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Produce a low-freezing rocket fuel

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Enthalpy:
Hello nice people!

As a rocket fuel operating on Mars, a chilly world, I consider branched alkanes freezing around -100°C, but with some 15 carbons so the flash point is safely above terrestrial temperature. 2,4,6-trimethyl-dodecane would be one such compound, but isn't available in tons nor easy to mass-produce.

(a) Do you agree?

My hope is to replace each side methyl at the previous compound by two geminal methyl groups (drawing), and shorten the alkyl tail a bit. This improves often the liquid range, and I imagine the compound could be produced by acid-catalysed alkylation, like isooctane is produced in oil refineries.
That is:
Isobutane and Isobutene give Isooctane (2,2,4-trimethyl-pentane)
Isooctane and Isobutene give 2,2,4,4,6-pentamethyl-heptane
pentamethyl-heptane and 1-Butene give 2,2,4,4,6,6-hexamethyl-decane

(b) What do you think?

In fact, I consider one could buy from a refinery the Isooctane, and even 2,2,4,4,6-pentamethyl-heptane, which must be a by-product contained in the refinery's alkylation output. Or buy the complete alkylate and separate the pentamethyl-heptane by distillation.

(c) Does this look sensible?

(d) In case 100t are needed, would a refinery de-tune briefly its alky unit to increase the C12 proportion?

So the rocket fuel would only need to append the straight alkyl tail to the C12 alkylate (this tail is to lower the melting point and the autoignition temperature).

(e) Feasible? Will the new bond target the only tertiary carbon?

(f) to (z) plus all the greek alphabet: other comments, flames, rants if needed.

Thank you!

Enthalpy:
Other broad liquid range compounds depicted below are Pristane, or 2,6,10,14-tetramethyl-pentadecane (induces autoimmune diseases in mice) and Phytane (one CH2 longer, no such reputation). They seem to be scarce in Nature and difficult to mass-produce, making them lab rarities.

(f) Do you agree?

As above, I imagine geminal methyl groups would keep a broad liquid range and enable massive synthesis by acid-catalysed alkylation, this time using Isohexene (4-methyl-1-pentene), in the hope that the new bond forms at the alkane's only tertiary carbon.

(g) Does this make sense?

Thanks!

Enthalpy:
(c) and (d) Meanwhile I've found more realistic literature about alkylation in refineries (terra incognita for me, sorry) and it differs from the only reaction given in encyclopaedia...

Refineries feed not just isobutene but as well propene, 1-butene, 2-butene, some pentenes... The alkylate may contain 28% of 2,2,4-trimethyl-pentane, and 16% of each 2,3,3- and 2,3,4-, plus a broad mix.

As the sought ultralow freezing point is very sensitive to the methyl groups location, the Martian rocket fuel would need more controlled synthesis conditions than a refinery - or a careful separation of the 2,2,4-trimethyl from the refinery alkylate.

More, refinery alkylate lacks iso-C12. I suppose C8 products leave the reaction zone quickly as they appear and condensate. Producing heavier isoparaffins would need a separate reactor in liquid phase or warmer.

Is that correct?

fledarmus:
Pure iso-octane (2,2,4-trimethylpentane) is readily available. It is used as the standard for octane number in gasoline engines.

Honclbrif:
Why not use a mixture of materials and let colligative properties do the heavy lifting?

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