<p>This study examined the effects of two molybdenum impregnation methods, i.e., spray and wet impregnation, on the activity and selectivity of sulfated mesoporous silica (SO₄–SiO₂) in producing bio-jet fuel from used palm cooking oil through an atmospheric hydrotreatment process. For the wet impregnation method, 2% (w/w) molybdenum metal from (NH₄)₆Mo₇O₂₄·4H₂O was dissolved in 50 mL of deionized water, and 5&#xa0;g of SO₄–SiO₂ was soaked in this solution and stirred for 24&#xa0;h. In contrast, for the spray impregnation method, the same concentration of molybdenum was dissolved in 5 mL of deionized water and sprayed onto 5&#xa0;g of SO₄–SiO₂ using a spray bottle. Surprisingly, the spray impregnation method successfully produced the Mo/SO₄–SiO₂ catalyst, which exhibited higher acidity, BET surface area, and thermal stability than the wet impregnation catalyst. XPS data revealed that the spray catalyst was predominantly composed of Mo(IV) species, resulting in a liquid product conversion of 63.65%. The selectivity for bio-jet fuel (first drop–450&#xa0;°C) and the total bio-jet fuel yield were 84.71% and 51.29%, respectively. These results outperformed those obtained with the Mo/SO₄–SiO₂&#xa0;<i>wet</i> catalyst primarily composed of Mo(VI) species. Furthermore, the second and third applications of the Mo/SO₄–SiO₂&#xa0;<i>spray</i> catalyst produced promising total bio-jet fuel yields of 50.96% and 46.59%, respectively. Therefore, this catalyst, prepared using a straightforward method, shows significant potential as a candidate for the biofuel industry in the future to support a green aviation industry.</p> Graphical Abstract <p></p>