Direct syngas to DME as a clean fuel: The beneficial use of ultrasound for the preparation of CuO-ZnO-Al2O3/HZSM-5 nanocatalyst

摘要

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 investigated toward direct conversion of syngas to DME. BET, XRD, FESEM, TPR-H2 and FTIR techniques were used to characterize nanocatalysts. XRD and FTIR results showed that structure of HZSM-5 is not damaged even after it is loaded with CuO-ZnO-Al2O3 nanoparticles. TPR-H2 profiles indicated that reducibility of co-precipitation-ultrasound nanocatalyst is higher than other catalysts. It is found that employing ultrasound energy has great influence on the dispersion of nanocatalyst and its catalytic performance. Size distribution histogram of this nanocatalyst indicated that active phase particle size is between 25.7 and 125.4 nm and their average size is 47.86 nm. The physically mixing of CuO-ZnO-Al2O3 and HZSM-5 resulted in the low catalytic activity, indicating that the closest packing of both active sites for CO hydrogenation and methanol dehydration is necessary for direct synthesis of DME. The nanocatalyst loses negligible activity over the course of reaction due to coke formation on copper species.