Towards a Sustainable Synthesis of Oxymethylene Dimethyl Ether by Homogeneous Catalysis and Uptake of Molecular Formaldehyde

Abstract

Oxymethylene dimethyl ethers (OME ; CH (-OCH -) O-CH , n=3-5) are a novel class of sustainable synthetic fuels, which are of increasing interest due to their soot-free combustion. Herein a novel anhydrous OME synthesis route is presented. Catalyzed by trimethyloxonium salts, dimethoxymethane takes up monomeric gaseous formaldehyde instantaneously and forms high purity OME at temperatures of 25-30 °C. This new anhydrous approach using molecular formaldehyde and catalytic amounts of highly active trimethyloxonium salts represents a promising new step towards a sustainable formation of OME emanating from CO and H .

A Computational Investigation of OME‐synthesis through Homogeneous Acid Catalysis

“…The acid catalyzed formation of higher OMEs from OME1 and TOX has been investigated using ab initio and DFT calculations employing a protonated OME1 as a homogeneous catalyst that can be generated either by protonation with a Brønsted acid or by reaction of OME1 with a trimethyl oxonium cation. Based on our findings, we expect trimethyl oxonium salts to be an active precatalyst, in agreement with a recent experimental study . Once protonated OME1 is formed, we find both direct TOX incorporation and TOX‐decomposition to FA and subsequent FA‐incorporation to be viable reaction mechanisms for the formation of higher OMEs.…”

“…Experimentally, OME synthesis is carried out in solution typically using ambient to elevated temperatures and often pure reactants as solvent ,,,. We will study the reaction of OME1 and TOX without additional solvents at room temperature.…”

“…We will now study how likely this species is to be formed from a given precatalyst. The simplest way of doing this is to consider trimethyl oxonium salts as precatalysts that have also been used in a recent experimental study . Neglecting the effecting of the weakly‐coordinating counter‐ions, the trimethyl oxonium cation can methylate OME1, which by reaction with another OME1 forms A 11 and DME.…”

“…The simplest way of doing this is to consider trimethyl oxonium salts as precatalysts that have also been used in a recent experimental study. [8] Neglecting the effecting of the weakly-coordinating counterions, the trimethyl oxonium cation can methylate OME1, which by reaction with another OME1 forms A 11 and DME. This reaction sequence is shown in Figure 2 and is mildly uphill in free energy (30 kJ/mol) confirming that trimethyl oxonium salts are viable precatalysts for this reaction.…”

Utilization of Formic Acid as C1 Building Block for the Ruthenium‐Catalyzed Synthesis of Formaldehyde Surrogates

“…Additionally, a non‐precious and efficient cobalt‐triphos system could be established for this hydrogenation sequence of CO 2 to DMM . Moreover, new catalyst concepts and reaction pathways enlarged the synthetic portfolio and paved the way to unprecedented DMM synthesis approaches …”