Selective hydrogenation of 1-Hexyne using PdNi/Al2O3 and NiMn/Al2O3

Abstract

Vinyl acetylene and 1-butyne are by-products in mixed C4 separation processes and They must be eliminated due to safety concern. However, C4 acetylene can be upgraded to higher value hydrocarbons such as 1,3-butadiene and 1-butene by using selective hydrogenation. For hydrogenation catalyst, Pd supported on alumina has been successfully utilized in hydrogenation process. Nevertheless, Pd is still relatively expensive, therefore other transitional metals e.g. Ni is suggested. In this study, 1-hexyne is selected to be a model acetylene compound. The scope of this work is to evaluate the activity and selectivity of 1-hexyne hydrogenation in mild conditions (40 ℃, 1.5 bar) using Pd/AI₂O₃ at different metal loading. Low loaded Ni on alumina exhibited the highest in 1-hexene selectivity improved in the order: 0.3%Ni> 0.3%pd> 1%Ni  1.5%Ni  2%Ni  3%Ni. Interestingly, Pd-Ni and Ni-Mn bimetallic catalysts at various Pd/Ni and Ni/Mn molar ratios exhibited superior 1-hexene selectivity. PdNi2.0/ AI₂O₃ and Ni/MnI.0/ AI₂O₃ bimetallic catalysts provide 1-hexene selectivity 87% and 92% at completed conversion. The catalysts were also characterized by BET, TPR. and H₂-chemisorption.