A modified indium oxide catalyst developed by researchers at ETH Zurich, Switzerland, with sponsorship from Total, La Défense, France, efficiently converts carbon dioxide and hydrogen directly into methanol. It offers an attractive option for green production of methanol, they say.
The efficacy of indium oxide in this role originally was demonstrated by ETH Zurich professor of catalysis engineering Javier Pérez-Ramírez and his team in 2016. At that time, the researchers reported high activity, 100% selectivity and “remarkable” stability for 1,000 hours using indium oxide supported on zirconium dioxide under industrially relevant conditions. However, further work revealed the catalyst’s level of activity necessitated quantities of indium oxide that precluded industrial viability.
Now, the team has come up with a new approach that involves treating the indium oxide with a small quantity of palladium, a known hydrogen gas splitter.
After investigating different treatments, including coating the catalyst with palladium, the scientists discovered that introducing palladium into the indium oxide crystal lattice structure aided the formation of palladium clusters on the lattice surface. These, in turn, gave the best conversion results: space-time yield (STY) started at 1.01 g methanol/hr/g catalyst and still remained at 0.96 g/hr/g after 500 hours onstream. More details appear in a recent article in Nature Communications.
The methanol STY, say the researchers, is 15% higher than that achieved by the best performer reported previously. Moreover, residence time is roughly 60% shorter, enabling a 60% reduction in reactor size, which is a strong plus for prospective industrial processes, they note.
Figure 1. Synthesis spurred by new catalyst enables recycling carbon dioxide and hydrogen. Source: ETH Zurich/Matthias Frei.
The boost in catalyst activity doesn’t incur adverse effects on either selectivity or stability, the researchers add.
Unlike other methods currently under development to produce green fuels, the technology has the great advantage that it’s almost ready for the market, says Pérez-Ramírez. All it needs is a supply of carbon dioxide and hydrogen from renewable sources.
ETH Zurich and Total jointly have filed a patent on the technology. Total now plans to scale up the approach and potentially implement the technology in a demonstration unit over the next few years. While the investment and timescale for the project remain confidential, Pérez-Ramírez notes the unit likely will be located at a Total facility.
“Now we are starting to look into designing catalysts that operate as efficiently as the one reported, but at a significantly lower pressure. This is a challenge, but it will reduce the energy consumption of the process due to lower compression costs,” he notes.