LAUSR

Abstract A series of molecular sieve-immobilized Bronsted acidic ionic liquids (BAILs@MS) was prepared, characterized and utilized as efficient catalysts for the synthesis of polyoxymethylene dimethyl ethers (PODE n or DMM n ) from methylal (DMM 1 ) and trioxane (TOX). Combined characterization results from fourier transform infrared (FT-IR) spectroscopy, elemental analysis, thermogravimetry (TG), N 2 adsorption-desorption (Brunauer-Emmett-Teller, BET) isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature-programmed desorption of ammonia (NH 3 -TPD), suggested that the synthesized BAILs were successfully immobilized on the surface of molecular sieves through covalent bonds. Moreover, the catalytic performance tests demonstrated that NaZSM-5 immobilized SO 3 H-functionalized ionic liquids (ILs) i.e., BAILs@NaZSM-5, exhibited excellent activity for the acetalation of DMM 1 with TOX, compared to the homogeneous catalysis of the precursors ([MIMBs]HSO 4 ) as well as other molecular sieve-supported ILs. The influence of catalyst concentration, molar ratio of DMM 1 to HCHO, temperature and reaction duration on the catalytic activity were investigated by employing [NaZSM-5IMBs]HSO 4 as the catalyst. It was demonstrated that a superior conversion of formaldehyde (FA) (90.3%) and excellent selectivity for DMM 3-8 (53.5%) has been achieved in mild conditions (110 °C, 2.5 MPa for 2 h). Additionally, the catalyst can be effortlessly separated by filtration and reused more than ten times without significant loss of activity.