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Storing Hydrogen in Powder Form: An Important Step Toward a Greener Petrochemical Industry

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Hydrogen is increasingly presented as a sustainable solution for the energy transition. However, today 95% of hydrogen is produced from hydrocarbons (oil, natural gas and coal), which is the least expensive solution, but the most energy intensive. In addition, finding a material capable of storing a huge amount of gas for practical applications remains a major challenge. Recently, Australian researchers have discovered a new way to safely separate, store and transport large volumes of gas in powder form without waste, allowing the widespread use of hydrogen energy.

Hydrogen, used since the 19th century to power urban lighting networks and later to propel the Ariane rocket, has been used in industry for decades, where it has been used, among others, as a base material for the production of ammonia and methanol, as well as for refining petroleum products. , fuels and biofuels.

In addition, conventional refining methods use a high-energy “cryogenic distillation” process to separate crude oil into various gases, including hydrogen. This process accounts for 15% of global energy consumption, while global hydrogen consumption is less than 2%.

Thanks, in particular, to the advent of hydrogen fuel cells, the latter are becoming an energy vector that can contribute to the decarburization of certain industries, the provision of energy storage and the supply of electricity to buildings or the transport sector. However, the introduction of hydrogen technologies involves overcoming a number of obstacles, mainly related to the storage and transportation with full safety and efficiency of quite significant volumes of gas.

Indeed, this gas is very light, flammable, odorless and colorless. It mixes well with air, so explosive mixtures are easily formed. Heat may also cause violent fire or explosion.

Recently, nanotechnology researchers at the Institute for Frontier Materials (IFM) at Deakin University (Australia) claimed to have made a major breakthrough in gas separation and storage. Their discovery could drastically reduce the energy consumption of the petrochemical industry, as well as make storing and transporting hydrogen in powder form much easier and safer. Their results are published in Materials Today and their method is patent pending.

Mechanochemical revolution in hydrogen production and storage

Professor Chen, Chair of Nanotechnology at IFM, outlines the background of the study in a statement: “Australia is currently experiencing an unprecedented gas crisis and urgently needs a solution. More efficient use of cleaner gaseous fuels such as hydrogen is an alternative approach to reducing carbon emissions and slowing global warming.”

Currently, hydrogen and other gases are mainly produced by cryogenic distillation. This method is performed on liquefied gas obtained by rapidly compressing and decompressing the latter, which causes it to cool and liquefy. By gradually heating this gas, which has become liquid, and adjusting the various boiling points, it is possible to separate its various components. However, this method is extremely energy intensive.

As part of this study, the researchers developed an energy-efficient and waste-free mechanochemical separation process. You should know that mechanochemistry is a branch of chemistry that studies the chemical behavior of materials under mechanical action, as opposed to, for example, heat or light.

The “special ingredient” in the process, as the authors call it, is boron nitride powder, which absorbs substances very well. In addition, boron nitride is classified as a Level 0 chemical that poses no hazard. Specifically, during the process, boron nitride powder is placed in a mill – a cylinder – with stainless steel balls and separated gases. As the cylinder rotates at higher and higher speeds, the collision of the balls with the powder and the wall of this chamber causes a special mechanochemical reaction, leading to the absorption of gas by the powder.

The second author, Dr. Mateti, explains: “Boron nitride powder can be used repeatedly to perform the same gas separation and storage process over and over again.” Thus, this process can be repeated to separate gases one by one, since each gas is absorbed at different grinding intensity, gas pressure and time period. In successive experiments, the authors were able to separate the combination of alkyne, olefin, and paraffin gases.

Infographic summarizing the gas separation process. © Deakin University

The gas absorption process by grinding requires 76.8 kJ/s to store and separate 1000 liters of gas. This is almost 90% less energy than the current separation process in the oil industry. Dr. Mateti says: “We were so surprised to see that this happened, but every time we got the same result, it was a “lightning moment”.

Store gas in a solid state without risk and loss

Once absorbed by the powder, the gas can be easily and safely transported and stored anywhere as boron nitride is safe and available in large quantities. Then, when gas is needed, the powder can simply be heated under vacuum to release the gas as is. In addition, some gases are released from powders at higher temperatures than others, providing a second way to separate gases if they are stored together. This breakthrough is the culmination of three decades of work by Professor Chen and his team. This can help in the creation of solid-state storage technologies for a number of gases, including hydrogen.

Professor Chen explains that the current way to store hydrogen is to either compress it to 700 bar – 7 liters of hydrogen can hold as much energy as 1 liter of gasoline; or by liquefying it for further compression at -253°C – 4 liters of liquid hydrogen is equivalent to 1 liter of gasoline. Both require a lot of energy as well as hazardous processes and chemicals.

He adds: “We show that there is a mechanochemical alternative using a ball mill to store gas in a nanomaterial at room temperature. It doesn’t require high pressures or low temperatures, so it will provide a much cheaper and safer way to develop innovations like hydrogen cars.”

Finally, the IFM team tested the process on a small scale, separating about two to three liters of material. But they are hoping for the support of the industry to launch a full-fledged pilot project. Not to mention they filed a provisional patent application for their process.

Professor Chen concludes: “We need to further test this method in industry to develop its practical application. To take this from the lab to a larger industrial scale, we need to make sure the process is more economical, efficient and faster than traditional gas separation and storage methods.” Thus, this scalable mechanochemical process has great potential as an industrial separation technique and can provide significant energy savings.

Materials Today

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