A group of researchers managed to convert methane into methanol using light and dispersed transition metals such as copper in a process known as photooxidation. According to a research paper published in the Chemical communications reaction was the best obtained to date for the conversion of gaseous methane to liquid fuel at ambient temperature and pressure (25 °C and 1 bar, respectively).
The term bar as a unit of pressure comes from the Greek word for weight (baros). One bar is equivalent to 100,000 Pascals (100 kPa), which is very close to standard atmospheric pressure at sea level (101,325 Pa).
The results of the study are an important step in ensuring the availability of natural gas as an energy source for the production of fuels, alternative gasoline and diesel. Although natural gas considered a fossil fuel, less carbon dioxide (CO 2) than other liquid fuels in the same category.
In Brazil, methanol plays a key role in production of biodiesel and in chemical industry which uses it to synthesize many products.
In addition, methane Atmospheric capture is critical to mitigating climate change, as the gas’s potential is 25 times that of CO 2 for example, contribute to global warming.
“There is great debate in the scientific community about the size of the planet’s methane reserves. Some estimates suggest that they may have twice the energy potential of all other fossil fuels combined. In the transition to renewable energy, we will have to use all of this methane at some point. Marcos da Silva, the first author of the paper, told FAPESP. Silva is a Ph.D. candidate at the Department of Physics, Federal University of San Carlos (UFSCar).
The photocatalyst used in the study was a key innovation, according to Yves Freitas Teixeira, UFSCar professor, Silva’s thesis supervisor and last author of the paper. “Our group has made a significant innovation by oxidizing methane in one step,” he said. “In the chemical industry, this conversion occurs through the production of hydrogen and CO 2 in at least two stages and under conditions of very high temperature and pressure. Our success in producing methanol under mild conditions while using less energy is an important step forward.”
According to Teixeira, the findings pave the way for future research into harnessing solar energy for this conversion process, potentially further reducing its environmental impact.
Photocatalysts
In the laboratory, scientists have synthesized crystalline carbon nitride in the form of polyheptazinimide (PHI) using non-noble or earth-rich transition metals especially copper, to obtain active visible light photocatalysts.
They then used the photocatalysts in methane oxidation reactions with hydrogen peroxide as an initiator. The copper-PHI catalyst produced a large volume of oxygenated liquid products, especially methanol (2900 micromoles per gram of material, or μmol.g-1 in four hours).
“We discovered a better catalyst and other conditions needed for the chemical reaction, such as using a lot of water and only a small amount of hydrogen peroxide, which is an oxidizing agent,” Teixeira said. “Next steps include 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 even safer and economically viable.”
Another point the group will continue to investigate concerns copper. “We work with dispersed copper. When we wrote the paper, we did not know whether we were dealing with isolated atoms or clusters. Now we know that these are clusters,” he explained.
In the study, the scientists used pure methane, but in the future they will extract the gas from renewable energy sources such as biomass. Since the pre-industrial era, methane has been responsible for about 30% of global warming, according to the United Nations. Human-caused methane emissions could be cut by 45% over the next decade, avoiding a temperature rise of almost 0.3°C by 2045.
Methane conversion strategy to liquid fuel using a photocatalyst new and not commercially available, but its near-term potential is significant. “We started our research more than four years ago. We now have much better results than Professor Hutchings and his group in 2017, which motivated our own research,” said Teixeira, referring to the study. published in the magazine Science researchers associated with universities in the United States and Great Britain, led by Graham Hutchings, a professor at Cardiff University in Wales.
Additional information:
Marcos AR da Silva et al. Selective photooxidation of methane to methanol under mild conditions, facilitated by highly dispersed Cu atoms on crystalline carbon nitrides, Chemical communications (2022). DOI: 10.1039/D2CC01757A
Citation: Scientists reveal method to turn methane gas into liquid methanol (2 August 2022) retrieved 2 August 2022 from https://phys.org/news/2022-08-scientists-reveal-method-methane-gas.html
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