Selective hydrogenation of 1-hexyne using low loaded Pd, Pd-Cu and Pd-W supported on alumina catalysts

Vinyl acetylene and 1-butyne are by products from mixed C4 plants. Due to their ability to self-explode, these C4 acetylene compounds must be eliminated. Currently, these compounds are burnt away, however, it has been suggested that they could be upgraded to higher value hydrocarbons such as 1,3-butadiene and 1-butene. The selective hydrogenation of C4 acetylenes is proposed, but for convenient, this study selected 1-hexyne as a model C4 acetylene compound for liquid phase hydrogenation. The activity and selectivity of low loaded Pd, Pd-Cu/Al₂O₃ and Pd- W/Al₂O₃ catalysts were investigated. The atomic ratios of Pd/Cu and Pd/W were varied at 0.25, 0.5, 1.0, 1.5 and 2.0, and were utilized in the liquid phase hydrogenation of 1-hexyne under 1.5 bar of H₂ and 40 ºC. It was found that the catalytic performance of Pd-W/Al₂O₃ was better than that of Pd/Al₂O₃ and of Pd-Cu/Al₂O₃ at the same ratio. Moreover, Pd-W/Al₂O₃ catalyst (at Pd to W ratio of 1) exhibited the optimum activity and selectivity for selective 1-hexyne hydrogenation.