Facile sulfolane-modified resins for enhanced dimethoxymethane carbonylation†
Herein, a simple method was developed for the first time to pretreat sulfonic acid resin-based catalysts using different solvents (such as n-hexane, toluene, acetone, methanol, dimethyl sulfoxide, and sulfolane), and the as-treated resins were applied in DMM carbonylation. Except for sulfolane, the treatment solvents with a higher dipole moment resulted in a higher turnover number (TON) but lower DMM conversion and MMAc selectivity. SAresin-sulfolane-393 K exhibited excellent activity and stability for 50 h with an STY of 3.15 mmolMMAc (gcat h)−1 and nearly 100% MMAc selectivity. The Arrhenius plot of SAresin-sulfolane-393 K was generated from the reaction rate data at various temperatures, and the apparent activation energy was calculated to be 18.39 kJ mol−1. Karl Fischer analysis, in situ FT-IR analysis of CO adsorption, and static CO adsorption method indicated that the residual H2O in SAresin was significantly reduced and the CO adsorption capacity was obviously enhanced. The nitrogen adsorption–desorption isotherms, FT-IR spectra, and SEM and EDX-mapping images of SAresin-sulfolane-393 K proved that a larger average pore diameter and pore volume were generated, and sulfolane indeed entered the resin and changed the chemical composition of SAresin. The FT-IR spectra of the pyridine pre-adsorbed samples and Hammett acidity function (H0) confirmed that SAresin-sulfolane-393 K exhibited a stronger acid strength. The unusual activity and stability of SAresin-sulfolane-393 K are attributed to its stronger acid strength, low H2O content and excellent CO adsorption capability.