New Catalyst Converts CO2, Methanol, and Hydrogen to Ethanol Cheaply

An international collaboration of researchers has introduced a novel homogeneous catalytic process designed to convert methanol, carbon dioxide, and hydrogen into ethanol. This development utilizes inexpensive and stable catalyst precursors, overcoming a significant hurdle in transforming captured carbon dioxide into valuable chemical products. Existing methods often rely on costly or intricate catalyst components that are difficult to implement on an industrial scale.

The study, involving institutions from the UK and China, reports the design of a catalytic system employing commercially available ruthenium chloride hydrate and cobalt chloride hexahydrate. Following activation with carbon monoxide, the catalyst efficiently produces ethanol from the feedstocks under relatively mild conditions, specifically at 170°C (338°F).

Under optimized conditions, the catalyst demonstrated a high ethanol selectivity of 64.9% and a space-time yield of 3.9 g L⁻¹ h⁻¹, surpassing the performance of previously reported ruthenium-cobalt catalyst systems for this reaction. Researchers highlighted the practical advantages of this new system, including ease of storage, recyclability, and potential for large-scale application.

The team also elucidated the reaction mechanism, revealing that carbon dioxide is initially converted to carbon monoxide via a reverse water gas shift reaction, with the carbon monoxide then serving as an intermediate in ethanol formation. Ruthenium and cobalt are observed to play complementary roles, with ruthenium facilitating hydrogenation and cobalt promoting the carbon-carbon bond formation necessary for ethanol synthesis. The activated catalyst exhibited stability during storage and maintained good activity after five recycling cycles, with preliminary scale-up studies in a 3 L reactor showing sustained high activity and selectivity.