Apr 18 2016
A new and direct method to transform gaseous methane into liquid methanol has been discovered by chemists at ETH Zurich and the Paul Scherrer Institute. This new discovery provides industry with a new method of using the gas, rather than the current method of burning it off.
Large amounts of methane worldwide are currently simply burnt - here on an oil rig. (Photograph: Colourbox)
Methane is a cheap and abundant gas. Even though methane can be used as a suitable base material and energy source for the chemical industry, a major quantity of this gas is just burnt off globally especially in refineries and oil fields.
On satellite images of Earth at night, the Middle East is brightly illuminated. This is not because the region has an especially high number of large, brightly lit settlements, but rather because of methane flaring at the oil fields.
Jeroen van Bokhoven, Professor for Heterogeneous Catalysis, ETH Zurich
Converting gas into methanol in liquid form is currently not profitable, even though it is more reactive and easier to transport. This is one reason for a wasteful approach to methane. Currently on the industrial level this conversion is performed using an elaborate, indirect, and energy-intensive process that also involves the development of syngas as a midway step.
The stuff of many chemists’ dreams
Many chemists consider the easy, direct conversion of methane into methanol as a dream reaction.
Jeroen van Bokhoven, Professor for Heterogeneous Catalysis, ETH Zurich
Bokhoven and his team have demonstrated a new approach to this in a recent work. As a catalysis researcher, Bokhoven states that the global industrial field is also keen to use methane because it is an abundant and cost-effective gas. The increase in the global shale gas production results in an increase in the release of huge methane volumes.
On a theoretical level, it is possible to convert methane into methanol using crystalline, copper-containing silicon aluminum compounds (zeolites) as catalysts. The process is executed at different temperatures and is cyclical. Extremely high temperatures, often up to 450°C, are needed to activate the catalyst. However, it is not possible to carry out the exact reaction between methane and oxygen to develop methanol when the temperatures are over 200 degrees. Otherwise it will result in methanol burning. It is necessary to repeatedly heat and cool the reaction vessel. This is the reason why this approach has never found its way out of research laboratories and into industry.
High pressure instead of high temperatures
Presently, van Bokhoven and his team have illustrated the possibility of executing this reaction cycle at a constant temperature of 200 degrees. This was achieved by using methane at an extremely high pressure: 36 bars rather than below 1 bar, as earlier used.
Working at a constant temperature makes this a much easier process to implement in industry.
Patrick Tomkins, Master Student, ETH Zurich
The researchers used ray absorption spectroscopy, and demonstrated that at the atomic level, the catalyzed reaction obtained from the latest low-temperature/high-pressure method does not occur at the same position, like what happened in the existing high-temperature method.
As a result of the high pressure, different active centres are utilised in the copper zeolites.
Jeroen van Bokhoven, Professor for Heterogeneous Catalysis, ETH Zurich
van Bokhoven highlights that this new approach is still not ready for direct use in the industry due to insufficient yield for industrial purposes. Still, the approach makes room for a wide variety of possibilities.
In the past, catalysis scientists focused their research on copper zeolites for this reaction, because these are the most successful option in the high-temperature method. We also used these copper zeolites for the current study.
Jeroen van Bokhoven, Professor for Heterogeneous Catalysis, ETH Zurich
van Bokhoven states that it is worth examining varied catalysts as the high-pressure method is catalyzed in a different way at the atomic level. Catalysts that have not been considered until now can also be examined. There is the possibility that these catalysts can be more appropriate for the high-pressure method. van Bokhoven and his team will work on this area in their future research work as they focus on developing an efficient, direct and easy method to convert methane into methanol. This will be a dream come true for the global industry as well as for the scientific community.