Single step synthesis of dimethyl ether (DME) from syngas on the bifunctional catalysts of CuO-ZnO-Al2O3 deposited on Al2O3-modified H-ferrierite was investigated to elucidate effects of Al2O3 modification of H-ferrierite in terms of CO conversion and DME yield. The enhanced catalytic activity was observed on the bifunctional catalysts at an optimum content of Al2O3 on H-ferrierite around 2.5-5 wt%. It is attributed to a higher dispersion of Al2O3 on H-ferrierite with an enhanced interaction of copper particles with Al2O3 modified H-ferrierite with a lower aggregation property by adjusting acidic sites and by increasing the dispersion of copper particles. The main role of Al2O3 on H-ferrierite is found to reduce strong acidic sites by depositing on the sites selectively, which resulted in showing a lower formation of byproducts. Both of copper surface area and amount of acidic sites are well correlated with an intrinsic activity (turn-over frequency; TOF), which revealed a structure-insensitive reaction character of a single-step synthesis of DME. The measurements of the dispersion of Al2O3 and copper particles with the number of acidic sites concomitantly were employed to verify the effects of Al2O3 modification of H-ferrierite though X-ray photoelectron spectroscopy, temperature-programmed methods and surface morphology characterizations.
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