Activity and deactivation studies for direct dimethyl ether synthesis using CuO–ZnO–Al2O3 with NH4ZSM-5, HZSM-5 or γ-Al2O3

Herein we investigate the use of CuO–ZnO–Al2O3 (CZA) with different solid acid catalysts (NH4ZSM-5, HZSM-5 or γ-Al2O3) for the production of dimethyl ether from syngas. It was found that of the solid acids, which are necessary for the dehydration function of the admixed system, the CZA/HZSM-5 bifunctional catalyst with a 0.25 acid fraction showed high stability over a continuous period of 212 h.As this particular system was observed to loose around 16.2% of its initial activity over this operating period this study further investigates the CZA/HZSM-5 bifunctional catalyst in terms of its deactivation mechanisms. TPO investigations showed that the catalyst deactivation was related to coke deposited on the metallic sites; interface between the metallic sites and the support near the metal-support; and on the support itself.

► Admixed CZA/acid catalysts tested for activity and deactivation.
► HZSM-5 catalyst has the most stable acid function during the storage.
► HZSM-5 possessed high activity at low temperature compared with other catalysts.
► High stability of the CZA/HZSM-5 catalyst with constant selectivity of DME.