Silicoaluminophosphate molecular sieves with AFI, AFO, AEL and CHA topologies have been investigated as a hydrocarbon trap by studying the temperature programmed desorption of toluene. The pore diameter is increased in the following order: SAPO-34 (d(p) = 0.38 nm) < SAPO-11 (0.39 nm x 0.63 nm) < SAPO-41 (0.43 nm x 0.70 nm) < SAPO-5 (0.73 nm). The capacity to adsorb hydrocarbon increases with increase of pore width. The effect of hydrothermal treatment over SAPO-5 shows that the stability is not affected significantly up to a temperature of 700 degrees C. Moreover, Si substitution is playing an important role in desorption temperature while capacity to adsorb toluene is mostly influenced by pore diameter. (c) 2004 Elsevier B.V. All rights reserved.