*2.5. Catalyst Stability and Reusability Study*

To perform the stability test of the prepared catalysts in this study, a freshly prepared 3% Zn/SiO2 catalyst was selected. The collected data from the HDO reaction at various times on stream (TOSs) were used for calculating the conversion efficiency of the phenol. The obtained results will reveal the variation in activity and selectivity of the catalyst applied with TOS. A reusability study was done in the fixed-bed reactor and the sample applied for the stability test was regenerated at 500 ◦C under the air atmosphere (for 1 h in an electrical furnace). The liquid products were collected and further analyzed using GC-FID analysis.
