Hydrogen Cars and Fuel

There is no question that Americans drive a lot of cars, and in turn those cars burn a lot of gasoline.

Result? Pollution!

Not to mention heavy dependency on foreign sources of oil, and all the headaches that come along with that.

Hence , there's interest in alternative fuels, and high on the list is hydrogen.

In theory, hydrogen seems like the silver bullet—when you burn it, you get water (as 'benign' an emission as you could wish), and of course it's availability--hydrogen is the most plentiful element in the universe.

In actual practice, however, hydrogen is no quick fix. Hydrogen makes up the majority of the mass of the Sun, but here on planet Earth the traditional source of hydrogen gas—what we'd use in a fuel—has been natural gas—a fossil fueland a very limited resource. It is obvious you're not solving an energy crisis by switching to a fuel still derived from fossil fuel. There is some promising research aimed at getting hydrogen fuel from other sources, but commercial applications are not yet here.

Looking beyond the question of obtaining hydrogen gas, and building cars that could use it, there's another very significant problem with shifting to a hydrogen-based economy: the problem of distribution.

How, exactly, is all this hydrogen gas going to get to your car? We have a network of local gas stations if you need to fill up your gas tank, but you can't really pull into one of them and say, "Fill it up with H₂, please." Even assuming we had the hydrogen gas in the first place, there are problems.

in the first place, gasoline is actually not a gas but rather a liquid, however hydrogen gas is a gas and cannot therefore be pumped into your car by the local gas-jockey.

In addition transporting it in gas form is not a good idea, because it's explosive when mixed with air.

The solution,it would appear, is to liquefy it. And indeed that is possible. All you have to do is lower the temperature to −423.17 °F and keep it highly pressurized, otherwise it returns to its gaseous state.

Possible, but not easy.

This distribution difficulty will have to be solved one way or another before hydrogen is feasible. The research of Robert Crabtree at Yale University and Eric Clot and Odile Einstein (of Université Montpellier in Montpellier, France) seems to indicate that maybe there is a way to make liquid hydrogen more practical.

he radically low temperature and high pressure required to keep hydrogen in a liquid state make that approach an impossibility.

An alternative that researchers have been looking into is using an organic liquid that would incorporate hydrogen in its structure—then, inside the car, the hydrogen would be removed from the carrier liquid and used to run a fuel cell, providing electricity that would make the car run.

Recently researchers have investigated using a heterocyclic compound, an organic compound with a ring structure made up of carbon and other elements.

The starting point is the heterocyclic compound, called a fully dehydrogenated carrier.

Hydrogen is injected into the carrier through a complicated process called hydrogenation to create a generalized hydrogenated carrier. This is the actual stuff that would get pumped into your hydrogen car's "gas" tank.

While inside the automobile, to free the hydrogen for use in a fuel cell, the organic liquid would be mixed with a catalyst and heated until the hydrogen atoms break their bonds.

Once the hydrogen has separated from the mixture, it is put to use in the fuel cell, while the now-dehydrogenated liquid is returned to the vender to be rehydrogenated and reused.

So not only does the hydrogen burn in an environmentally safe and clean  manner, the carrier liquid gets recycled.

How cool is that?

In essence, this  is how researchers envision a liquid hydrogen refueling scheme working.

However there is a problem lurking. 

Current carrier liquids don't release  their hydrogen very easily.   In order to break the bonds and free the hydrogen for use in the fuel cell, the carrier must be warmed up by about 600 °C (1112 °F).

In factories and laboratories this is feasible, but it's not feasible for millions of cars.

The final part of the puzzle is in figuring out the optimal placement of the nitrogen atoms in order to achieve dehydrogenation. And this must occur at the minimal most temperature level.

Experimenters discovered that five-membered heterocyclic compounds were capable of achieving much lower temperature ranges for dehydrogenation than six-membered rings.

They also determined that the best positions for nitrogen atoms (in the fully dehydrogenated form) in five-membered rings are in positions 1, 2 and 4, with an extra H bonded to the nitrogen atom in the 1 position.

There are problems that need to be ironed out for commercial useability, and queries related to large-scale production and toxicity will have to be solved.

According to Crabtree, the liquid won't be rendered harmless but will be no more harmful than our present fuel (gasoline).

In addition, the density will be almost the same as gasoline's density.

As far as onboard generation of hydrogen, the catalyst involved in the reaction would most perfectly (from a chemical point of view) be rhodium or platinum, but since these are expensive, some suitable substitute will need to be found.

Conclusion?

With the growing interest in the ecology of our planet, and the need for self-sufficiency in fuels, America and the world at large will no doubt continue high-intensity research in the area of hydrogen fuels and cars that run on something less poisonous, expensive, and politically dangerous, as gasoline and oil from the middle east. 

It's just a matter of time.