Large-scale production of oxymethylene dimethyl ethers

Oxymethylene dimethyl ethers (OME) show promising solubility and combustion properties for applications in various chemical processes and sectors. They enable clean and quasi soot-free combustion, which can strongly reduce NOx emissions. Besides reducing local emissions, OME can strongly reduce CO2 emissions by replacing fossil diesel fuel if their production is based on sustainable methanol. Various process concepts for their production were proposed and investigated, but most of them prevail signifcant bottlenecks, which prevent their demonstration and scale-up in the near future. One of the main hurdles is the separation of the by-product H2O which forms in various process steps from H2 and CO2 via methanol towards OME3-5. Especially in the OME3-5 sub-process the separation of H2O is challenging considering a large scale production plant. Therefore, the novel COMET (clean OME technology) process concept is introduced and experimentally demonstrated by relying only on state-of-the-art process units. The COMET process relies solely on methanol and formalin as feedstock and overcomes the challenging water management using a reactive distillation column. As the heart of the production process, a suitable catalyst is required to selectively form the target OME product mixture. Various catalysts have been investigated for OME synthesis focusing on selectivity and activity. The investigations in this work focus on commercial heterogeneous catalysts and compare not only the conversions, selectivities and the target product yield but also the activity, side product formation and thermal stability of the synthesis products. Various ion exchange resins, zeolites and Nafon catalysts were applied for the OME synthesis in a batch autoclave at 60 ◦C for the aqueous reaction systems methanol-paraformaldehyde and the anhydrous reaction system OME1-trioxane. Investigations of the synthesis products in a micro distillation setup showed that all applied catalysts lead to active species in the synthesis product, negatively impacting its thermal stability. This indicates that a synthesis product handling step is necessary prior to the downstream purifcation. Based on these investigations, ion exchange resins are identifed as the most suitable for industrial OME synthesis due to their higher activity and lower side product formation. The COMET process and four additional processes for the production of OME3-5 are simulated and evaluated, and key performance indicators are defned and compared with alternative processes from the literature at a scale of 100 kt a-1 OME3-5 product for the system boundary starting from H2O electrolysis and CO2 capture. The overall energy efciency for all considered OME3-5 production processes is < 40 % even after heat integration. However, the overall energy efciency can be signifcantly improved if high temperature heat pumps (HTHP) are used to lift the temperature level of low temperature excess heat streams. The evaluation shows that by upgrading excess heat streams using HTHP, a process overall energy efciency of higher than 61 % can be achieved compared to 30 % in a conventional integrated processes. Thereby, the excess heat stream from H2O electrolysis already covers the low temperature heat demand for CO2 capture via direct air capture, not only for OME but also for various PtX products. The experimental validation, simulation work and evaluation methodologies in this work pave the way towards further basic and detailed engineering of industrial scale OME production processes.

Author dc:creator

• Mantei, Franz Kaspar

Advisor dc:contributor.advisor

• Kraume, Matthias

Licence dc:rights.uri

• https://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Identifier URI

https://doi.org/10.14279/depositonce-19272

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/20474