Oligomerization of Fischer–Tropsch Tail Gas over H-ZSM-5
Bibliographic record
Abstract
Abstract Fischer–Tropsch synthesis produces a product that invariably contains C4 and lighter material. The C2–C4 fraction has a high olefin content. The light hydrocarbons in the Fischer–Tropsch tail gas can be separated from the unconverted synthesis gas, but the added cost and complexity of doing so by pressure distillation is often considered unjustified. In this study the possibility of reactive recovery of the C2–C4 olefins from the Fischer–Tropsch tail gas by oligomerization over H-ZSM-5 was investigated. Two specific issues were investigated for this unconventional application of this industrially practiced technology, namely, to determine the impact of low olefin partial pressure on productivity and to determine whether acid catalyzed CO reactions, such as the Koch reaction, were taking place. Catalyst and reactor system performance was evaluated using model propylene oligomerization. A catalyst productivity of 0.42 g·(gcat)−1·h–1 was achieved with a 39% C3H6 feed at 190 °C, 3 MPa, and weight hourly space velocity (WHSV) of 0.9 h–1. These results were comparable to previous reports in the literature. The same catalyst was employed to evaluate conversion of a model Fischer–Tropsch tail gas mixture containing 17.4% H2, 7.5% CO, 68.0% CH4, 0.65% C2H4, and 6.45% C3H6. The operating range 205–278 °C, 3 MPa, and WHSV 1–1.5 h–1 was investigated. At 237–278 °C and WHSV 1.5 h–1, catalyst productivity remained around 0.32–0.36 g·(gcat)−1·h–1. Despite an olefin partial pressure of only 0.22 MPa, better than 85% olefin conversion was achieved. The liquid product was olefinic and contained 70–80% naphtha and 20–30% distillate. No evidence was found that CO reacted with the olefins in the feed, either by the Koch reaction to produce carboxylic acids, or to form ketones. Deposits formed on the catalyst and deactivation was observed over a period of 240 h. The nature of the deposits varied from top to bottom in the packed bed. Analysis of the spent catalyst indicated that liquid filled pores preceded hydrogen transfer and aromatization to form coke-like deposits over time.
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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) | 0.002 | 0.001 |
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".