Synthesis and kinetic modeling of functionalized oxymethylene ethers (f-OMEs) based on lactic acid derivatives and formaldehyde

Due to modern civilization's dependence on finite fossil resources, there is a growing need to implement a circular economy. Catalyzed acetalization reactions could contribute to achieve this goal. In such reactions, a wide variety of aldehydes and alcohols can be converted into acetals, which are known for their good recyclability and non-toxicity. Hence, this work focused on the utilization of acetalization reactions to produce novel and facile degradable building blocks for the chemical industry. The educts employed were the lactic acid derivatives ethyl lactate and butyl lactate, as well as formaldehyde, an important C1 bulk chemical that can potentially be produced from green methanol. The synthesis of functionalized oxymethylene ethers (f-OMEs) using the lactic acid derivatives and formaldehyde was performed for the first time. Based on an initial catalyst screening, the cheap and eco-friendly clay material montmorillonite K10 was employed as the catalyst with the highest selectivity for the desired acetals. The different reactivities of the tested solid acid catalysts are discussed. The conversion values reached up to 60%, and the selectivity for f-OMEs reached up to 70%, depending on the reaction conditions. Catalyst screening and experiments covering the relevant reaction conditions were initially carried out in a batch reactor. Subsequently, the process was successfully implemented in a continuously operating fixed-bed reactor, demonstrating the first steps for scale-up and further selectivity control. After a systematic study of the varying reaction conditions, a reaction network was proposed, and a kinetic model to estimate product distributions was developed. The validation of the model showed that the conversion prediction was mostly within a relative deviation of ±30%. The model exhibited good applicability to batch and fixed-bed reactors, making it a useful tool for process upscaling. A solvent-free and scalable production process for f-OMEs was developed, and the novel substances were characterized.