Scientists have discovered a clean, low-cost way to convert carbon dioxide into methanol, a key ingredient in the production of plastics, adhesives and solvents, and a promising fuel for transportation.
Scientists from Stanford University, SLAC National Accelerator Laboratory in the US and the Technical University of Denmark identified a new nickel-gallium catalyst that converts hydrogen and carbon dioxide into methanol with fewer side-products than the conventional catalyst.
"Methanol is processed in huge factories at very high pressures using hydrogen, carbon dioxide and carbon monoxide from natural gas," said study lead author Felix Studt, a staff scientist at SLAC.
"We are looking for materials than can make methanol from clean sources under low-pressure conditions, while generating low amounts of carbon monoxide," Studt said.
"Imagine if you could synthesise methanol using hydrogen from renewable sources, such as water split by sunlight, and carbon dioxide captured from power plants and other industrial smokestacks," said co-author Jens Norskov, a professor of chemical engineering at Stanford.
"Eventually we would also like to make higher alcohols, such as ethanol and propanol, which, unlike methanol, can be directly added to gasoline today," Norskov said.
Worldwide, about 65 million metric tons of methanol are produced each year for use in the manufacture of paints, polymers, glues and other products.
In a typical methanol plant, natural gas and water are converted to synthesis gas ("syngas"), which consists of carbon monoxide, carbon dioxide and hydrogen.
The syngas is then converted into methanol in a high-pressure process using a catalyst made of copper, zinc and aluminum.
Scientists identified the active sites on the copper-zinc-aluminum catalyst that synthesise methanol.
Studt then searched for promising catalysts in a computerised database that he and co-author Frank Abild-Pedersen developed at SLAC.
Studt compared the copper-zinc-aluminum catalyst with thousands of other materials in the database. The most promising candidate turned out to be a little-known compound called nickel-gallium.
Norskov turned to a research group at the Technical University of Denmark led by co-author Ib Chorkendorff. First, the Danish team carried out the task of synthesising nickel and gallium into a solid catalyst.
Then the scientists conducted a series of experiments to see if the new catalyst could actually produce methanol at ordinary room pressure.
At high temperatures, nickel-gallium produced more methanol than the conventional copper-zinc-aluminum catalyst, and considerably less of the carbon monoxide byproduct.
The results are published in the journal Nature Chemistry.
