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 212h. 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.