A group of researchers has succeeded in converting methane to methanol using light and dispersed transition metals such as copper in a process known as photo-oxidation. according to a Article Reporting of the study published in chemical communication The reaction was the best ever to convert methane gas to liquid fuel under ambient conditions of temperature and pressure (25 °C and 1 bar, respectively).
The word bar as a unit of pressure is derived from the Greek word weight (baros). A bar is equal to 100,000 pascals (100 kPa), which is very close to the standard atmospheric pressure (101,325 Pa) at sea level.
The study results are an important step towards making natural gas available as an energy source for the production of alternative fuels to gasoline and diesel. Although natural gas is considered a fossil fuel, its conversion to methanol emits less carbon dioxide (CO2) than other liquid fuels in the same category.
In Brazil, methanol plays an important role in biodiesel production and the chemical industry, which uses it to synthesize many products.
In addition, the capture of methane from the atmosphere is important for mitigating the adverse effects of climate change, as the gas has 25 times the potential of CO2, for example, to contribute to global warming.
“There is a great debate in the scientific community about the size of the planet’s methane reserves. By some estimates, they may have twice the energy potential of all other fossil fuels combined. In the transition to renewables, we must at some point All of this methane has to be tapped into,” Marcos da Silva, the article’s first author, told Agenesia FAPESP. Silva is a PhD candidate at the Department of Physics of the Federal University of So Carlos (UFSCar).
The study was supported by FAPESP through two projects (20/14741-6 And 21/11162-8), by the Council of Higher Research (CAPES, an agency of the Ministry of Education), and the National Council for Scientific and Technological Development (CNPQ, a branch of the Ministry of Science, Technology and Innovation).
According to Evo Freitas Teixeira, professor at UFSCar, thesis advisor to Silva and eventual author of the article, the photocatalyst used in the study was a significant innovation. “Our group innovated significantly by oxidizing methane in a single step,” he said. “In the chemical industry, this conversion occurs through the production of hydrogen and CO2 in at least two steps and under very high temperature and pressure conditions. Our success in obtaining methanol under mild conditions while expending less energy is a major factor.” step.”
According to Teixeira, the results pave the way for future research into the use of solar energy for this conversion process, potentially reducing its environmental impact even further.
light trigger
In the laboratory, scientists synthesized crystalline carbon nitride in the form of polyheptazine imide (PHI), using non-noble or Earth-abundant transition metals, particularly copper, to produce active visible-light photocatalysts.
They then used the photocatalyst in methane oxidation reactions with hydrogen peroxide as an initiator. The copper–PHI catalyst generated large amounts of oxygenated liquid products, especially methanol (2,900 micromol per gram of the material, or μmol.g–1 in four hours).
“We discovered the best catalyst and other conditions needed for the chemical reaction, such as using large amounts of water and only small amounts of hydrogen peroxide, which is an oxidizing agent,” Teixeira said. “Next steps include understanding more about the sites of active copper 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.” If so, it should make the process more secure and economically viable.”
Another point that the group will continue to investigate relates to copper. “We work with scattered copper. When we wrote the article, we didn’t know whether we were dealing with isolated atoms or clusters. Now we know they are clusters,” he explained.
In the study, the scientists used pure methane, but in the future they will extract the gas from renewable energy such as biomass.
According to the United Nations, since the pre-industrial era, methane has now caused about 30% of global warming. Methane emissions from human activity could be reduced by 45% in the coming decade, avoiding an increase of about 0.3 °C by 2045.
The strategy for converting methane to liquid fuel using photocatalysts is new and not commercially available, but its potential is significant in the near future. “We started our research four years ago. We now have far better results than those of Professor Hutchings and his group in 2017, which inspired our own research,” Teixeira said, referring to a study published in the magazine science by researchers affiliated with universities in the United States and the United Kingdom, and led by Professor Graham Hutchings from Cardiff University in Wales.
Reference: Silva March DA, Gil JC, Tarquina NV, et al. Selective methane photooxidation in methanol under mild conditions promoted by highly dispersed Cu atoms on crystalline carbon nitride. chem commune, 2022;58(53):7419-7422. doi: 10.1039/d2cc01757a