The use of natural gas as a chemical feedstock in the production of polymers, fuels, speciality chemicals and pharmaceuticals may become much easier, following the discovery of a new catalyst to convert it into a base product widely used across industry.
The lead researcher, Prof. Javier Pérez-Ramírez, described the process, saying, “We take a molecule of the natural gas constituent methane (CH4) and replace one of its hydrogen atoms with a bromine atom to form methyl bromide (CH3Br).The latter can be used as a base material in the chemical industry for the production of fuels and a range of chemicals, such as polymers and pharmaceuticals.”
The research team from the Swiss Federal Institute of Technology (ETH) have reported their discovery in the journal Nature, which defined the process as, “An attractive oxybromination method for the one-step functionalization of methane under mild conditions that integrates gas-phase alkane bromination with heterogeneously catalysed HBr oxidation, a step that is usually executed separately. Among many investigated material families, vanadium phosphate (VPO) is identified as the best oxybromination catalyst, as it provides selectivity for CH3Br up to 95% and stable operation for over 100 hours on stream.”
Whilst previous chemical processes have used the oxybromination of methane via catalysts to convert natural gas to into base materials for use in industry, they release large quantities of waste products. However, by using vanadium phosphate as a catalyst the bromine can be reused. As Pérez-Ramírez explains, “The beauty of our reaction is that it enables the bromine from hydrogen bromide to be embedded back into methyl bromide, using oxygen. In this way, the bromine cycle is closed, and no bromine is lost.”
The online journal Phys.org, explained the advantages of vanadium phosphate as, “Vanadium phosphate is a relatively mild oxidising catalyst, and this is exactly what chemists are seeking in the oxybromination of methane. On the one hand, the catalyst is sufficiently strong to allow hydrogen bromide to react with oxygen at the catalyst’s surface. On the other hand, the catalytic action of vanadium phosphate is too weak to oxidise the unwanted methane and the brominated reaction products.”
Vladimir Paunović, a doctoral student in Pérez-Ramírez’s team, further described the effectiveness of the new catalyst to ETH’s in-house reporter Fabio Bergamin. Saying, “Our method makes it possible to brominate methane in a single step at atmospheric pressure and at temperatures below 500 degrees Celsius. This makes it an attractive route for industry.” He continued by explaining how the new process is based on a stable a reaction. “This is because bromine is a halogen. Halogens react very readily with methane, which is desirable in this case, but they also attack the catalyst. Our catalyst resists the corrosive reaction environment, which is essential for its potential industrial application.”
The research is even more significant given the discovery of a large number natural gas fields in recent years. As more and more of these fields are tapped, the need for a more efficient method to process the natural gas extracted into base feedstock for use in the chemical industry will become more prominent.
As Ramirez himself points out, “We are currently experiencing a boom in natural gas exploration. If you include unconventional, hard to access reservoirs, such as shale gas or coal bed methane, estimates indicate that gas deposits will last for at least 100 years.”
If those estimates are accurate, and with the discovery of vanadium phosphate as an efficient catalyst, will the chemical industry of the future be able to stop worrying about the price of oil?
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