The Arrhenius plots and Eyring plots for various catalysts at the DBT
HDS conversion lower than 30% are shown in Fig. 2. The active energies
Ea are calculated by the Calculation 10 based on the slopes of the
Arrhenius plots. The thermodynamic parameters including enthalpy changes
(△ H) and entropy changes (△ S) are calculated according to
the slopes and intercept of the linear Eyring plots respectively. The
above three parameters are concluded in the Table 6. It shows that the
values of Ea follow the sequence: NiMo/SBA-16 > NiMo/AT-10
> NiMo/AT-0 > NiMo/AT-5 >
NiMo/AT-2.5 > NiMo/AT-7.5. It is well recognized that the
higher active energy Ea is, the lower HDS efficiency is. The trend of Ea
values can be related with the HDS efficiencies over various catalysts
from Fig. 1. Meanwhile, the enthalpy changes (△ H) and entropy
changes (△ S) for various catalysts exhibit the same increasing
order of NiMo/AT-7.5 < NiMo/AT-2.5 < NiMo/AT-5
< NiMo/AT-0 < NiMo/AT-10 < NiMo/SBA-16. It
should also be noteworthy that the lower activation enthalpy value will
lead to a more rapid reaction rate for DBT HDS reaction. Therefore, the
kinetic and thermodynamic studies demonstrate that NiMo/AT-x catalysts
present better HDS performance than NiMo/SBA-16 due to the improvement
of acidity and dispersion and distribution of active phases.