Catalytic Ethanol Dehydration to Ethylene over Nanocrystalline χ- and γ-Al2O3 Catalysts

The study is aimed to investigate the combination of nanocrystalline gamma- and chi-alumina that displays the attractive chemical and physical properties for the catalytic dehydration of ethanol. The correlation between the acid density and ethanol conversion was observed. The high acid density apparently results in high catalytic activity, especially for the equally mixed gamma-and chi-phase alumina (G50050). In order to obtain a better understanding on how different catalysts would affect the ethylene yield, one of the most powerful techniques such as X-ray photoelectron spectroscopy (XPS) was performed. Hence, the different O is surface atoms can be identified and divided into three types including lattice oxygen (0, 530.7 eV), surface hydroxyl (OH, 532.1 eV) and lattice water (H2O, 532.9 eV). It was remarkably found that the large amount of O 1s surface atoms in lattice water can result in increased ethylene yield. In summary, the appearance of metastable chi-alumina structure exhibited better catalytic activity and ethylene yield than gamma-alumina. Thus, the introduction of metastable chi-alumina structure into gamma-alumina enhanced catalytic activity and ethylene yield. As the result, it was found that the G50050 catalyst exhibits the ethylene yield (80%) at the lowest reaction temperature ca. 250 degrees C among other catalysts.