Synthesis of polyoxymethylene dimethyl ether from methanol and formaldehyde over sulfonated PS@SiO2 core-shell nanospheres

Polyoxymethylene dimethyl ethers (PODEn) are oxygen-containing diesel fuel additives, which can efficiently reduce NOx and soot emissions. In this work, PolyStyrene with the size of 200-300 nm was prepared by soap-free emulsion polymerization. Sulfonated PS@SiO2 core-shell nanospheres with different organic group and silicon content were synthesized by stöber method, and evaluated for the synthesis of PODEn from methanol (MeOH) and formaldehyde (FA). With increasing the carbon chain length of organic group, the MeOH conversion and PODE3-6 selectivity catalyzed by sulfonated PS@SiO2 with organic group increased. It was found that the surface hydrophobicity of catalysts influenced the catalytic activity and could promote the formation of the long-chain PODEn. Moreover, the influence of catalyst doge, molar ratio of MeOH to FA and reaction temperature were investigated by using sulfonated PS@SiO2 as the catalyst. The result shows that 61.22% conversion of MeOH and 21.61% selectivity for PODE3-6 have been achieved under the optimal conditions.