TY - JOUR
T1 - Ab initio reaction path analysis of benzene hydrogenation to cyclohexane on Pt(111)
AU - Saeys, Mark
AU - Reyniers, M. F.
AU - Neurock, M.
AU - Marin, G. B.
PY - 2005/2/17
Y1 - 2005/2/17
N2 - First-principles density functional theory calculations were performed to obtain detailed insight into the mechanism of benzene hydrogenation over Pt(111). The results indicate that benzene hydrogenation follows a Horiuti-Polanyi scheme which involves the consecutive addition of hydrogen adatoms. A first-principles-based reaction path analysis indicates the presence of a dominant reaction path. Hydrogenation occurs preferentially in the meta position of a methylene group. Cyclohexadiene and cyclohexene are expected to be at best minor products, since they are not formed along the dominant reaction path. The only product that can desorb is cyclohexane. Along the dominant reaction path, two categories of activation energies are found: lower barriers at ∼75 kJ/mol for the first three hydrogenation steps, and higher barriers of ∼88 kJ/mol for steps four and six, where hydrogen can only add in the ortho position of two methylene groups. The highest barrier at 104 kJ/mol is calculated for the fifth hydrogenation step, which may potentially be the rate-determining step. The high barrier for this step is likely the result of a rather strong C-H⋯Pt interaction in the adsorbed reactant state (1,2,3,5-tetrahydrobenzene*) which increases the barrier by ∼15 kJ/mol. Benzene and hydrogen are thought to be the most-abundant reaction intermediates.
AB - First-principles density functional theory calculations were performed to obtain detailed insight into the mechanism of benzene hydrogenation over Pt(111). The results indicate that benzene hydrogenation follows a Horiuti-Polanyi scheme which involves the consecutive addition of hydrogen adatoms. A first-principles-based reaction path analysis indicates the presence of a dominant reaction path. Hydrogenation occurs preferentially in the meta position of a methylene group. Cyclohexadiene and cyclohexene are expected to be at best minor products, since they are not formed along the dominant reaction path. The only product that can desorb is cyclohexane. Along the dominant reaction path, two categories of activation energies are found: lower barriers at ∼75 kJ/mol for the first three hydrogenation steps, and higher barriers of ∼88 kJ/mol for steps four and six, where hydrogen can only add in the ortho position of two methylene groups. The highest barrier at 104 kJ/mol is calculated for the fifth hydrogenation step, which may potentially be the rate-determining step. The high barrier for this step is likely the result of a rather strong C-H⋯Pt interaction in the adsorbed reactant state (1,2,3,5-tetrahydrobenzene*) which increases the barrier by ∼15 kJ/mol. Benzene and hydrogen are thought to be the most-abundant reaction intermediates.
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U2 - 10.1021/jp049421j
DO - 10.1021/jp049421j
M3 - Article
C2 - 16851197
AN - SCOPUS:14544287251
SN - 1520-6106
VL - 109
SP - 2064
EP - 2073
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 6
ER -