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Hydrogen as fuel

This morning I was talking with my husband about something or other and we drifted to the subject of hydrogen as an automobile fuel. He was telling me about the new technology they've got where they use ammonia and a catalyst to store the hydrogen in a concentrated and non-flammable format. He was vague on the details, but it sounded interesting enough. So I started grilling him. What's the byproduct of this reaction? How do they get the ammonia in the first place? What are the raw materials?

He didn't have an answer and I have a lot of spare time, so I poked around a bit. So far, I'm not impressed. The hydrogen is either produced by burning fossil fuels or from ammonia-borane reactions. Of course, fossil fuel burning is what we're trying to move away from right? And creating ammonia is bad news too:

Ammonia is the fifth most abundantly produced chemical in the U.S. and ranks number two on the list of chemicals requiring the most energy to produce.

From what I can tell, ammonia is produced by steam reforming of hydrocarbons. So we're back to fossil fuels.

In fact, I don't even know what the by-product of the use of ammonia-borane is. The chemical composition is NHBH + H2. But what the heck is that? From what I can tell it's benzene... but I wouldn't be surprised if I were wrong.

In investigating this, I'm more confused than ever. It looks like hydrogen as a fuel is just as bad, if not worse, than using gas. Someone please tell me I'm wrong.


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AFAIK the basic premise behind "move away from gasoline" isn't "use less energy overall" except as a very secondary goal. It's simply "don't use gasoline."

Number of reasons to do that of course, including moving towards renewable fuels, reducing dependency on OPEC, permitting oil to be instead refined into plastics, etc.

But fuel of virtually any sort requires a lot of energy to produce and distribute. It just happens to be relatively efficient at producing energy when you've got it where you want. Petroleum is easy because the production side is largely taken care of (dead dinosaurs) and you can skip straight to extraction and refining, which are comparatively efficient as opposed to synthesizing fuel in the first place.

(Fuel) chemical compounds that are easy to make (eg liquid hydrogen/liquid oxygen) tend to also be relatively less stable, which is why we don't like them for large scale use.

But you shouldn't be surprised that it's energy inefficient; basically we're taking energy from some (hopefully better) source and expending it to produce a smaller supply of material with high potential energy. That being said, if we could run a set of "solar farms" to produce power and use the electrical output from that to synthesize hydrocarbons, we could produce fuels worth of competing with gasoline. Adding ethanol to the mix may or may not make this more efficient, but makes it more politically acceptable (gain support from farm subsidy PAC). Feel free to replace "solar farms" with "hydro power" or "coal plants" or "OTECs" or "reactors" or whatever your preferred local energy resource is.

On this topic in particular... well, we make a looooooooooooooot of ammonia today anyway (for fertilizers and synthetics like nylon). Production values of that probably are at significant scale; I can't imagine it'd get much cheaper. (But I say that thinking that ruthenium catalysts were already in large scale use, so who knows.)

As I recall, the basic problems with making stable long-chain fuel-capable chemicals are that it's energy intensive and that they tend to be corrosive at one level or another. But clearly it works well enough to make a certain quantity of biodiesel - so perhaps the steam reforming of hydrocarbons can rely on methane or other biodegradation products.

I thought that the appeal of the fuel cell was that it was less polluting? Is it really just an exercize in getting away from OPEC? Some of the sites mentioned using natural gas as a source, but natural gas costs have skyrocketed lately so that doesn't seem like they'd be available in quantities that would be sufficient to account for the way we currently consume gasoline.

Well - less polluting on the roads, perhaps.

It's like saying that electric cars don't produce pollution. It's true, THEY don't. But constructing them is generally no more efficient (and often less), and disposing of a large pile of lead-acid batteries after a few years is kind of a nightmare. More importantly, though, you "fill them up" with electricity from your wall outlet... ok, so you're burning less gas, but drawing more power from the grid, which means that public utilities build more dams or burn more coal or whatever. You're just moving the source of pollution, and it's often more efficient to ship a tank of gas across the country than it is to transmit power over long distances... so it may even be the case that fuel cell or similar electric cars cause more pollution.

Now, that may not necessarily be as bad as it sounds... it at least saves you from brutal smog in cities. But there's other ways to do that, too. (Not that we're likely to adopt those either!)

Ammonia is naturally occurring through a variety of means. Mainly due to organic activity(either decay or normal bio-chemical reactions) or because of volcanic activity. Is it bad? It's bad if you just let it go into the air in large quantities...however, ammonia for manufacture of fertilizers are great. It is also flammable and one of the byproducts is water. Depending on what else is combusted with it will also determine other byproducts. We have all kinds of already existing mass producers that we do very little with (sewage treatment plants, landfills, etc).

Hydrogen is the most abundant element in the known universe and one of the most reactive. Its pretty easy to get (you probably did this in highschool science), run a current through pure water at STP and the hydrogen will strip off and you we end up left with ozone (O3) and hydrogen. If you were to apply fire to that, it would combust and produce water. Theoretically you could create a cyclical process where you combust, and then strip off the hydrogen again. Wash, rinse, repeat.

If you combust hydrogen, you get pure water as the primary by product...looking at that, hydrogen isn't bad. The hard part is the storage and mass production of it. Currently we do not have a good way to store large quantities of hydrogen in a stable "safe" way. There are many projects to get it to a usable "pill" form, where you have a high quanity of hydrogen bonded to some other chemicals. I've seen stuff about converting it to a crystal, or having it bonded to some organic compound. That's the major hard part, getting it in and out of that form. Creating it in the large scale is the same as like Biodiesal...it's the begining set up of the infrastructure and perfecting the process.

As for the result of the ammonia-borane reaction, no it's not benzene (C6H6). Reading the result of the reaction it looks like hydrogen (H2) in a gas state, and some sort of Boron nitrate. I'll poke into it more.


I was hoping you'd know something Mr. Chemistry. :)

All my Knowledge comes from PBS

We don't have cable. We get poor reception. One of the best channels is PBS. We watch a good deal of Scientific American with Alan Alda. He did two episodes on Hydrogen Fuel for cars. Hydrogen Sponge
This link scratches the surface of a technolgy that allows Hydrogen fuel to be stored as an inert (non-reactive) solid. It's being used in some Hydrogen engines now. Once the metal alloy is produced, it can be refilled again and again and again with hydrogen.


Re: All my Knowledge comes from PBS

Thank you for that link! I'm going to have to poke at it.

Here's a rather superficial article on alternative fuels

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