A method of preparing a modified catalyst support comprises contacting a catalyst support material with a modifying component precursor in an impregnating liquid medium. The impregnating liquid medium comprises a mixture of water and an organic liquid solvent for the modifying component precursor. The mixture contains less than 17% by volume water based on the total volume of the impregnating liquid medium. The modifying component precursor comprises a compound of a modifying component selected from the group consisting of Si, Zr, Co, Ti, Cu, Zn, Mn, Ba, Ni, Al, Fe, V, Hf, Th, Ce, Ta, W, La and mixtures of two or more thereof. A modifying component containing catalyst support material is thus obtained. Optionally, the modifying component containing catalyst support material is calcined at a temperature above 100° C. to obtain a modified catalyst support.