241
and C–C coupling steps forming ethylene over Mo 4 C 2 cluster has been shown
in Fig. 6.
In addition, apart from Mo 4 C 2 cluster, another Mo 2 C 6 cluster (Fig. 7a) has also
been studied for all the C–H activation and C–C coupling reaction steps. A 119 kJ/
mol of first methane activation barrier (slightly higher than that on Mo 4 C 2 ) has been
calculated over the Mo
(1)
site of Mo 2 C 6 cluster. Reactant (a″), TS (CH 3 –H
TS
) and
product (b″) geometries showing C–H activation over Mo
(1)
-C Mo site have been
depicted in Fig. 7b. In results, it has been observed that of the two clusters, Mo 2 C 6
Fig. 5 Geometry of the reactant, TS and product states for (a) CH 3 –CH 3 coupling reaction and (b)
H 2 formation and desorption reaction steps over Mo 4 C 2 nanocluster (bond lengths in Å).
(Reproduced with permission from J. Phys. Chem. C 2018, 122, 11754–11764 [55]. Copyright
(2018) American Chemical Society)
Fig. 6 Potential energy diagram for C–H activation and C–C coupling reaction steps to form
ethylene over Mo 4 C 2 nanocluster. (Reproduced with permission from J. Phys. Chem. C 2018, 122,
11754–11764 [55]. Copyright (2018) American Chemical Society)
Thermocatalytic Conversion of Natural Gas to Petrochemical Feedstocks…