Effect of Ba impregnation on Al₂O₃ catalyst for 1-octene production by 1-octanol dehydration

This study investigated the effect of impregnating Ba into an Al₂O₃ catalyst on the acid-base property and catalytic activity in the dehydration of 1-octanol to produce 1-octene. The Ba/Al₂O₃ catalysts were prepared by the incipient wetness method with different Ba contents of 0.0–3.0 wt%, and characterized by ICP-MS, BET-BJH, XRD, pyridine-FTIR, and CO₂-TPD. The catalytic activity in 1-octanol dehydration was evaluated at 300, 350, and 400 °C with liquid hourly space velocity (LHSV) of 7–56 h⁻¹. As the amount of Ba increased, the density of the basic site on Ba/Al₂O₃ increased, and the strength distribution of the Lewis acid site (LAS) was changed. Under the reaction condition of 400 °C and LHSV = 7 h⁻¹, Ba/Al₂O₃ showed higher 1-octene selectivity and 1-octene purity compared with the pure Al₂O₃ even though the 1-octanol conversion was similar. This is because the added Ba eliminated the strong LAS, which, in turn, inhibited the side-reaction originating from the re-adsorption of 1-octene. When LHSV > 21 h⁻¹, Ba/Al₂O₃ catalysts showed decreased 1-octanol conversion but maintained high 1-octene selectivity and 1-octene purity. As the Ba content reached 2.0 wt%, 1-octene selectivity was decreased as the formation of dioctyl ether became more active than olefin production. Therefore, 1.5 wt% Ba/Al₂O₃ is the optimal catalyst for producing 1-octene from 1-octanol in terms of 1-octanol conversion, 1-octene selectivity, and 1-octene yield.