High purity titanium dioxide (TiO2) nanoparticles were synthesised via a modified sol–gel method using titanium tetraisopropoxide (TTIP). XRD analysis showed that the synthesised product was TiO2 powder in anatase form. The sample possessed a relatively high surface area of 75.64 m2/g. The typical TEM images suggested that the crystalline phase product was composed of fine particles with dimensions between 17 and 20 nm. The synthesised material was used as a photocatalyst for the removal of mercaptans from gas–oil. The result showed that up to 78% of the mercaptans in gas–oil was removed using the synthesised TiO2 photocatalyst.