DFT simulations and microkinetic modelling of 1-pentyne hydrogenation on Cu₂₀ model catalysts

Adsorption and dissociation of H₂ and hydrogenation of 1-pentyne on neutral and anionic Cu₂₀ clusters have been investigated using the density functional theory and microkinetic modelling. Molecular adsorption of H₂ is found to occur strictly at atop sites. The H₂ dimer is activated upon adsorption, and the dissociation occurs with moderate energy barriers. The dissociated H atoms reside preferentially on 3-fold face and 2-fold edge sites. Based on these results, the reaction paths leading to the partial and total hydrogenation of 1-pentyne have been studied step-by-step. The results suggest that copper clusters can display selective activity on the hydrogenation of alkyne and alkene molecules. The hydrogenated products are more stable than the corresponding initial reactants following an energetic staircase with the number of added H atoms. Stable semi-hydrogenated intermediates are formed before the partial (1-pentene) and total (pentane) hydrogenation stages of 1-pentyne. The microkinetic model analysis shows that C₅H₁₀ is the dominant product. Increasing the reactants (C₅H₈/H₂) ratio enhances the formation of products (C₅H₁₀ and C₅H₁₂).