Researchers from the US and Denmark have identified a new, nickel-gallium cat- alyst that turns hydrogen and carbon dioxide into methanol while producing fewer byproducts than the current catalyst. This new approach is low-cost and much cleaner that the existing process. The research is a joint project between Stanford University, the SLAC National Accelerator Laboratory (SLAC originally stood for Stanford Linear Accelerator Centre) and the Danish Technical University (DTU).

Methanol is a very important input for the manufacture of adhesives, solvents and plastics and could be a fuel for the trans- port sector in the future. “Metha-nol is processed in huge factories at very high pressures using hydrogen, carbon dioxide and carbon monoxide from natural gas,” explained SLAC staff scientist (and study lead author) Dr Felix Studt. “We are looking for materials than can make methanol from clean sources under low-pressure conditions, while generating low amounts of carbon monoxide.”

The current catalyst for the industrial production of methanol is composed of copper, zinc and aluminium. Some 65-million tons of methanol is made every year. Typically, in an industrial plant, natural gas and water are turned into synthesis gas consisting of carbon dioxide, carbon monoxide and hydrogen. This synthesis gas is transformed into methanol through a high- pressure process employing the copper-zinc-aluminium catalyst.

“We spent a lot of time studying methanol synthesis and the industrial process,” he reported. “It took us about three years to figure out how the process works and to identify the active sites on the copper-zinc-aluminium catalyst that synthesise methanol.” Having comprehended the synthesis process at molecular level, the team set out to identify a new catalyst that would do the same job, but at low pressures and employing just hydrogen and carbon dioxide. They did this by searching through a huge computerised database at SLAC that had been developed by Studt and co-researcher Dr Frank Abild-Pedersen.

This data search, which is known as computational materials design, identifies possible new functional materials using only computer calculations. There is no potentially time- (and money-) consuming trial-and-error labo- ratory work to try to find such materials. “You use your insight and enormous computer power to identify new and interesting materials, which can then be tested experimentally,” elucidated Sustainable Energy for Catalysis Centre (Suncat) for Interface Science and Catalysis director and Stanford chemical engineering professor Jens Nørskov.

Through this process, the copper-zinc-aluminium catalyst was compared with thousands of other compounds. The most promising alternative was identified as nickel-gallium. “Once we got the name of the compound out of the computer, someone still had to test it,” noted Nørskov. “We don’t do experiments [at Suncat], so we have to have a good experi- mental partner.” That partner is DTU. There, a team headed by Centre for Individual Nano-particle Functionality director Professor Ib Chorkendorff synthesised the nickel and gallium into a solid catalyst. Then they ran experiments to ascertain if this catalyst could make methanol at normal room pressure. It could. In fact, at high temperatures, the nickel-gallium catalyst produced more methanol with less carbon dioxide by-product than the copper-zinc-aluminium catalyst.

“You want to make methanol, not carbon dioxide,” pointed out Chorkendorff. “You also want a catalyst that’s stable and doesn’t decompose. The lab tests showed that nickel-gallium is, in fact, a very stable solid. We’d like to make the catalyst a little more clean. If it contains just a few nanoparticles of pure nickel, the output drops quite a bit, because pure nickel is lousy at synthesising methanol. In fact, it makes all sorts of chemical by-products that you don’t want.”

A lot of work remains to be done on the new catalyst. With nickel relatively abundant and gallium widely used in electronics, it is possible that the new process could be expanded to an industrial scale.