Kinetic and thermodynamic studies on [Omim]Cl/ZnCl2 catalyzed synthesis of polyoxymethylene dimethyl ethers.

Polyoxymethylene dimethyl ethers (OMEs) emerging as green additives for soot emission suppression receive significant attention due to their similar physical properties to diesel. Herein, the transformative pathways of dimethoxymethane (DMM) and trioxane reactions for OMEs production catalyzed by [Omim]Cl/ZnCl2 having different ZnCl2 content were demonstrated in combination with the clarification of active species, kinetic and thermodynamic properties, and chemical nature for trioxane decomposition and subsequential formaldehyde insertion steps. The role of [Omim]Cl, which could transform to [Omim]ZnCl3 or [Omim]Zn2Cl5 under different ZnCl2 content, laid in the formation of active zinc species and promotion of their homogeneity with reactants. The DMM chain growth, which followed the same mechanism and kinetic law, showed kinetic and thermodynamic regimes and had identical equilibrium distribution of OMEs. Only Zn2Cl5− species were active for trioxane decomposition, which was the kinetic‐relevant step, while both ZnCl3− and Zn2Cl5− were effective for DMM chain elongation. [ABSTRACT FROM AUTHOR]