Ultrasound Assisted Preparation of CuO-ZnO-Al2O3/HZSM-5 Nanocatalyst for Direct Conversion of Syngas to DME

A series of CuO-ZnO-Al2O3/HZSM-5 nanocatalysts prepared by impregnation, co-precipitation-physically mixing and combined co-precipitation-ultrasound methods and their catalytic activity have been investigated toward direct conversion of syngas to DME. The BET, XRD, FESEM and TPR-H2 techniques were used to characterize nanocatalysts. XRD results showed that HZSM-5 structure is not damaged even after it is loaded with CuO-ZnO-Al2O3 nanoparticles. FESEM analysis showed that, ultrasound energy has been enhanced the dispersion of CuO-ZnO-Al2O3 on HZSM-5 resulting uniform coating of HZSM-5 surface by active phase. Size distribution histogram of CZA/HZSM-5 nanocatalyst synthesized via co-precipitation-ultrasound method showed the active phase particle size is between 25.7-125.4 nm with an average size of 47.86 nm. TPR-H2 profiles indicated that reducibility of co-precipitation-ultrasound nanocatalyst is higher than other catalysts. The effect of synthesis method on the catalytic performance was investigated at 200-300°C, 10-40 bar, GHSV=600 cm3.g/h and H2/CO=2. It is found that employing of ultrasound energy have great influence on the dispersion of CO hydrogenation function and consequently the DME synthesis performance. The physically mixing of CuO-ZnO-Al2O3and HZSM-5 resulted in the low activity, indicating that the closest packing of both active sites for CO hydrogenation and methanol dehydration is required for direct synthesis of DME. The durability of ultrasound assisted synthesized nanocatalyst was investigated during syngas to DME reaction. The nanocatalyst loses negligible activity over the course of reaction due to coke formation on copper species.

کلیدواژه ها:

ZnO-CuO-Al2O3 ، HZSM-5 ، Co-precipitation ، Ultrasound ، Syngas ، DME