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New Process Promises Ammonia From Air, Water, and Sunlight
The synthesis of ammonia is one of the globe's most significant industrial applications of chemistry. PhysOrg reports the publication in the August issue of Science (sadly, article is paywalled) the description of a low-energy process to syntheize ammonia for fertilizer using just air, water, and sunlight, by zapping with electricity water bubbling through a matrix of iron oxide, and sodium and potassium hyroxide. Electricity isn't free, though — "Low energy" in this case means two-thirds the energy cost of the long-in-use Haber-Bosch process. Researcher Stuart Licht is getting some of the energy to run this reaction from a high-efficiency solar cell he's created, which creates hydrogen as a byproduct.
Along with the elimination of the need to produce hydrogen from natural gas, the overall emissions are reduced quite significantly. The whole process also takes place at milder conditions, not requiring 450C and 200 times atmospheric pressure as the Haber-Bosch process does. ... But even with Licht's method, [University of Bristol electrochemistry professor David] Fermin points out that we are far away from being able to replicate nature's efficiency at converting nitrogen from the air to useful chemicals, which is done by nitrogen-fixing bacteria. "What is truly remarkable is that nature does it incredibly efficiently at low-temperature," Fermin added.
And yet, if something more efficient can replace the Haber-Bosch process, it would lower the energy input of the production of one of the worlds most important chemicals and lead to a notable reduction in global CO2 emissions.
Here's some background on the Bosch Haber process.
Whether a reaction will occur is based on whether energy is required and whether the reaction increases entropy. In the case of nitrogen+hydrogen => ammonia, the reaction is both exothermic and increases entropy at room temperature and pressure. If one could somehow ignite the process it would be self-sustaining.
The problem is, to ignite the reaction you first need to break N2 molecules into individual N atoms, and this requires a great deal of initial energy which is regained in subsequent steps. Something like 7eV per molecule to break them apart. The molecules in normal air have a bell-curve spread of energies, but very few of them reach energies this high: the reaction happens at room temperature, but very *very* slowly. A handful of molecules per second will react.
To get around this you can raise the temperature, increasing the probability that molecules will have enough energy to break apart. The entropy produced is inversely proportional to temperature, so when you start to have N2 molecules with enough energy to break apart, the reaction is no longer favored because it would result in an entropy decrease.
Since 4 moles of reactants result in 1 mole of product, increasing the pressure of the reactants will tend to favor the products, so you can use this to offset the deficit in entropy.
The Bosch-Haber process tries to find a "sweet spot" by increasing the temperature to get a reasonable number of N2 molecules to break apart, and high pressure to make the process favor the products.
At 200 ATM and 400 degrees, the yield is 15% (!).
Reaction vessels for this pressure and temperature are expensive, and the process requires multiple cycles of compression, decompression, removal of ammonia, and recompression. This takes a *lot* of energy and uses *very* expensive compressors which wear out over time and have to be replaced.
I haven't read the paywalled article yet, but if I'm understanding the abstract, they are breaking apart the nitrogen electrochemically. Just as running a current through molten NaCl will break it into atomic sodium and chlorine, running a current through nitrogen dissolved in KOH and NaOH breaks it apart and the reaction then proceeds at normal conditions. The reaction also supplies its own hydrogen by breaking apart water.
Much of the "green revolution" is due to the use of nitrate fertilizers, and the source material is finite: guano from Peru, for example.
If this process is as efficient as the abstract suggests and can be industrialized, it would be *huge*. It would give us an essentially infinite source of nitrogen-based fertilizer and reduce the worldwide consumption of energy by a couple of percent.
Coupled with a source of renewable energy, it would mean that the world could sustain its food production at current levels indefinitely.
This could be really, *really* big news.
Oh, please. Creating explosives is easy (well, the creating part is easy. The "don't blow yourself up prematurely"-part usually not so much).
You merely need nitrating acid which you get by mixing nitric acid and sulfuric acid. Both acids are relatively easy to obtain (Both acids are sold on Amazon over here). Then you mix the nitrating acid with cotton, dry the stuff carefully and you got: Gunpowder Cotton, also called: Smokeless Gunpowder. All you need is a fumehood because mixing the acids is a bit hard on the lungs.
If you want to up the ante: Use glycerin (a laxative, also easily obtainable) instead of cotton. And, you guessed it: You get Nitroglycerin. However, the nitration process is exothermix and you need to be very careful when mixing the acid into the glycerin or it will blow up.
Those are just two examples. Almost the same process is used to produce TNT, by the way.
Before I get slammed by a P-Chem major, here's what's really going on with the entropy.
The reaction is exothermic, and this release of heat increases the entropy of the universe. At the same time, 4 atoms of source become 1 atom of product, so this aspect of the reaction *decreases* the entropy of the universe. (There's more ways that 4 atoms can be arranged in a box than there is to arrange 1 atom.)
At room temperature, the entropy increase from the release of heat is greater than the entropy decrease from the reduction in states, so the reaction is favored.
The entropy from the release of heat is inversely proportional to temperature. Double the [absolute] temperature and you halve the increase in entropy from the release of heat. With higher temperatures, the entropy increase from "release of heat" is smaller than the entropy decrease from "change of states", the total change of entropy is negative, and the reaction is no longer favored.
I wrote a simpler/shorter explanation to avoid losing sight of the main point.
Drinking Lake Erie water is scarry under the best of circumstances, even Detroit gets most of it's water from Lake Huron north of Port Huron. There is a lot of valuable lipids in that algae for make biofuel. There is a point where reducing nitrogen and phosphorus inputs are going to be effective in reducing blooms because the nitrates and phosphorus already in the eco-system keep recycling, removing the algae removes the fertilizer and breaks down the cycle. The exceptionally cold winter, cold spring, and cool summer also meant there was a very abrupt start to the algae's growth season in the summer rather than a more gradual start in the spring.
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You'd probably want to use a diesel engine for conversion, much easier all around and successfully done back during WW2
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