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Plastics from the sky
The ethane that sunlight makes in the upper air falls into the sea, and the plant turns it into plastic.
See it in the tour: chapter kraken shore, shot 4.2.
Ethane falls from the sky
Sunlight breaks methane in the upper air, and ethane is the main stable product left behind physics. It condenses and falls to the surface as a liquid, which is why the seas hold it physics. The full chain is in The orange sky. The settlers do not need to make carbon chains from scratch. The sky has already made the first link.
The barge carries ethane to the terminal with the methane, and the column separates it at 184.6 K physics. See Sorting the sea.
From ethane to ethylene
Plastic starts as ethylene, C₂H₄, which is ethane with a hydrogen molecule taken away:
C₂H₆ → C₂H₄ + H₂
It takes heat: 136.4 kJ per mole of ethane physics. Steam crackers on Earth run at 850 to 950 °C, and about 55% of the ethane becomes ethylene in one pass physics. The rest is separated and sent round again. The heat comes from the reactors design, and the hydrogen is a second product.
Ethylene boils at 169 K and ethane at 184.6 K, 15.6 K apart physics. That is a tighter gap than methane and ethane, so the column that parts them is taller design.
From ethylene to polyethylene
Ethylene molecules join end to end into long chains, and the chains are polyethylene. The catalysts that made it practical earned Ziegler and Natta the 1963 Nobel Prize in Chemistry physics. The reaction gives off heat, so the reactor sheds it into the same loop that warms the halls design.
The tour does not show a polymer plant, so the drawing is the picture.
What Titan makes and what comes in
Polyethylene is carbon and hydrogen and nothing else. Both are local. No oxygen is needed, and oxygen is the dear ingredient on Titan design. Plastics that contain oxygen, chlorine or sulfur have to pay for those atoms or import them design.
Catalysts, additives and the machines are imported through the Gateway as consumables and specialised machinery fiction. The economy imports high-value items and makes the bulk fiction.
Plastic in the cold
Polyethylene's glass transition is about 183 K, minus 90 °C, and published values run from about 150 to 250 K physics. Every one of them is above Titan's 94 K. A polyethylene part left outside is a glass. So the plastic goes where it is warm: film for the grow racks, pipe, insulation and the lining of tanks inside the shell design. See Building for 94 K and 1.5 bar.
Key numbers
| Quantity | Value | Basis |
|---|---|---|
| Cracking | C₂H₆ → C₂H₄ + H₂, 136.4 kJ per mole | physics |
| Steam cracker temperature / ethylene yield | 850 to 950 °C / about 55% | physics |
| Boiling point: ethylene / ethane | 169 K / 184.6 K | physics |
| Polyethylene glass transition | about 183 K (150 to 250 K published) | physics |
| Titan surface temperature | 93.65 K | physics |
| Catalysts and machines | imported | fiction |
Sources
- Horst 2017, Titan's atmosphere and climate, JGR Planets 122, 432
- Riley et al., Sandia National Laboratories SAND2021-11136J, steam cracking of ethane
- NIST Chemistry WebBook, ethane (enthalpy of formation, phase change data)
- NIST Chemistry WebBook, ethylene (enthalpy of formation, phase change data)
- Nobel Prize in Chemistry 1963, Karl Ziegler and Giulio Natta
- Open University, Introduction to polymers (glass transition of polyethylene)