In-situ growth of supported embryonic TS-1 zeolite (<10nm)on a silica support was achieved by steam-assisted crystallization(SAC). The use of low amounts of TPABr and steam at a moderate temperatureof 130 degrees C was the key factor to control partial transformationof silica into supported embryonic TS-1. Compared with the referencecrystalline TS-1, supported embryonic TS-1 exhibits a higher activityin dibenzothiophene (DBT) oxidation (TOF: 8-275 h(-1) vs 2.7-160 h(-1) at 30-98 degrees C),a higher resistance to poisoning by nitrogen-containing compounds,and a higher selectivity (>97%) in the productive utilization oftheoxidant in DBT oxidation. The activity of the amorphous titanosilicate(TOF: 21.2-210 h(-1) at 30-80 degrees C),the solid precursor of the SAC process, was higher than that of theembryonic and the crystalline TS-1. The analysis of the structuralproperties-catalytic performance of these catalysts showedan improved accessibility to defective Ti active sites Ti(OH)(OSi)(3) with higher catalytic activity. The results of thisstudy should be encouraging to unearth many other active amorphouscatalysts with the potential of industrial application.