Initial Hydrogenations of Pyridine on MoP(001): A Density Functional Study

Abstract

The initial hydrogenations of pyridine on MoP(001) with various hydrogen species are studied using self-consistent periodic density functional theory (DFT). The possible surface hydrogen species are examined by studying interaction of H(2) and H(2)S with the surface, and the results suggest that the rational hydrogen source for pyridine hydrogenations should be surface hydrogen atoms, followed by adsorbed H(2)S and SH. On MoP(001), pyridine has two types of adsorption modes, i.e., side-on and end-on; and the most stable η(5)(N,C(α),C(β),C(β),C(α)) configuration of the side-on mode facilitates the hydrogenation of pyridine. The optimal hydrogenation path of pyridine with surface hydrogen atoms in the Langmuir-Hinshelwood mechanism is the formation of 3-monohydropyridine, followed by producing 3,5-dihydropyridine, in which the two-step hydrogenations take place on the C(β) atoms. When adsorbed H(2)S is considered as the source of hydrogen, slightly higher hydrogenation barriers are always involved, while the energy barriers for hydrogenations involving adsorbed SH are much lower. However, the hydrogenation of pyridine should be suppressed by the adsorption of H(2)S, and the promotion effect of adsorbed SH is limited.

Mechanistic Insights into Selective CO2 Conversion via RWGS on Transition Metal Phosphides: A DFT Study

“…To develop the MoP (0001) surface, the bulk parameters were first optimized. The obtained lattice parameters for the bulk MoP was found to be a = b = 3.246 Å, c = 3.21 Å, which is in good agreement with experimental ( a = b = 3.223 Å; c = 3.191 Å) and theoretical ( a = b = 3.252 Å; c = 3.216 Å) findings. The possible adsorption sites on MoP (0001), shown in Figure a, may be defined as hollow sites labeled as H M and H P , where H M is a 3-fold hollow site with Mo atoms only and H P is also a 3-fold hollow site with a P atom attached below.…”

DFT study of dihydrogen addition to molybdenum π-heteroaromatic complexes: a prerequisite step for the catalytic hydrodenitrogenation process

“…Thus, the reaction of full hydrogenation of 1N into 13 + 14 is exothermic (∆∆G = -9.7 kcal/mol). Similar mechanistic and thermodynamic results were previously observed for the hydrogenation of pyridine on a molybdenum(III) phosphide surface 27.…”

“…Similar mechanistic and thermodynamic results were previously observed for the hydrogenation of pyridine on a molybdenum(III) phosphide surface. 27 In the first stage one molecule of H 2 adds to complex 1N via a Kubas-type transition state TS1-N with an activation barrier DG = 30.4 kcal mol À1 . The dihydrogen character of TS1-N is evidenced by the Mo-H distances of 2.382 Å and 2.889 Å and .859 Å, respectively.…”

Adsorption and dissociation of H2S on Mo2C(001) surface-A first-principle study

“…For example, the hydrogenation of aromatic ring is required for the denitrogenation of heterocyclic nitrogencontaining compounds [6,30] and consequently, one of the possible source of hydrogen species is -SH group generated by the dissociation of hydrogen sulfide on the catalysts surface. [31] Molecular modeling and computational investigations have made important contributions towards understanding the structures and properties of molybdenum-based hydrotreating catalysts [32][33][34][35][36]. However, most of published studies of HDN on Mo 2 C surface focus on the reaction network [37] or the mechanism [33,38].…”