August 23, 2019, 11:51:09 AM
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Topic: Produce a low-freezing rocket fuel  (Read 19804 times)

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Offline Enthalpy

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Re: Produce a low-freezing rocket fuel
« Reply #45 on: April 15, 2019, 11:09:27 AM »
The usual process to separate H2 from CO, N2 and others after partial oxidation seems to be pressure swing adsorption (PSA). Looks simple and efficient. It can separate CO from N2 too, or maybe it's better to remove N2 from O2 prior to partial oxidation.

I've not found how quickly Ocotea caparrapi grows. Just "large tree (25m)" or "20m de altura". "Humid area surrounding the town of Caparrapi" suggests a fast growth under the equator.
https://es.wikipedia.org/wiki/Ocotea_caparrapi
https://www.academia.edu/15574491/Bandoni_LOS_RECURSOS_VEGETALES_AROM%C3%81TICOS_EN_LATINOAM%C3%89RICA_
https://pubs.acs.org/doi/pdf/10.1021/np960012r

Offline Enthalpy

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Re: Produce a low-freezing rocket fuel
« Reply #46 on: May 30, 2019, 06:44:56 PM »
Turpentine and other paper by-products make decent fuels, possibly separated as beta-pinene, alpha-pinene, carene, optionally saturated. But their big ring brings no or little heat of formation, loses two hydrogen atoms, and makes a stiffer molecule more prone to freeze. Due to C10, the flash point could be higher.

Maybe metathesis affords better molecules. Ethylene would make a C12, uneasily flammable. The flexible, open and very unsymmetric backbone should be harder to freeze. As is, it might be a (component of) jet fuel, or a Diesel fuel since the C3 chain eases autoignition. After saturation with hydrogen, it could be a rocket fuel, not magic but easily produced.

Beta-pinene, which has other uses, wouldn't fit as its double bond isn't in the ring. Carene I suppose neither because its big ring is unstrained. But alpha-pinene, otherwise little useful, has a double bond in its strained ring, which should help the metathesis.

The product has one very accessible double bond and may readily dimerize. I hope the strain in alpha-pinene lets the useful reaction outpace the unwanted one.

Comments please?
Marc Schaefer, aka Enthalpy

Offline Enthalpy

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Re: Produce a low-freezing rocket fuel
« Reply #47 on: June 02, 2019, 06:30:39 PM »
It goes without saying, but maybe better if I say it: longer alkenes can react with alpha-pinene to produce bigger molecules.

Symmetric alkenes like 2-butene would remain identical if reacting among themselves, but I suppose the double bond of alpha-pinene is too crowded for them.

Longer straight 1-alkenes (cheap propene, butene...) would increase the boiling and flash points of the product and ease its autoignition, while branched ones make autoignition harder if any useful. In a jet engine, a broader spectrum of boiling points stabilizes the flame, while in a Diesel engine, more uniform properties reduce sooting. This holds for metathesis products alone (synthetic fuels are a known solution to Diesel sooting), which can already be a mix, and holds also for mixes with biofuels or fossil fuels.

The longer metathesis products, having no fully exposed double bond, should be less prone to further metathesis.

Saturating the double bonds would improve the energy per mass unit of a jet fuel. If the alkene is obtained from methane of from C3 and C4 fractions, hydrogen is available.

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