Coking During DME Synthesis: A Calorimeter Study

Dimethyl ether (DME) is a promising alternative fuel for transportation and cooking. During the synthesis of DME, formation of coke is the primary cause for deactivation. With micro calorimeter experiments combined with mass spectrometry measurements we show here, that DME adsorbs on two different sites on H-ZSM-5 with heats of adsorption of about 120 and 95 kJ/mol. Exposure to DME at 230 degrees C for 3 h turns the samples brown due to coking and decreases the amount of adsorbed DME, but does not change the heat of adsorption. In contrast, no clear indication of coke formation was observed after the same treatment over gamma-Al2O3