Gornay, J; Secordel, X; Capron, M; Tesquet, G; Fongarland, P; Payen, E; Dubois, JL; Dumeignil, F
Direct Synthesis of 1,1-dimethoxymethane from Methanol by Minor Modification of the Formaldehyde Production Process over FeMo Catalysts - The partial oxidation reaction of methanol over redox catalysts mainly leads to the formation of formaldehyde. Over optimized FeMo-based catalysts, small quantities of products like formic acid or COx are also detected. When the catalysts have also acidic properties, condensation/dehydration reactions take place in addition to the consecutive oxidation reactions, which leads to the formation of 1,1-dimethoxymethane (DMM or methylal), dimethylether and methyl formate. Among the aforementioned products, DMM is especially interesting for industrial applications owing to its good physical properties (very good solvent, low viscosity, low superficial pressure, etc.). The main industrial applications are a use as a green solvent or a chemical intermediate; it is further suitable as a fuel additive in replacement of the petro-chemistry-derived products. At the industrial scale, DMM is conventionally produced in two steps:
- formaldehyde synthesis followed by;
- reaction between formaldehyde and methanol over an acid catalyst to finally obtain DMM.
However, in order to reduce the DMM production costs, the development of a catalyst and of the associated process enabling the direct conversion of methanol to DMM are necessary. As aforementioned, over a FeMo-based catalyst, the main product obtained by methanol partial oxidation is formaldehyde. This process is carried out at a low methanol partial pressure, the rich methanol composition area - over the explosivity zone - being not industrially operated. Using a rich methanol composition, we observed over the same FeMo-based catalyst, the best productivity ever reported in the literature (4.6 kg(DMM).h(-1).kg(Cat)(-1) at 553 K at a methanol conversion of 56% and a DMM selectivity of 90%). This opens interesting perspectives for converting formaldehyde production units (FeMo catalyst in multitubular reactor) into DMM production units by almost only changing the methanol partial pressure in the feed, while working in air as a diluting agent/oxidant.