Effect of irradiation power and time on ultrasound assisted co-precipitation of nanostructured CuO–ZnO–Al2O3 over HZSM-5 used for direct conversion of syngas to DME as a green fuel

Nanostructured CuO–ZnO–Al2O3/HZSM-5 catalyst has been prepared by an ultrasound-assisted co-precipitation hybrid method. The effect of irradiation power and irradiation time have been studied by changing time (30, 45, 60 min) and power of the sonication (50, 100, 150 W) during the synthesis which led to different physiochemical properties of the nanocatalyst. The XRD, FESEM, EDX, FTIR and BET analyses exhibited smaller particles with higher surface area and less population of particle aggregates at longer and highly irradiated nanocatalysts. The nanocatalyst irradiated at 150 W for 60 min (the longest irradiation time and the most intense power) showed a very narrow particles size distribution. More than 65% of particles of this nanocatalyst were in the range of 1–30 nm. The performance of investigated nanocatalysts in direct synthesis of DME from syngas showed ultrasound-assisted synthesized nanocatalysts have higher CO conversion and DME selectivity in comparison to non-sonicated catalyst. Selectivity of DME in catalyst with 150 W and 60 min ultrasonic irradiation exceeds 80% while DME selectivity of non-sonicated catalyst barely reaches to 50%. Among sonicated nanocatalysts, with increasing power and time of irradiation, the nanocatalyst represents higher activity and DME selectivity. Time on stream test of sonicated nanocatalyst showed stability of the nanocatalyst in 1440 min at 40 bar and 275 °C.