Methanol dehydration to dimethyl ether over KFI zeolites. Effect of template concentration and crystallization time on catalyst properties and activity

The transition to renewable energy from fossil fuels in the transportation industry is crucial for the environment. Dimethyl ether (DME) is a promising substitute for fossil fuels as it can be produced from green hydrogen and CO2 from direct air capture, and in addition has reduced CO, SOx, and NOx emissions upon combustion. This study investigated KFI-type zeolites as catalysts for methanol dehydration to DME while comparing ZSM-5 and γ-Al2O3 as benchmarks. The influence of template (18-Crown-6) concentration and hydrothermal crystallization time were examined on catalyst properties using characterization techniques including XRD, SEM, BET, DRIFTS, NH3-TPD, and TGA. Activity and stability tests revealed that an optimum KFI zeolite, synthesized with a molar Si/Template ratio of 10:1 and 7 days of crystallization, has superior performance compared to traditional catalysts. The catalyst achieved thermodynamic equilibrium conversion at approximately 185 ℃ (91%) due to high acidity (2466 μmol g–1) and maintained activity for > 100 h. The stable and superior activity is attributed to mesoporous structure and numerous weak acid sites.