Sustainable Production of Dialkoxymethane Ethers and Related Acetals Using CO2, H2 and Alcohols or Diols

Dialkoxymethane (DAM) ethers, so-called oxymethylene ethers (OMEs), are compounds constituted by a CH2-unit bound to two identical alkoxy substituents. These compounds have showcased interesting technological applications as fuel additives or fuels, as a consequence of their interesting properties such as their low vapor pressure, high viscosity, cetane number and oxygen content. Moreover, they are also employed as environmentally-benign solvents and bulk compounds useful in fine-chemical industry. In addition, DAM ethers are considered formaldehyde surrogates. Industrially, dimethoxymethane (DMM) is still produced via two-step protocol involving toxic formaldehyde that consists of a first step of methanol oxidation (Formox process). Hence, the development of more sustainable protocols for their synthesis is highly desired. Among the different strategies reported for DAM synthesis, its production from CO2/H2 and alcohols constitutes a practical, green and attractive alternative route. In this concept, a careful discussion of the developed catalytic protocols for synthesizing DAM from CO2/H2 or formic acid/H2 and alcohols/diols will be summarized. A special emphasis will be performed on the reaction mechanisms involved and the catalyst nature design and characterization.