Material Prospective for the Green Development of Hydrocarbon Energy

12:28, January 21, 2022

It will reduce the environmental damage caused by burning fossil fuels

Researchers at the Institute of Solid State Chemistry of the Ural Branch of the Russian Academy of Sciences and the Ural Federal University have discovered a new substance for use in the latest environmentally friendly technology for burning fossil fuels. This technology allows, while remaining within the framework of hydrocarbon energy, to significantly reduce the load on the environment. The researchers published an article about their work in Materials Research Bulletin.

It is about the technology of chemical cycling with oxygen accumulation - the so-called CLOU-processes (chemical looping with oxygen uncoupling). Compared to conventional combustion technologies at thermal power plants, their undeniable advantage is that the oxygen comes not from the air, but from solid oxides of transition metals. In this case, the combustion products are easily separated, and the carbon dioxide generated during the combustion of hydrocarbons is utilized by pumping it into storage tanks or sent for industrial purposes.

The properties necessary for CLOU-processes oxides are able to accumulate a significant amount of molecular oxygen at a high rate, up to 20% of their own mass, then release it and then regenerate, keeping their chemical composition unchanged in the oxidation/reduction cycles. In this case, fuel combustion can be carried out without losses for a long time.

CLOU processes are a new word in science and technology, and the scientific world is busy looking for suitable oxide materials. A group of scientists investigated cobalt-modified praseodymium-barium manganite (PrBaMn2O6) as such.

"It is known that at elevated temperatures manganites can actively exchange oxygen with the environment, being in direct contact with hydrocarbons. Imagine a sponge that first absorbs a large amount of water and then, when compressed, releases it back. In CLOU processes, essentially the same thing happens: manganites play the role of a sponge, releasing large amounts of oxygen in combustion reactions, and then absorbing it back when interacting with air. However, the original (unmodified) manganite gradually degrades when saturated with oxygen, so its oxygen capacity decreases. Our group found that the introduction of cobalt atoms in the oxide PrBaMn2O6 stabilizes its structure, it remains when the temperature and composition of the gas environment," explains the choice of research leader and co-author of Aleksey Suntsov, leading researcher of the Institute of Solid State Chemistry, associate professor of the Institute of New Materials and Technologies UrFU.

In other words, this material is destroyed neither by oxidation nor reduction. On this basis, chemists first suggested that it could be suitable for use in CLOU-processes, and tested their hypothesis.

Scientists have studied in detail the fundamental and functional characteristics of cobalt-modified manganite. Using mathematical modeling methods supported by corresponding experimental results, the authors showed that oxygen is released from the oxide unevenly. As it turned out, the addition of cobalt activates some areas of the material, making it much easier for oxygen to escape.

"By replacing some of the manganese atoms with cobalt, we increased the total amount of oxygen in the oxide that is available for rapid release during hydrocarbon combustion. This resulted in a record-breaking increase in the oxygen capacity of the material, the volume, and the rate of oxygen release compared to the original manganite. Thus, we received confirmation that the investigated compositions have excellent prospects for use in CLOU-processes. Moreover, the work performed and the results obtained are important for the design of new materials: there is an understanding of how to modify their chemical composition in a targeted way to increase the oxygen capacity and oxygen exchange rate," comments Aleksey Suntsov.

This research project was supported by the Russian Science Foundation (grant № 19-79-10147).

Reference

Traditionally, combustion of hydrocarbons - natural gas, fuel oil and coal - in thermal power plants uses air as an oxidizer. However, three quarters of it consists of nitrogen, which forms toxic oxides as a result of combustion processes - they, in turn, concentrate in the reaction products together with carbon dioxide. The resulting mixture is poorly separable and is often simply released into the atmosphere. By accumulating there, additional amounts of carbon dioxide exacerbate the greenhouse effect and provoke further global warming. This is especially dangerous in connection with the continuous increase of humanity's energy consumption due to the explosive growth of the planet's population and the dramatic increase in the standard of living. At the same time, thermal power plants provide more than 60% of the world's electricity production, and their contribution to humanity's energy supply will not change much in the coming years. The share of organic fuel - the main pollutant of the biosphere - is more than 90% in heat and energy generation.

The technology of chemical cycling with oxygen accumulation (CLOU-processes) is a promising environmentally friendly alternative to the traditional methods of combustion of hydrocarbon fuels.

The news article was translated by UrFU International Marketing Office
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