Phosphate-modified TiO 2 -SiO 2 mixed oxide catalysts have been prepared by varying the method of preparation, source and concentration of phosphate ion. The prepared catalysts were compared for their catalytic activity/selectivity in nitration of toluene. The characterisation of the catalysts was performed using X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermal analysis (TG-DTA), nitrogen adsorption-desorption methods, surface acid strength measured by Hammett indicator method, surface acid sites measured by amine titration method, and phosphate content measured by UV-VIS spectrophotometry. The XRD patterns revealed that phosphate ion stabilises the anatase phase up to 1173K activation. FT-IR results show that phosphate species strongly bound bidentately, and that both the internal weakly H-bonded hydroxyl groups and free hydroxyl groups are present on TiO 2 -SiO 2 mixed oxide support. Surface area and surface acidity are found to increase with the increase in phosphate loading up to 7.5wt.% and thereafter the values decrease drastically. However, average pore radius and total pore volume shows the reverse order. Phosphated samples prepared using H 3 PO 4 as the source of phosphate ion exhibit higher acidity, and surface area but lower porosity than the samples prepared from (NH 4 ) 3 PO 4 , though both the samples contain the same amount of phosphate (7.5wt.%). Similar results were also observed when varying the method of preparation. TiO 2 -SiO 2 samples prepared at pH=3 exhibit higher acidity and surface area but lower porosity than the samples prepared at pH=7. The acid strength of 7.5P/TiO 2 -SiO 2 (H) is found to be stronger than that of 100% concentrated H 2 SO 4 . The material modified with phosphate ion was found to be an efficient and selective catalyst for solvent-free mono-nitration of toluene. Selectivity to the para-product is correlated with the porosity of the material.