Abstract:
Benzene (B), toluene (T), and xylenes (X) are important raw materials for petrochemical industry. These aromatics are normally produced by the catalytic reforming, pyrolysis gasoline, and coal that require petroleum as the raw material. Nowadays, the catalytic transformation of renewable sources, such as bio-ethanol, is an interesting process for alternatively producing aromatic hydrocarbons. From previous work. 2.0 wt % Ga₂O₃/HZSM-5 relatively produced higher amount of toluene and m-xylene than that of other aromatics. The transformation of these two aromatics to more valuable petrochemicals is a challenge. Consequently, for this research work, the investigation on the catalytic transformation of bio-ethanol to liquid hydrocarbons was divided into two parts; (1) the two consecutive layers of catalysts, and (2) the HZSM-5 catalysts modified with an acidic oxides of group VA elements. For the first part, 2.0 wt % Ga₂O₃/HZSM-5 was packed as the first layer in the reactor, and a catalytic layer of one of these zeolites; H-X, H-Y, or H-Beta was consecutively packed as the second layer, aiming to further convert m-xylene and toluene, produced from the first layer, to more valuable aromatics. It was found that the highest acid density of H-X and the highest acid strength of H-Beta promoted the conversion of light hydrocarbons to C9 and especially C10+ aromatics. For the second part, a series of P₂O₅, Sb₂O₅, and Bi₂O₅ loaded on HZSM-5 expectedly being able to increase acid strength of the support were also studied on the enhancement of aromatics production. It was found that the moderate acid strength of P₂O₅/HZSM-5 favored the formation of p-xylene, and gave the highest ratio of p-xylene/xylenes, whereas the highest acid strength of Bi₂O₅/HZSM-5 gave the most selective to C10+ aromatics. In addition, the fraction of gasoline range was the main composition in the liquid products, followed by kerosene.
