A series of AIMCM-41 molecular sieves was synthesized starting from a hydrogel with the following molar composition: ICTMABr: 4.58SiO(2):(0.437 + X)Na2O:XAl2O3:200H(2)O. Tetramethylammonium silicate (TMAS) was used as silicon source and cethyltrimethylammonium bromide (CTMABr) was used as structure template. The obtained materials were characterized by nitrogen adsorption, XRD, FT-IR and TG/DTG. Model-free kinetic algorithms were applied in order to determinate conversion, isoconversion and apparent activation energy to decomposition of CTMA+ species from the AIMCM-41 materials with different silicon/aluminium (Si/Al) ratios of 20, 40, 60 and 80. (c) 2006 Elsevier B.V. All rights reserved.