New catalyst turns ammonia into an innovative clean fuel

April 30, 2018, Kumamoto University
CuOx/3A2S selectively produces N2 and H2O from NH3 through a two-step reaction. Credit: Dr. Satoshi Hinokuma

Taking measures against climate change and converting into societies that use significant amounts of renewable energy for power are two of the most important issues common to developed countries today. One promising technology in those efforts uses hydrogen (H2) as a renewable energy source. Although it is a primary candidate for clean secondary energy, large amounts of H2 must be converted into liquid form, which is a difficult process, for easier storage and transportation. Among the possible forms of liquid H2, ammonia (NH3) is a promising carrier because it has high H2 density, is easily liquefied, and can be produced on a large-scale.

Additionally, NH3 has been drawing attention recently as a carbon-free alternative fuel. NH3 is a combustible gas that can be widely used in thermal power generation and industrial furnaces as an alternative to gasoline and light oil. However, it is difficult to burn (high ignition temperature) and generates harmful nitrogen oxides (NOx) during combustion.

Researchers at the International Research Organization for Advanced Science and Technology (IROAST) in Kumamoto University, Japan, focused on a "catalytic combustion method" to solve the NH3 fuel problems. This method adds substances that promote or suppress chemical reactions during fuel combustion. Recently, they succeeded in developing a new which improves NH3 combustibility and suppresses the generation of NOx. The novel catalyst (CuOx/3A2S) is a mullite-type crystal structure 3Al2O3·2SiO2 (3A2S) carrying copper oxide (CuOx). When NH3 was burned with this catalyst, researchers found that it stayed highly active in the selective production of N2, meaning that it suppressed NOx formation, and the catalyst itself did not change even at high temperatures. Additionally, they succeeded with in situ (Operando) observations during the CuOx/3A2S reaction, and clarified the NH3 catalytic combustion reaction mechanism.

Since 3A2S is a commercially available material and CuOx can be produced by a method widely used in industry (wet impregnation method), this can be manufactured easily and at low cost. Its use allows for the decomposition of NH3 into H2 with the heat from (low ignition temperature) NH3 , and the purification of NH3 through oxidation.

"Our catalyst appears to be a step in the right direction to fight anthropogenic since it does not emit greenhouse gasses like CO2 and should improve the sophistication of within our society," said study leader Dr. Satoshi Hinokuma of IROAST. "We are planning to conduct further research and development under more practical conditions in the future."

This research was posted online in the Journal of Catalysis on 26 March 2018.

Explore further: Catalyst for the carbon-free production of hydrogen gas from ammonia

More information: Satoshi Hinokuma et al, Catalytic ammonia combustion properties and operando characterization of copper oxides supported on aluminum silicates and silicon oxides, Journal of Catalysis (2018). DOI: 10.1016/j.jcat.2018.03.008

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Tenstats
not rated yet Apr 30, 2018
Once again there is a complete breakage between research and reality. First of all, ammonia doesn't crow on trees. It is synthesized using notrogen and hydrogen. Hydrogen generated from shift reaction: water + carbon (natural gas) to generate CO and H2. Thereis an energy penalty associated with this, and the splitting reaction generates CO + H2. OK, now the formation of NH3 from N2 and H2 requires energy (think of heat of formation of ammonia). This requires an energy input. So, two parts of the process require an energt input: Generating H2 and synthesizing ammonia, and you only get out one energy output. Overall, ammonia combustion is an energy consuming process. Any research like this should supply the overall energy balance, and not just saying "assume we have a supply of ammonia".
Also, ammonia is toxic. I was a project manager for an air pollution project for two power plants where we supplied liquid anhydrous ammonia storage and vaporization systems.

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