Preparation and catalytic performance of CuO-znO-AlO3/clinoptilolite nanocatalyst for single-step synthesis of dimethyl ether from syngas as a green fuel.

Direct conversion of syngas to dimethyl ether was successfully carried out over a clinoptilolite supported nanocatalyst modified by NH4Cl. A series of bifunctional nanocatalysts, CuO-ZnO-Al2O3 (CZA) over Clinoptilolite with different loading of CZA, were prepared via coprecipitation method and their catalytic performance were compared in a fixed-bed high pressure reactor. The catalysts were characterized by XRD, BET, FESEM, FTIR and TPD-NH3 techniques. The physicochemical analysis showed that with NH4CI treatment, the specific surface area of clinoptilolite increased obviously, while its crystallinity decreased slightly. It was found that the crystallinity of clinoptilolite was dramatically changed, whereas crystallinity of CuO has not been influenced significantly by the increase of CZA content. Moreover, with increasing the CZA/Clinoptilolite ratio, the specific surface area of nanocatalysts decreased. It is shown that the CZA particle size is distributed between 30.5-131.2 nm with an average size of 70.6 nm in which 77.8% of the particles are in the range of below 100 nm. The TPD-NH3 patterns showed that the number of the acid sites of the nanocatalysts decreased with the increase the CZA content. The influence of reaction pressure was investigated, confirming that the optimal reaction pressure for this catalyst was 40 bar. The catalytic performance is shown that the CZA/Clinoptilolite = 2 nanocatalyst had higher activity, selectivity due to its higher acidic sites.