[Enthalpy]

The photosynthetic path is inspired by known photoaddition processes, for instance
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0528
and despite having no experience for it, I dared to adapt the idea, so please take my proposal with all due caution.

Photoaddition is praised to avoid cyclodimers, like cyclooctadiene from butadiene. Further, to let reactants add with one of a different kind, I imagine to excite only one reactant through wavelength selectivity, and have the excited reactant less concentrated so it combines more probably with a different reactant, instead of dimerizing.

Excimer lamps exist with proper wavelengths. See for instance Iupac, Heraeus or others:
http://old.iupac.org/goldbook/ET07372.pdf
http://www.heraeus-noblelight.com/en/products_1/uvprozesstechnik_1/uvp_excimer.aspx
- Xe2 radiates at 172nm, 900W consumption, perfect for ethylene;
- KrCl at 222nm, 3000W consumption, fits 1,3-butadiene around 217nm;
- KrI 190nm, ArF 193nm and others are not catalogue parts.
Xe2 is said to offer up to 40% efficiency, good others 5 to 15%.

I plan no sensitizer, since the lamps have the proper wavelength. This shall hopefully improve the light efficiency; the excimer lamps would then consume less electricity than 50k€/t used by the 7% efficient mercury lamp in the above cited photoaddition, which has 1/26 quantum efficiency. Stirring and permanent reactant feed shall improve also. Would a sensitizer improve or degrade the reaction selectivity? No idea. Maybe a wrong choice, or not.

Solvents widen too much the absorption wavelength peak, so gases shall react. With light absorption of 15000/cm and 21000/cm for ethylene and butadiene in molar solution, 1mb of reactants would already absorb within 1cm, so stir if using a higher partial pressure. The reactants can hence be cold, nice against spontaneous polymerisation and leaks; operating near their (reduced pressure's) boiling point would let the products condense away as they form. To widen absorption peaks by 2*5nm and fit the lamps, add about 10b of a nonreactive gas (nitrogen? Rare gas?) which must be pure for transparency. Mind absorption throughout light path!

----- To vinyl-cyclobutane

Excited butadiene reacts mainly with the more abundent ethylene to make vinyl-cyclobutane; proportions can keep some divinyl-cyclobutane.

Alternately, excited ethylene reacts mainly with the more abundent vinyl-cyclobutane. This would produce more cyclobutane, which shall be controlled in a rocket fuel as it's volatile, so distill. Products separation within the reactor also gets less obvious.

----- To cyclobutyl-cyclobutane (Boctane)

Excited vinyl-cyclobutane (by KrI, ArF lamp?) reacts mainly with the more abundent ethylene to make cyclobutyl-cyclobutane (Boctane).

Alternately, excited ethylene reacts mainly with the more abundent vinyl-cyclobutane. This would produce more cyclobutane.

The 1,2-trans-divinyl-cyclobutane fraction makes dicyclobutyl-cyclobutane, which is denser than Boctane, less flammable, and could well improve the melting point, so keep it in Boctane! Adjust its proportion through the gas partial pressures in the first cycloaddition.

Photo dimerization of vinyl-cyclobutane will also provide some dicyclobutyl-cyclobutane, possibly the 1,3 isomer whose mix should lower the melting point, welcome. Tune the gas partial pressures in the second cycloaddition.

----- Variants

I wish C=CC=C butadiene is replaced by piperylene C=CC=CC, isoprene C=C(C)C=C or an other, or some mix. The product should offer a lower melting point, a higher flash point, and the reactants are less volatile if not more healthy and stable. Store cold. Ethylene also can be replaced or mixed. A blended product, from mixed reactants or through successive batches or both, uses to offer a lower melting point and viscosity.

Is the (substituted) dicyclobutyl-cyclobutane alone better than Boctane? Denser and less flammable, but what melting point? It should be feasible from divinyl-cyclobutane (see Orgsyn's paper) and ethylene, or (1,3-?) from vinyl-cyclobutane. Or start from 3-methyl-hexatriene, available from rubber pyrolysis, which seems to cyclise less than hexatriene, and could have been the reactant to Syntin. Prefer blends as usual.

Divinyl-cyclobutane could be cyclopropaned instead. Isomer of the old Syntin, same performance. Substitute and blend.

More distant enes in the reactant would make a product more flexible and unsymmetric than Boctane. Less dense, but lower melting point. If the melting point improves enough, a third ring would regain density.

A bit of cyclobutane is acceptable in the fuel (cubane as well, thanks); excess might be sold, reverted to ethylene (in real time?), converted separately to Boctane if possible. Cyclobutene should be stripped and reverted to butadiene.

Xe2 lamps to produce cyclobutane could be interesting by themselves, even if not to make Boctane. It could even be possible on Mars; cyclobutane needs less hydrogen brought there than to produce methane from the atmosphere - though I'd instead burn hydrogen with local oxygen, or rather bring the propellants.

If exciting only ethylene, both steps might occur in the same reactor... Or if providing light at both wavelengths for butadiene and vinyl-cyclobutane... Then, vinyl-cyclobutane must be gaseous and cyclobutyl-cyclobutane better liquid. Mind cyclobutane amount as well. Less easy to tune!

The inspiring paper at Orgsyn excites Michler's ketone around 336nm from medium-pressure mercury. Usable for vinyl-cyclobutane? Optimum sunlight brings 4W/m2 between 336nm and 306nm.

Comments welcome!
Marc Schaefer, aka Enthalpy

[Enthalpy]

I went the wrong way and you didn't tell me a word...

Because ethylene and butadiene give a "good yield" of vinyl-cyclobutane over titanium catalyst.
And butadiene dimerizes to cis-1,2-divinyl-cyclobutane over nickel(0) catalyst.
From http://onlinelibrary.wiley.com/doi/10.1111/j.1749-6632.1973.tb49527.x/abstract
"The catalyzed codimerization of ethylene and butadiene to vinylcyclobutane" by Lawrence G. Cannell

So at least the first step needs no UV light.
In case the second step is a cyclopropanation instead, it needs no light neither.

Excimer lamps are recent. Most literature refers to mercury lamps, at medium (wide 336nm) or low (narrow 254nm) pressure, which means excitation of most molecules had to be indirect. Excimer lamps could change the reactions' selectivity and photon efficiency - or it's wishful thinking.

[Enthalpy]

By photosynthesis, textbooks tell that butadiene can become cyclobutene and two cyclobutene a 3-ladderane, which makes a desirable rocket fuel, or rather its substituted variants...

Textbooks don't reveal one thing... If you know the yields, please tell! The amounts of light would be interesting also.

Cyclobutene appears to live long enough at room temperature, reverting to butadiene around 175°C rather. Though, polymerization competes with the ladderane. Dilute and chill? It looks risky at industrial scale.

[curiouscat]

Dilute and chill? It looks risky at industrial scale.

Why?

[Enthalpy]

My paragraph was just badly built, oops. The use of cyclobutene might be risky, less so if chilling and diluting.

Cyclobutene seems to polymerize willingly and once this heats it, can release energy when transforming into varied things. Similar to the risk of butadiene; cyclobutene might be less prone to polymerization than a conjugated diene, but it releases more heat once it decomposes.

Well, it's a matter of amounts... Producing 200t in 20 days can mean big batches, but a continuous process would minimize the amounts at the plant.

I've found no safety data about ladderanes. Gram amounts are big news, so their risks can't be well known.

By the way, a rather recent ladderane production method holds two identical molecules close together, each with a C=C-C chain, and irradiates them with UV. If one could make the same with two (substituted) benzene rings to produce hexaprismane, it would bring 2/3 of cubane's advantage as a rocket fuel... The evenly spread strain of hexaprismane may (?) give it stability, and perhaps it's less difficult to produce than cubane.

A lone excited benzene ring is known to isomerize, supposedly before reaching the next benzene since no hexaprismane was reported from these experiments, thus the two stacked rings. Six new bonds may also require an excited level that is not the lowest one. And as a wild extrapolation, substitutions at different positions on both rings may favour the required excited state.

Marc Schaefer, aka Enthalpy

[curiouscat]

If one could make the same with two (substituted) benzene rings to produce hexaprismane, it would bring 2/3 of cubane's advantage as a rocket fuel.

Hmm....I didn't understand how you calculated that. Advantage = energy capacity?

[Enthalpy]

Only a software like Propep or RPA can evaluate the performance of rocket propellants,
http://www.propulsion-analysis.com/
as it depends on the elemental composition (more hydrogen is better because H₂O is light), the isentropic coefficient (N₂ and CO convert better the pressure ratio into kinetic energy), and the heat of formation of the fuel (less hydrogen for more strain; multiple bonds are unwanted).

Alas, I have only AM1 and the like to estimate the fuels' heat of formation as a liquid at RT, and have nearly zero confidence in it, hence the voluntarily vague estimate of "two-third". Pure cubane (solid if not substituted) would improve the gas ejection speed by some 180m/s over kerosene and hexaprismane by some 120m/s, but this is very inaccurate.

120m/s (over 3300m/s for kerosene) isn't a game changer. Only hydrogen (4300m/s) makes a dramatic difference with hydrocarbons. But in existing designs, Boctane (+50m/s) gains like 8% payload in orbit, for which people want to pay. 120m/s would be an interesting improvement even for a new rocket design, not just a retrofit.

Though, hazards and some nuisances would let me give away 120m/s improvement:
(1) Explosion. A launcher has 800t of propellants. Nitromethane is abandoned, hydrogen peroxide nearly so, even N₂O has killed a worker recently.
(2) Toxicity. MMH would bring performance but everyone wants rid of it.
(3) Fire. Kerosene has +55°C flash point, I wouldn't take cyclopropane for 100m/s more. Boctane at +20°C isn't perfect.
(4) Hypergolic ignition is often told as an advantage... But we have igniters for that. Leaks igniting is a serious drawback of amines if nitrogen tetroxide must be used somewhere.
(5) Melting point and viscosity, depending on where the propellant goes... Mars.
(6) Price, yes.

A really funny narrative by an early developer of rocket propellants:
Ignition! An Informal History of Liquid Rocket Propellants, by John D. Clark
http://library.sciencemadness.org/library/books/ignition.pdf
these times are over. Presently, we have solids, and hydrazine/N₂O₄ being phased out, and oxygen combined with hydrogen or RP1 (special kerosene). Boctane is one attempt to improve over kerosene and keep compatibility.

[Enthalpy]

Since cyclobutene is reported to become excited by UV light and even dimerize to 3-ladderane, maybe perhaps potentially... it could combine first with acetylene or an alkyne, building one or more rung(s) before closing the longer ladderane.

How an ignorant like me imagines it (log in to see the sketch below):
- Use a UV wavelength absorbed by cyclobutene directly, without a sensitizer, and not by acetylene.
- Excimer lamps exist now and give choice for the wavelength: better than mercury.
- Put both cyclobutene and acetylene at moderate partial pressure, so light makes a reasonable path. Or stir well. Or both!
- Have some clean non-reacting gas (Ar? N₂?) at the proper pressure (10b?) to broaden cyclobutene's absorption and include the lamp's wavelength.
- Adjust the cyclobutene-to-acetylene ratio to drive the mean length of the ladderane.
- Alternately, choose the temperature and pressure so that the desired half-length ladderene condenses, and (co-) dimerize it in a later UV step.

Longer ladderanes would near the benefit of hexaprismane as a rocket fuel: far better than Boctane, 2/3 the benefit of cubane. And anyway, more people would like to have some, first as an exotic toy, and later they may find uses.

Marc Schaefer, aka Enthalpy

[discodermolide]

You ever considered patenting your ideas?

[Enthalpy]

I considered patents, yes...

They make governments and patent attorneys richer, and inventors poorer as a mean result. Protection in the UE, US and Japan (China?) would cost many k€ initially, and more every year, for each invention.

A patent gives the inventor only a means of proof. Once a multinational company has decided to infringe your rights, you still have to win a legal action against them.

My employers patented some of my inventions - but not the RFID! - and earned no cent through these patents. Individual inventors who can make companies pay for ideas, like Roland Moreno did, are even less common.

As a result, I prefer to give away for free the ideas I won't develop by myself.

Worse: I understand approximately nothing from chemistry, so most of my ideas here, especially synthesis routes, must be nonsense. Luck helped other people for the production of fullerenes, but miracles are scarce. Chances are better at other ideas, like the quick production of ice, the reactor with rotating disks, the electrostatic alternator, the extruded rocket tanks, the transcranial magnetic stimulation...

Good luck to people willing to try them!

[fledarmus]

@ Enthalpy - there is something to what you say, but in many cases I think that is because many of the people trying to get patents, especially their first patent, see the patent as the end of the process. It isn't. Patent protection is simply one step in the process of commercializing an invention - an important and necessary step, to be sure, but not as important as actually producing the product.

The idea that having a good idea and rushing out to get a patent on it will be the key to wealth is seriously overblown. A successful inventor must be willing to carry an invention through from idea to prototype, to commercial embodiment, to marketing, and in the meantime to work on improvements and new inventions.  Getting a patent along the way is essential to keep the next person from simply looking at all your hard work and saying "I can do that", without going through all the hard work of development. A company that is truly interested in product development rather than copying will usually be able to design their way around your invention if the solution is really important to them, and if your patent isn't something they are already working on, there is very little incentive to develop it if you haven't already done all the legwork to make it productive.

[curiouscat]

Worse: I understand approximately nothing from chemistry, so most of my ideas here, especially synthesis routes, must be nonsense. Luck helped other people for the production of fullerenes, but miracles are scarce. Chances are better at other ideas, like the quick production of ice, the reactor with rotating disks, the electrostatic alternator, the extruded rocket tanks, the transcranial magnetic stimulation...

Do you keep them as ideas or have you built prototypes for any? e.g. the rotating disc reactor I'd be interested in seeing how it operates.

[discodermolide]

Worse: I understand approximately nothing from chemistry, so most of my ideas here, especially synthesis routes, must be nonsense. Luck helped other people for the production of fullerenes, but miracles are scarce.

[/quote]


I find it difficult to believe that you know nothing about chemistry, even approximately. Some of the reactions you have presented to us may just be feasible so why not try them out experimentally? This because chemistry is an experimental science and you never know until you try!
On the other hand by publishing your ideas here you are preventing others, who may be thinking along similar lines, from being able to patent their ideas (I am thinking more of companies here, not individuals).
Also I find it strange that, as you said you understand "approximately nothing from chemistry" , you are posting these ideas at all. The object of this forum, apparently, is to educate those who have difficulties with the subject, so what are you learning?

[Enthalpy]

Honestly, I have no academic degree for chemistry (I've degrees for electronics and made other things meanwhile, like a satellite or facilities for crash-test), and worse, I experimented last time with chemistry as a teenager... So while I look with envy to the University's chem labs next to my home, I doubt they would let me in, nor would I make useful things there.

Hence what I suggest on Internet forums is more a message in a box, available for everyone, generally untested. My proposals for electrical and mechanical engineering are likely to work, but for chemistry not likely.

Try by myself: I have nothing here! I came with my backpack and got my computer meanwhile.

I keep a few other ideas for me, which I can develop by myself with an investment accessible to an individual, and which don't compete with Exxon-Apple-etc.

[Enthalpy]

Silicon boule are hold at their seed only because of their outstanding strength. As soon as the final diameter is grown from the seed, a normal material can be grasped there.

Strength depends on the material... Sugar for instance can make big solid parts that don't break. Single-crystals also differ from polycrustalline or amorphous materials; they're often much stronger but brittle.