This is my grab bag of things I’ve come across and found interesting while trying to research how a colony on the planet Venus would utilize the atmosphere. It is primarily made up of CO₂, so it is interesting to explore what kind of stuff you can make using CO₂ as a primary ingredient. After all plants are mostly made of CO₂ and H₂O.
Plastics Straight from CO₂
Novomer is a startup company which is making plastics out of CO₂. They also claim to be cost effective without subsidies.
But these guys DO require some fossil fuels. So it is not pure CO₂.
At Cornell they have managed to produce plastic without any fossil fuel but they require oil from orange peel.
Use Sabatier reaction as a stepping stone towards Plastic?
Sabatier units are simple to make according to Dr. Robert Zubrin, who demonstrated such a unit as part of working out his Mars Direct plan. These produce methane using hydrogen and carbon dioxide. Here is an example of a Sabatier reaction unit tested at the International Space Station.
Sabatier reactors are made primarily using steel pipes. The reaction is exotermic so it keeps going by itself.
CO₂ + 4 H₂ → CH₄ + 2 H₂O + energy
Illustration of the reverse reaction:
There is a company called Newlight which uses Methane (CH₄) for making plastic they call AirCarbon, which is a thermoplastic material.
Venus clouds contains sulphuric acid H₂SO₄ and hydrogen sulphide H₂S.
From space stackexchange:
A fun side benefit of Venus is that many major industrial processes (the Haber process, the Sabatier reaction, etc) require elevated temperatures and pressures for the thermodynamics to work out. On Venus, all that means is “descend”. :)
Getting Hydrogen and Oxygen
Hybrid sulfur cycle produces hydrogen and water and is supposed to be more efficient that regular water electrolysis.
H₂SO₄(aq) → H₂O(g) + SO₂(g) + ½ O₂(g) (thermochemical, T > 800 °C)
SO₂(aq) + 2 H₂O(l) → H₂SO₄(aq) + H₂(g) (electrochemical, T = 80-120 °C)
Net reaction: H₂O(l) → H₂(g) + ½ O₂(g)
This gets hydrogen and oxygen as result, which could again be used with Sabatier reaction to create Methane. This will leave us with water, methane and oxygen.
From Karen Rei at space stackexchange:
No, you don’t need to do electrolysis to extract oxygen from H2SO4 — you just have to heat it. H2SO4 breaks down at high temperatures to H2O+SO3, and the SO3 reduces to SO2 + O2. So you get both H2O and O2 from a simple process.
We could use a Solid Polymer Electrolyte to split water into oxygen and hydrogen. The water we get from reacting Sulfuric acid with hot graphite rods. Alternatively we can do:
2CO₂ → 2CO + O₂
Which happens when you heat CO₂ to 1100 degrees Celsius, when using a zirconia ceramic membrane.
A simpler way of doing it is using an iron-chrome or copper catalyst to produce water and Carbon monoxide
CO₂ + H₂ → CO + H₂O
This is endothermic but happens at 400 degrees which could be heat provided by a Sabatier reaction running next to it. Anyway heat should be the smallest problem to obtain on Venus, given that lead melts on the surface.
Make Graphite from Bosch reaction
Iron catalyst and 530–730 degrees Celsius, which shouldn’t be far from what you can get on Venus.
CO₂ + H₂ → CO + H₂O
CO + H₂ → C + H₂O
You can use graphite to make a crucible to hold molten metal. A crucible is a container that can hold things at high temperature. This is a big deal since we need deal with high temperatures for chemical reactions but will have limited access to metal on Venus.
University of Texas has looked into making methanol from CO₂. They use water rich in CO₂ with some fancy catalyst to produce methanol.
Making plastic and great fuel (Mars Direct)
The Mars Direct book has an interesting discussion of how to make plastic from CO₂ on page 467
This is the RWGS (water gas shift) reaction for making oxygen. Uses iron-chrome or copper catalyst. Simple steel pipe and some more needed.
H₂ + CO₂ → H₂O + CO
Iron based catalyst
2 CO + 4 H₂ → C₂H₄ 2 H₂O
Now we got ethylene, which is great fuel and key ingredient in making plastic. I discussed the process for making polyethylene plastic previously.
There are many benefits to making ethylene:
- Ethylene has just 2 hydrogen instead of 4 like methane. Saves on our hydrogen, but gives just as much fuel.
- Much easier to turn into liquid. Don’t need to be as cold and high pressure as methane. Cryogenics not needed.
- 50% less space. Less storage wasted.
- Basic ingredient for making polyethylene and polypropylene and many other plastics.
The space stack exchange discuss creating plastics specifically the ones which are resistant to the acid clouds:
Concerning plastics: there’s really no question that the perfect skin material is a PTFE copolymer with IR-reflective additives. PTFE is almost perfectly designed for the venus environment, in terms of its amazing chemical resistance, heat tolerance, UV stability, relatively simple production process, etc. It of course must be bonded with a ripstop. Normally on Earth we’d use nylon, but it’s really not ideal for Venus, the production chains are rather long. UHMWPE (spectra) is probably a much better choice; its monomer is easy to make, it’s incredibly high tensile strength (higher than Kevlar), very light (even floats in water), and very abrasion resistant. Also, both UHMWPE and PTFE, while neither of them like to adhere to anything, are both thermoplastics and can thus be thermally bonded.