Silicoaluminophosphate molecular sieves as a hydrocarbon trap

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 (dp = 0.38 nm) < SAPO-11 (0.39 nm × 0.63 nm) < SAPO-41 (0.43 nm × 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 °C. Moreover, Si substitution is playing an important role in desorption temperature while capacity to adsorb toluene is mostly influenced by pore diameter.