New Process Promises Ammonia From Air, Water, and Sunlight 117
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.
Nitrogen Cycle (Score:3, Interesting)
Ammonia fuel (Score:5, Interesting)
Something not mentioned here is that ammonia is suitable as a fuel in internal combustion engines. Ammonia is liquid under modest pressures (like propane), is easily transported, and will burn inside an engine.
If we made ammonia out of nitrogen and water vapor, then it would become nitrogen and water vapor again when burned. It's a closed cycle that would not alter the composition of the atmosphere at all.
It probably wouldn't be suitable as a fuel for your car, because of safety issues (if you hammered a hole in the fuel tank, the fuel inside would flash boil and could shoot out into your eyes causing a chemical burn). However it would probably be fine for trains, airplanes, ships, and so on, where special handling procedures could be enforced and people could be required to wear goggles before working on the fuel tank.
Re:Ammonia fuel (Score:5, Interesting)
How would that be more dangerous than propane? LP gas would do exactly as stated above, if someone poked a hole in a fuel tank with their drill, they would get sprayed by rapidly evaporating fuel.
IMHO, this might be the way to have a hydrogen economy. If a nitrogen fixing process is easy and economical, making liquid ammonia is a lot easier and requires less pressure than converting water to hydrogen via electrolysis.
The downside is that ammonia has a bad rep here in the US. Because it is a major ingredient in meth, anhydrous ammonia tanks tends to be a prime target for "lab assistants" to obtain their reagents. However, if done right, ammonia might just be what is needed to make the "hydrogen economy" a reality, because it has a decently high energy density.
Of course what would be nice would be a fuel cell that uses ammonia directly without the conversion to hydrogen.
Re:Ammonia fuel (Score:5, Interesting)
Ammonia is caustic and would cause a chemical burn on the surface of your eyes, unlike LP.
It seems much more sensible to use ammonia than hydrogen gas, because ammonia has handling and storage properties similar to propane which solves the major problem of hydrogen gas.
It makes a big difference if you can store something as a liquid and transport it through pipelines. That explains why oil sells for 10x more than coal, per BTU, and several times more than natural gas.
Re:This could be great (Score:3, Interesting)
Chlorate based explosives are easier to make than nitrate based ones. All you need is a bag of road salt, electricity, and a pot of hot water at 60C, and some carbon anodes that don't get chewed by the chlorine gas. I think matches are made from chlorates, but you have to shave a lot of match heads down to get any kind of punch. I remember when I was a kid we used to have fun making exploding noises from match heads. All you need is two male screw bolts and a female nut, about 3/8-1/2". You dp (double penetrate) the female nut from both sides with the two male bolts, and have match shavings between them. I mean you only screw one of them in halfway, shave the matches like into a cup, then screw the other one on very very tight, then loosen like a 10th of a turn, or don't even need to loosen it. Now you take a piece of plastic bag, or even a rag, and tie it to one of the bolt head ends, to make it into a tail, to create aerodynamic drag. with a piece of wire. About a 4 inch or 6 inch tail should suffice on a 1/2 inch set of bolts, that are like 12 inch total length when assembled. Pick it up by the tail, and swing it real high up in the air, so that when it comes down, it comes lined up nicely with the bare bolt aiming directly toward the cement or even asphalt sidewalk, and the plastic bag aerodynamic drag tail end pointing up. When it hits the ground, the contents explode from the sudden shock, and make a really nice, loud noise. Then you can go pick it up, unscrew it, reload, and do it again, but it does eat a lot of matches, like 3 shots out of a small matchbox of 50 matches. We also used to have fun with carbide, (calcium carbide) we stole from the welding acetylene generators from the nearby construction sites. You'd drop a small piece into a wine or beer bottle that the drunkard construction people would leave laying around empty, filled 3/4 with water, then cork it (back in the day they had corks), and wait til it goes pop, and shoots the cork up real high in the air. Then find the cork again, and re-cork it, and repeat. Not as fun as the double screwed match explosion, but it's cheaper when you're so broke, that you can't afford to buy matches under a communist regime, but the calcium carbide is free, you find in for free in the acetylene generators at the construction site. Of course you gotta go when the security guard is gone drinking his sane mind away at the nearby pub, and when he comes back all drunk, he can't run straight to catch you. We all knew the most important trick when running from the security guard if you accidentally bump into him while playing hide and seek, is to run, and when running, take sudden sharp turns, and being a 7 year old kid and him like a 50 year old, running in huge safety rubber boots compared to your tennis shoes, he has a lot of inertia and keeps running straight, and you can escape like that. But one time one of them conspired with a regular on the street person, who was walking her girls, and grabbed me, for him, and I couldn't run away, so I had to take him home, and my mother, to appease his anger, gave him some brandy shots. And all was good, and he wasn't angry at me from than on when he saw me from the distance, because he remembered the free alcohol, but he was still orchestrating ways in his mind to catch me again and get some more alcohol, and I, and my buddies, we had to be careful not to get caught. But we had creative ways to have fun and kill time after coming home from standing in line for bread for like a whole friggin hour, til the bread truck arrived. When you're a 7 year old, and there is a moblike crowd that starts stirring when the line breaks down (kind of like a crowder concert, where people are really excited and try to get close to the stage) sometimes you get lifted from two sides and your feet don't touch the ground, and get carried like that til you land on your feet again, and people acted like that because sometimes the ones at the end would be told that that's it, come back later, we're out of bread. So anyway, we also used to steal half inch