# Investigation of the cooperative-effects of Lewis- and Brønstedt acids in homogeneously catalyzed OME fuel synthesis by inline-NMR monitoring

## TL;DR

This study uses inline NMR to explore how combining Lewis and Brønsted acids affects the production of OME fuel from trioxane and dimethoxy methane.

## Contribution

The study reveals a cooperative effect between weak Lewis acids and Brønsted acids, optimizing reaction rates in OME synthesis.

## Key findings

- MgCl2, a weak Lewis acid, shows the highest catalytic activity in the synthesis.
- The optimal ratio of Lewis acid to Brønsted acid is 1:3, forming a volcano-shaped concentration effect.
- The electron density of formaldehyde intermediates is influenced by Lewis acids, affecting the reaction rate.

## Abstract

Via inline-nuclear magnetic resonance measurements, the homogeneously catalyzed poly(oxymethylene dimethyl ether) fuel synthesis using trioxane and dimethoxy methane is investigated. Besides the Brønsted acid (BA) catalyst triflic acid (TfOH) different metal halides are studied as Lewis-acidic (LA) catalysts. Among the used LAs, MgCl2, the weakest based on electronegativity, reveals the highest catalytical activity. Additionally, the influence of the concentration of BA and LA is investigated. An increase in BA concentration leads to an exponential increase of the reaction rate, while increasing the concentration of the LA leads to a volcano plot with its optimum at a LA : BA ratio of 1 : 3. The influence of the LA on the electron density of the intermediate formaldehyde is concluded as the main factor for this behavior.

The cooperative effect of Lewis and Brønsted acids within the OME fuel synthesis was investigated via inline NMR monitoring.