In-situ regeneration mechanisms of hybrid catalysts in the one-step synthesis of dimethyl ether from syngas

One-step synthesis of dimethyl ether (DME) from H 2 /CO has been studied in a fixed bed reactor over hybrid catalyst CuOZnOAl 2 O 3 /γ-Al 2 O 3 -HZSM-5. The physicochemical properties of fresh and used catalysts were also studied by means of H 2 -TPR, XRD and N 2 O chemisorptions. The results showed that for deactivated catalysts by sintering, redox cycle was an effective method for in-situ regeneration. There were two different regeneration mechanisms according to various atmospheres: (i) For O 2 -syngas cycle, sintered Cu particles were re-dispersed and initial activity was restored mostly. The process was reversible, which was called reversible regeneration; (ii) for N 2 O (CO 2 )-syngas cycle, Cu particles could not be re-dispersed and catalytic activity was restored a little due to the regulation of surface state. On the other hand, this process could depress the deactivation velocity and was irreversible, which was called irreversible regeneration.