Novel polymeric acidic ionic liquids as green catalysts for the preparation of polyoxymethylene dimethyl ethers from the acetalation of methylal with trioxane.

A series of micro-mesoporous polymeric acidic ionic liquids (PAILs) have been successfully synthesized and subsequently characterized using Fourier transform-infrared spectroscopy, N2 adsorption-desorption isotherms, scanning electron microscopy and thermogravimetry. Furthermore, the catalytic performance of the synthesized PAILs was investigated for the acetalation of methylal (DMM1) with 1,3,5-trioxane (TOX), micro-mesoporous PAILs copolymerized by divinylbenzene with cations and anions exhibited moderate to excellent catalytic activities for the acetalation. In particular, VIMBs-AMPs-DVB, with higher specific surface area (25.51 m2 g-1) and total pore volume (0.15 cm3 g-1) displayed an elevated conversion of formaldehyde (82.2%) and selectivity for polyoxymethylene dimethyl ethers (CH3O(CH2O) n CH3; PODE n or DMM n ) n = 3-8 (52.6%) at 130 °C, 3.0 MPa for 8 h. Moreover, the influence of various reaction parameters was investigated by employing VIMBs-AMPs-DVB as the catalyst and it demonstrated high thermal stability and easy recovery.