Mechanical "cutting" of long hydrocarbon chains

I seem to remember a machine that actually "cut" motor oil into shorter HC chains to test motor oil longevity. Would it be possible to mechanically crack HCs into fuel on a large scale? How about pressing HCs through rollers so precise that they would actually crush molecules to do the job? The trouble I see would be that people would start disappearing into fuel tanks, chubby people would be the first to go.

Reply to
Loading thread data ...

You probably could, but, like fusion, the issue would likely be: can you control the resulting products?

This is actually a very inneresting notion, and, perhaps, uh, cuts to the core of chemical reactivity/bonding.

To mechanically cut organic molecules *within the molecule* (as opposed to say, fracturing a crystal lattice, as in steel, or undoing much simpler hydrogen bonds/protein interactions such as in cutting wood) would actually involve a net chemical reaction, which may be difficult to control after mechanical breaking.

Cutting something also raises the almost as dicey concept of what it means to just touch, or even move something. Think London forces. :) But back to cutting:

If you were to actually "mechanically break" a hydrocarbon chain in half, you would temporarily have two free-radical like carbons, highly reactive. And the question would be, what would they then react with?

What you would want is a hydrogen atom replacing each half of the previous C-C bond, but the now-unstable carbons might instead react with the cutter itself, possibly something else, or likely just with each other, simply recombining.

Reaction with the cutter itself would be very likely, because the "cutting" is actually one set of molecular/atomic orbitals disrupting another set of molecular orbitals. When orbitals become that intimate, interaction is almost inevitable. Esp. when you visualize a "molecular press/roller" situation.

This suggests that the "cutting" would have to occur on the surface of some catalyst (think platinum, as what's in your car), and would involve some very sophisticated solid-state chemistry.

The other way to mechanically cut a hydrocarbon chain would be to grab (read: bond in some way) with the ends of the chain (like in a tug of war), and just pull, until somewhere in the center breaks.

This then becomes its own conundrum, because then how would you reversibly release the ends? And, you would still have the reaction problem of an unstable middle.

The line between the mechanical and the chemical is always an inneresting notion. For example, in hydrocarbons, the transition from gas to liquids to solids is a very nice mechanical continuum, from methane to asphalt, and arises solely from the *length* of the hydrocarbon chain!

Methane is the way it is (a gas) because the chain is short -- just one carbon; kerosene is about 8 carbons or so, forming a liquid; asphalt is

30-60 carbons, one chain literally knotted up with another (and maybe even itself) like a a pile of strings, ie, a mess. But, apparently a very useful mess.

Enzymes are what mother nature uses to "cut" molecules, and is akin to a fixture on a BP, as opposed to a wielded ax: Molecules are is held precisely (and reversibly) in place, as the orbital surgery takes place, just as the fixture on a BP holds the material, and the BP itself holds the fixture and the cutter. Once the surgery is completed, the molecules are released -- like opening a vise. Pretty incredible, actually, yet so routine in living systems -- actually, the foundation.

In this scenario, you even have the literal concept of "tolerance", just as you would, say, in a punch and die set. An enzyme's effectiveness in catalyzing reactions (cutting/stitching) is directly proportional to how well substrates "fit", and chemical poisoning often proceeds by creating unworkable tolerances, especially in metallo-based enzymes (which use copper, zinc, iron, magnesium, selenium, etc).

Cadmium is one very elegant example of this poisoning, as it is orbitally similar enough to zinc (iirc) to replace it in the enzyme system, but dissimilar enough to disrupt the dimensions/tolerances of the enzyme that depends on zinc to function in its molecular cutting/stitching.

Apropos of the above oh-so elegant transition from chemistry to machining, most here would find the notion of "molecular motors" beyond fascinating. The biochem text by Voit and Voit shows pictures of some molecular motors (eg, the rotating flagella of some bacteria), and your collective jaws will hit the floor when you see nature's version of rotors, stators, bearings, shafts, and the like. It is *beyond uncanny* -- eerie, even -- and well worth a google search to try and see these. Hard to imagine this not being on the web.

I doubt, however, if you will find a molecular IC engine, but who knows.... Bomb beetles come close, tho...

Btw, not saying the raw mechanical cutting molecules can't be done, just that there are bevies of details to what would ostensibly seem a trivial process.

Reply to
æx?URKoÔ0¾çWÌi/¬ â²}QÊa9 J?³ãÆfmO°?òï;ihÏ÷´»î)?a¸ú°?«?ïuØÃîO!¾þR0eÆå;¿L?R?5³2v£Ì/??»kÇo0A?aÀ?6ÖE¶?A.ÚûyU1?W?@L ÈypQðÙRboozw×=nÆjs?`Ìü æ)?ø×ñ¬@?ü¢âOà??rv?Ç

(Ñíb?ÿgN?áø?Ï=P?^§! ï+÷?. * SB¡?cC±MTFÛh_8y/=B¦ºk\^k`?3\???J¶?)[ÄÕMøMÃâö~#þ)c½«µ¾² «??4ù?afN.ëiBªá-⻬ã9ï¥ã2 ó[?F?ðìäWTk#©íDû?y:ô=Fuqg7áÉiEiìë©ÿÞ:'c1¸Ìiî|®4 ûòüá?ô ?¼\îÙ(?,é¼5(f°>rîe?ìt?®¿?^^#«îß#þ .

Reply to
Denis G.

Thanks for the wonderful chemistry lesson! I have this "Brain Candy" notion that somebody will stumble on something stupid-simple that will solve huge, complex least I hope!

Reply to

What huge problem???

formatting link

Reply to
Jim Wilkins


formatting link
google "mechanochemical + fuels", etc. I think that the field is mostly R&D at present.

Fascinating! Thanks.

Reply to

"Buerste" wrote: (clip) Would it be possible to mechanically

^^^^^^^^^^^^^^^^^^^^ Remember the term "cat-cracking?" Refineries reduce the molecular weight of crude oil to produce gasoline by chemical means, aided by catalysts. The clearances between mechanical surfaces, such as rollers, are far greater than the size of any molecule. If you tried to crush molecules with rollers, they would just slip through the clearance created by the roughness. The viscosity of motor oil in an engine does decrease somewhat as the oil is used, because it is being "rubbed" by the metal surfaces, causing some of the molecules to break down into shorter lengths. However, it is not controlled, and it is very slow compared to cat cracking.

Reply to
Leo Lichtman

Yes, in fact, there was once a machine, which looked rather like an old fashioned laundry wringer, which operated on this principle, and took in grass clippings and used newsprint, and output gasoline and oxygen. Big Oil bought up the patents, and it was never heard of again.

Reply to
Richard J Kinch

Stupid simple: I just wish I had thought of registering $10 mil, fast. Woulda solved a lot of huge problems. :(

Cupla extree thoughts:

The roller idea is inneresting, but likely fundamentally unfeasible, because of the inherent "roughness" of orbital geometry in molecules.

iirc, if the nucleus of an atom were the sun, the electron orbitals would resemble the planets -- or some such thing. And it is, of course, the electrons/orbitals which are doing the interacting.

Bottom line, the smooth carbon-backbone chain, or DNA for that matter, that you see in pitchers, is far from smooth.

A "molecular roller" that is "flattening/tearing" other molecules would be like two sheets of 24 grit sandpaper sandwiching strands of hair, trying to slicing them.

If you made the roller out of a really small atom, say lithium, beryllium, or boron, you might have a shot at flattening/tearing other molecules "mechanically", but even that would proly be remote, and not controllable.

There are example of molecules snapping, however. Two examples I can think of off-hand, involving ring strain.

But first, note that in carbon chains, the zero strain configuration for

*closed rings* is a hexagon, ie 6 carbons, of which cyclohexane (a liquid) and benzene (also a liquid), are two classic examples, but in distinctly different ways, having to do with hybridization. Glucose is a classic example of a the cyclohexane type, which is actually a "puckered" hexagonal ring. Benzene is a flat ring.

Pentagonal configurations are also pretty stable (fructose is a great example), square is substantially strained, and triangles are very rare and super strained.

  1. The fragrance of the chrysanthemum flower has what's known as an "epoxide ring", which is a very very unusual molecule, in that the ring is triangular ( a C-O-C, iirc), which means extremely high bond strain. What is even more remarkable is that this compound is *natural*. It will, on very little provocation, pop open to a linear open chain. IOW, it "breaks". Which may provide the fragrance, altho I'm not sure.

  1. Penicillin acts via a square ring, C-C-C-S, iirc, and also substantially strained. Its antibacterial action occurs when the ring pops open (breaks), and the very reactive sulfur now attacks the bacterial membrane. Or so I vaguely remember.

But anyway, these are the best examples I can remember of molecules just "breaking". In these cases, the stress is internal, and the molecule eventually gives way, but nevertheless it does set a kind of precedence for the notion of "mechanical breaking".

But, proly not through rollers.

One poster pointed out that the rubbing of cylinders is a factor in altering the structure of oil.

This is probably not the case, as explained above. It is likely simply pressure and temperature effects (and time), both of which are important factors in making reactions go or not. And, the metals in the engine could act as catalysts, as well. Unlikely that mechanical rubbing has anything to do with it, other than as a source of very high pressure by which to make a reaction go.

Evidence for this would be that in used oil, the products are not cleaved hydrocarbon chains (which are already pretty short to begin with), but rather cyclic, heterocyclic and polycyclic aromatic rings -- ie, derivatives of benzene, often with nitrogen.

Which happen to carcinogenic, or so they say. Not all benzene derivatives are carcinogenic, and in fact many are common moeities in biological systems. Benzoic acid, phenylalanine, many others.

Inyway, it is really intriguing how the nitty-gritty of atomic and molecular orbitals, and all the quantum mechanical mumbo jumbo therein, can be distilled into simple notions of mechanical "strain".

You can buy molecular modeling sets, which have all the standard bio-atoms in their various hybridized geometries, and you can actually put together "angularly accurate" models of molecules and literally "feel" the strain in them, ergo their instability and "breakability".

Iow, as you put these models together, cyclohexane/glucose/benzene go together very easily, while epoxides and penicillins have to be wrestled with, to assemble them.

Reply to

Umm. What are the patent numbers?

Joe Gwinn

Reply to
Joseph Gwinn

And here I was hoping for a mechanical device that one could put anything in one end and strings would come out the other and fall into a bin. Now, if they would only stay in our dimension.

Reply to

On Mon, 13 Oct 2008 21:52:21 -0400, the infamous Joseph Gwinn scrawled the following:

Excellent question. I also want the patent number on the 200mpg carb and several others.

-- "Politics is the art of looking for trouble, finding it whether it exists or not, diagnosing it incorrectly, and applying the wrong remedy." -- Ernest Benn

Reply to
Larry Jaques

99% of patents are irrelevant, unworkable, impractical, useless, or outright bogus. Most have never even been built.

The ONLY thing the USPTO won't issue a patent for is perpetual motion machines. Hooray thermodynamics..... The USPTO does not require working models, except for perpetual motions machines.

Also, they are often not easy to understand, as they are written as cryptically as possible.

However, there could be hidden gems in them thar stacks. I think we're up to 7,000,000 patents, just in the USA. Much of the modern patents is subtle electronic design stuff.

Reply to

Oh yeah, not to mention, that patents are pretty much unenforcible, and indefensible, unless you are IBM duking it out with HP et al.

Just the retainers for patent litigation start at about $50K -- kiss yer dreamed-of profits goodbye, whilst you send sed attorney's kids to ivy league school (private dorm, of course), and his gold-digging wife on yet another cruise....

-- PV'd

Reply to

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.