Resumen

CAPCHA VARGAS, Dayana M. et al. Direct synthesis of dimethyl ether from syngas. Part I: preparation of bifunctional Cuo-ZnO/HZSM-5 catalysts by successive sinthesis and physical mixture. Rev. Bol. Quim [online]. 2019, vol.36, n.2, pp.91-103. ISSN 0250-5460.

Abstract The direct synthesis of dimethylether (DME) from synthesis gas (CO + H₂) requires bifunctional catalysts type CuO-ZnO/HZSM-5, where the CuO-ZnO performs the synthesis of methanol by its hydrogenation activity and the HZSM-5 zeolite performs the dehydration of methanol by its acid activity. In this work, two methods of preparation of the bifunctional catalyst are compared: by successive synthesis (catalyst name CuO-ZnO/S-HZSM-5) and by physical mixture (catalyst name CuO-ZnO/HZSM-5). For this purpose, CuO-ZnO, HZSM-5 and silicalite were first prepared and characterized. In the preparation of the bifunctional catalyst CuO-ZnO/S-HZSM-5, silicalite (S) was incorporated to favor the growth of crystals with MFI-like structure (Zeolite Socony Mobil - FIVE).. All catalysts were characterized by the technique of X-ray diffraction, reduction at programmed temperature and desorption of NH₃ at programmed temperature. The crystallinity of CuO in the CuO-ZnO, CuO-ZnO / S-HZSM-5 and CuO-ZnO-HZSM-5 catalysts was 67%, 49% and 64%, respectively. The maximum reduction temperature found for the CuO-ZnO / S-HZSM-5 was 306 °C, which differs from the bifunctional catalyst by physical mixing CuO-ZnO-HZSM-5 which was 282 °C, this change is related to the crystallinity of CuO, at a lower crystallinity of CuO; higher its reduction temperature. The CuO-ZnO / S-HZSM-5 catalyst has a Brönsted acidity equal to 0.37mol NH₃/kg comparable to the acidity of pure zeolite HZSM-5 (0.41mol NH₃/kg), while the CuO-ZnO- catalyst HZSM-5 has a lower Brönsted acidity, equal to 0.25mol NH₃/kg.

Palabras clave : Bifunctional catalyst; CuO-ZnO; HZSM-5; successive synthesis; physical mixture.

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