Water plays the role of catalyst in explosives

March 21st, 2009 - 2:45 pm ICT by ANI  

Washington, March 21 (ANI): Scientists at the Lawrence Livermore National Laboratory, US, have shown that water, in hot dense environments, plays an unexpected role in catalyzing complex explosive reactions.

A catalyst is a compound that speeds chemical reactions without being consumed.

Platinum and enzymes are common catalysts. But water rarely, if ever, acts as a catalyst under ordinary conditions.

Detonations of high explosives made up of oxygen and hydrogen produce water at thousands of degrees Kelvin and up to 100,000 atmospheres of pressure, similar to conditions in the interiors of giant planets.

While the properties of pure water at high pressures and temperatures have been studied for years, this extreme water in a reactive environment has never been studied.

Now, using first-principle atomistic simulations of the detonation of the high explosive PETN (pentaerythritol tetranitrate), the team at the Lawrence Livermore National Laboratory discovered that in water, when one hydrogen atom serves as a reducer and the hydroxide (OH) serves as an oxidizer, the atoms act as a dynamic team that transports oxygen between reaction centers.

This was news to us, said lead researcher Christine Wu. This suggests that water also may catalyze reactions in other explosives and in planetary interiors, she added.

This finding is contrary to the current view that water is simply a stable detonation product.

Under extreme conditions, water is chemically peculiar because of its frequent dissociations, Wu said. As you compress it to the conditions, you would d find that it in the interior of a planet, the hydrogen of a water molecule starts to move around very fast, she added.

In the molecular dynamic simulations using the Labs BlueGene L supercomputer, Wu and colleagues found that the hydrogen (H) and hydroxide (OH) atoms in water transport oxygen from nitrogen storage to carbon fuel under PETN detonation conditions (temperatures between 3,000 Kelvin and 4,200 Kelvin).

Under both temperature conditions, this extreme water served both as an end product and as a key chemical catalyst.

The team found that nitrogen loses its oxygen mostly to hydrogen, not to carbon, even after the concentration of water reaches equilibrium.

They also found that carbon atoms capture oxygen mostly from hydroxide, rather than directly from nitrogen monoxide or nitrogen dioxide.

Meanwhile, water disassociated and recombines with hydrogen and hydroxide frequently.

This new discovery could have implications for scientists studying the interiors of Uranus and Neptune where water is in an extreme form, Wu said. (ANI)

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