In the present work a detailed study of the effect of pH, in the range of 0-4.5, over the mesostructure of SBA-15 and catalytic transformation of 1-butene has been carried out. Also, the effect of silica source hydrolysis on the Al incorporation at different pH was studied varying the order of addition of an aluminium salt, before and after hydrolysis. The samples were characterized by SEM, TEM, ICP and N-2 adsorption. The materials showed a highly ordered hexagonal mesostructure for all the pH range studied. A decrease in particle size with increase of pH was observed. Al incorporation was favoured as pH increased; the highest incorporation was obtained at pH 4.5. An important effect of hydrolysis on Al incorporation was observed depending of metal incorporation. Hydrolysis had also an effect on the distribution and strength of the acid sites. The materials with the highest skeletal isomerization selectivity were those synthesized at pH 4.5. (C) 2010 Elsevier B.V. All rights reserved.