*2.2. Catalyst Synthesis*

The incipient wetness impregnation method was used in this investigation to prepare the catalyst samples with various doping percentages of the zinc metal onto the silica surface. Silica-supported 3% zinc was prepared using 10 g of silica (catalyst support) and 0.31 g of the powdered Zn metal and some water. The compounds were mixed in a stirrer, roughly 2 h. Afterward, it was dried overnight in an electric oven at 105 ◦C. The dried sample was then taken to a furnace for the calcination step for 5 h under 500 ◦C and air atmosphere. Other impregnated samples were prepared with the same procedure.
