From CO2 to DME: catalytic advances, challenges, and alternatives to conventional gas-phase routes

Dimethyl ether (DME) is gaining attention as both a biofuel and electro-fuel (e-fuel) due to its high volumetric energy density (0.16 kg H₂ per l) and rich hydrogen content, making it a promising energy carrier. Global DME production is around 10 million tons annually, primarily derived from synthesis gas. This process typically requires high temperatures above 250 °C and elevated pressures, involving two catalysts and multiple stages of separation and distillation. A major breakthrough in DME production would involve utilizing CO₂ and H₂ mixtures under milder conditions in a single-step process. Such advancements could create a circular DME synthesis–consumption cycle, leading to significant reductions in greenhouse gas (GHG) emissions. This work explores recent developments in both direct and indirect DME production methods, with a focus on enhancing CO₂-to-DME processes. It highlights the design of highly active, durable, and selective catalysts, as well as scalable synthesis methods that eliminate expensive separation and distillation steps. In addition to conventional gas-phase approaches, this review presents a novel liquid-phase DME production pathway via methyl formate (MF), discussing its potential advantages and current limitations, particularly related to low conversion rates.