(São Paulo Research Foundation/SciTech Daily) A team of researchers has successfully converted methane into methanol using light and scattered transition metals such as copper in a process known as photo-oxidation. The reaction was the best achieved to date for converting methane gas into liquid fuel at ambient temperature and pressure (25 °C and 1 bar, respectively), according to a study published in the journal Chemical Communications.
The term bar as a pressure unit comes from the Greek word meaning weight (baros). One bar equals 100,000 Pascals (100 kPa), close to the standard atmospheric pressure at sea level (101,325 Pa).
The study’s findings are a crucial step toward making natural gas accessible as a source of energy for the production of alternative fuels to gasoline and diesel. Despite the fact that natural gas is a fossil fuel, its conversion into methanol produces less carbon dioxide (CO2) than other liquid fuels in the same category.
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Methanol is vital in biodiesel production and the chemical industry in Brazil, where it is used to synthesize a variety of products.
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“Our group innovated significantly by oxidizing methane in a single stage,” he said. “In the chemical industry, this conversion occurs via 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, while also expending less energy, is a major step forward.”
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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 active visible-light photocatalysts.
They then used the photocatalysts in methane oxidation reactions with hydrogen peroxide as an initiator. The copper-PHI catalyst generated a large volume of oxygenated liquid products, especially methanol (2,900 micromoles per gram of material, or µmol.g-1 in four hours).
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Another point the group will continue to investigate relates to copper. “We work with dispersed copper. When we wrote the article, we didn’t know whether we were dealing with isolated atoms or clusters. We now know they’re clusters,” he explained.
In the study, the scientists used pure methane, but in the future, they will extract the gas from renewables such as biomass.READ MORE
“Selective methane photooxidation into methanol under mild conditions promoted by highly dispersed Cu atoms on crystalline carbon nitrides” by Marcos A. R. da Silva, Jéssica C. Gil, Nadezda V. Tarakina, Gelson T. S. T. Silva, José B. G. Filho, Klaus Krambrock, Markus Antonietti, Caue Ribeiro and Ivo F. Teixeira, 31 May 2022, Chemical Communications.
DOI: 10.1039/D2CC01757A
“Aqueous Au-Pd colloids catalyze selective CH oxidation to CH OH with O under mild conditions” by Nishtha Agarwal, Simon J. Freakley, Rebecca U. McVicker, Sultan M. Althahban, Nikolaos Dimitratos, Qian He, David J. Morgan, Robert L. Jenkins, David J. Willock, Stuart H. Taylor, Christopher J. Kiely and Graham J. Hutchings, 7 September 2017, Science