 0.001 | 0.003 |
| 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 | 0.000 | 0.001 |
| Open science | 0.001 | 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 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".