The commercial catalysts and processes for light alkanes direct dehydrogenation (DH) have been disclosed. However, high cost of noble metal, environmental issue of multi-charged chromium ions, and the rapid deactivation caused by carbon formation are major drawbacks of the commercial DH catalysts. These deficiencies limit the development of commercial catalysts. Therefore, numerous researchers have tried to focus on efforts toward improving existing commercial catalysts or developing appropriate alternatives. Recently, unconventional binary mixed oxides have been applied to light alkanes dehydrogenation, such as CrZrOx, LaZrOx, bare alumina. The activity testing results have been confirmed that coordinatively unsaturated metal (i.g., Zrcus4+, Alcus) cations are DH active sites. Herein, we prepared two kinds of unconventional binary ZnO/ZrO2 heterogeneous catalysts for isobutane DH by a hard-template method, namely ZnZrO-x, and by mechanically mixing, namely xZnO-ZrO2, respectively (i.e., x represents the Zn/Zr mole ratio). The properties of ZnZrO-x and ZnO-ZrO2 catalysts were characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy of pyridine (Py-IR) and N2-chemisorption as well as tested for catalysts activity and selectivity for direct isobutane DH. The highest DH activity was achieved over ZnZrO-x prepared though hard-template method with the isobutene selectivity of ca. 90% at isobutane conversion of 48.2% after 7 hours. The characterization and activity testing results indicated that Zrcus4+ species as Lewis acids over the reducted ZnZrO-x show isobutane DH activity. Furthermore, ZnO played a synergistic effect with ZrO2 in improving the isobutane DH performance. In addition, Methane and propene were main by-products due to catalytic creaking, which catalyzed by strong Lewis and Brønted acidic sites.

Unconventional binary ZnO/ZrO2 heterogeneous catalysts for direct dehydrogenation of isobutane to isobutene

255th National Meeting (2018)

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