SAPO-11 molecular sieves have been synthesized in both the conventional synthesis system and the H2O-cetyltrimethylammomium bromide (CTAB)-butanol system by the hydrothermal synthesis method. Characterization of these samples by X-ray diffraction (XRD), infrared spectroscopy (IR) of the adsorbed pyridine, Si-29 solid-state magic-angle spinning (MAS), nuclear magnetic resonance (NMR), and catalytic test reaction reveals that SAPO-11 synthesized in H2O-CTAB-butanol system has small crystal sizes and larger amounts of Bronsted acid sites. Such sites not only give rise to an increase of n-dodecane conversion. isomer yield and selectivity, but also increase the monobranched isomer selectivity. (C) 2003 Elsevier B.V. All rights reserved.