Recent progress in the application in compression ignition engines and the synthesis technologies of polyoxymethylene dimethyl ethers

Abstract Polyoxymethylene dimethyl ethers (PODE) have higher cetane number and oxygen content than mostly used oxygenated fuels. Thus, PODE are believed to be a promising fuel substitute for compression ignition engines and have been intensively studied in compression ignition engines. In recent 5 years, due to the technical breakthrough for industrialized production of PODE in China, PODE property measurement, synthesis technology and application in compression ignition engines have been investigated extensively. This article summarizes the findings concerning PODE synthesis mainly in China and PODE application in compression ignition engines around the world. The measuring results of properties of PODE with different polymerization degrees and effects of PODE on the properties of PODE/diesel blends are integrated. Then, the present synthesis technologies which have realized industrialized production and the potential synthesis technologies in future are discussed. Furthermore, the results of application of PODE in the conventional diesel combustion mode and new compression modes are discussed. Finally, the preliminary findings of PODE oxidation mechanism are demonstrated. In all the polymers of PODE, PODE 4–5 exhibit better properties for engine application based on measuring data. Blending PODE into diesel increases fuel cetane number moderately. PODE have been proved to improve combustion and emission characteristics both in conventional and new compression ignition modes in most of the experimental investigations. The absence of C C bond in the molecule structure, avoiding the pathways of the formation of alkenes, provides more potential in reducing soot emissions. Although significant achievements have been achieved in the synthesis of PODE, realization of PODE synthesis from methanol/formaldehyde still need to be investigated.