CO2 hydrogenation into dimethyl ether

Dimethyl ether (DME) has been identified as a key feedstock for organic synthesis as well as an environmentally friendly fuel, with low associated emissions of pollutants. It is conventionally obtained from syngas in a two-step process, involving first methanol synthesis in presence of a metal-oxide catalyst, followed by its dehydration over an acidic system. Considering the significant carbon footprint of the whole process chain, there is a growing interest to deliver an innovative one-step process to DME via CO₂ conversion in presence of green hydrogen. Unfortunately, because of the relatively low reactivity of CO₂, high reaction temperatures and pressures are typically required. Yet, to enhance the rate of CO₂ activation, bifunctional or hybrid catalysts need to be properly designed and developed, by realizing an optimal distribution of active sites of different nature suitable to deliver an efficient catalytic process for the direct production of DME. This chapter highlights the basic features of the innovative catalytic one-step route to DME in comparison to the conventional two-step process, providing a general assessment in terms of thermodynamics, activity-selectivity pattern of the most promising catalytic systems as well as the main reactor configurations, overall determining the process economics.