MADRID, 3 ago. (EUROPE PRESS) – Brazilian researchers have successfully converted methane to methanol using light and the diffusion of transition metals such as copper in a process called photooxidation.
According to an article about the study published in Chemical Communicationsit was the best reaction found so far to convert methane gas into a liquid fuel under ambient conditions of temperature and pressure (25 °C and 1 bar, respectively).
The results of the study are an important step towards making natural gas available as an energy source to produce alternative fuels other than gasoline and diesel. Although natural gas is considered a fossil fuelits conversion to methanol emits less carbon dioxide (CO2) than other liquid fuels in the same category.
In Brazil, methanol plays a central role in the production of biodiesel and in the chemical industry, who use it to synthesize many products.
Additionally, capturing methane from the atmosphere is critical to mitigating the adverse effects of climate change. because the gas has 25 times the potential of CO2, for example, to contribute to global warming.
“There is much debate in the scientific community about the extent of the planet’s methane reserves. According to some estimates, they may have twice the energy potential of all other fossil fuels combined. As we transition to renewable energy, we will have to use all this methane at some point“, Marcos da Silva, first author of the article, said the Agência FAPESP. Silva is a PhD student at the Department of Physics at the Federal University of São Carlos (UFSCar).
According to Ivo Freitas Teixeira, professor at UFSCar, Silva’s thesis advisor and last author of the article, the photocatalyst used in the study was an important innovation. “Our group made a significant innovation by oxidizing methane in a single step“, he said. “In the chemical industry, this conversion takes place through the production of hydrogen and CO2 in at least two stages and under very high temperature and pressure conditions. Our success in obtaining methanol under mild conditions, using less energy, is a major step forward.“.
According to Teixeira, the results pave the way for future research on the use of solar energy for this conversion process, which could further reduce its impact on the environment.
In the laboratory, the scientists synthesized crystalline carbon nitride in the form of polyheptazine imide (PHI), using non-noble or earth-abundant transition metals, especially copper, to produce visible light active photocatalysts.
They then used the photocatalysts in methane oxidation reactions with hydrogen peroxide as a promoter. The copper-PHI catalyst generated large amounts of liquid oxygenation products, especially methanol (2,900 micromoles per gram of material in four hours).
“We found the best catalyst and other necessary conditions for the chemical reaction, for example using a large amount of water and only a small amount of hydrogen peroxide, which is an oxidizing agent,” said Teixeira. “The next steps include gaining a greater understanding of the active copper sites in the material and their role in the reaction. We also plan to use oxygen directly to produce hydrogen peroxide in the reaction itself. If successful, this should make the process safer and more economically viable.”
Another point that the group will continue to investigate is related to copper. “We work with dispersed copper. When we wrote the paper, we did not know if we were dealing with isolated atoms or clusters. Now we know they are cumulus“, he explained.
In the study, the scientists used pure methane, but in the future they will extract the gas from renewable sources such as biomass. According to the United Nations, methane has so far been responsible for about 30% of global warming since the pre-industrial era. Methane emissions from human activity be reduced by up to 45% over the next ten years, avoiding a rise of almost 0.3°C by 2045.
The strategy of converting methane to liquid fuel using a photocatalyst is new and not commercially available, but its short-term potential is significant. “We started our research more than four years ago. We now have much better results than what Professor Hutchings and his group did in 2017, which inspired our own research,” said Teixeira, referring to a study published in the journal Science by researchers affiliated with him. universities in the United States and the United Kingdom, and directed by Graham Hutchings, professor at Cardiff University.
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