Combination of Theoretical and Experimental Insights into the Oxygenated Fuel Poly(oxymethylene) Dibutyl Ether from n‑Butanol and Paraformaldehyde

Oxygenated fuel has the function of self-supplying oxygen during the combustion process, which can greatly improve emission performance and reduce diesel fuel soot production. In this paper, a novel oxygenated fuel poly­(oxymethylene) dibutyl ether (PODBE_n) is designed and synthesized through experiments in combination with density functional theory (DFT) calculation. The experimental results show that PODBE_n has the advantages of high cetane number (73.6), moderate density (868 kg/m³), and low condensation point (−72 °C). According to the DFT calculation results, the molecular (PODBE_n) polarity index of different polymerization degrees is similar to the value of diesel and has good mutual solubility with diesel. Moreover, the mechanism of the entire path of synthesis is calculated at the M06-2X/6-311G­(d,p) level of theory. The energetic profile reveals that the rate-determining step is the nucleophilic addition step with the highest barrier energy (TS1 = 21.59 kcal/mol). This work provides a feasible method to synthesize high-performance oxygenated fuel PODBE_n using NKC-9 ion-exchange resins.