Analysis of H2 Release from Organic Polycyclics over Pd Catalysts Using DFT

Abstract

Density functional theory (DFT) was used to study H2 release from dodecahydro-N-ethylcarbazole over Pd. Dehydrogenation of the molecule starts from the five-membered ring by weakening the axial C–H bonds adjacent to the N atom. In the adsorption mode identified for dodecahydro-N-ethylcarbazole, the five-membered ring was located on a hollow site and the axial H atoms adjacent to N were positioned atop Pd atoms with an adsorption energy of −95 kJ/mol. The two axial C–H bonds of the five-membered ring showed a large increase in bond distance upon adsorption, from 1.10 to 1.16 A, that was responsible for the weakening of these bonds. The adsorption mode for dodecahydro-N-ethylcarbazole explained the product distribution obtained from the dehydrogenation reaction with octahydro-N-ethylcarbazole and tetrahydro-N-ethylcarbazole identified as primary and secondary products, respectively. DFT was also used to investigate the structure sensitivity of dodecahydro-N-ethylcarbazole dehydrogenation observed on Pd cata...