| As emissions from gasoline engines become more regulated, attention has been focused on the start-up phase (cold-start), when emissions of hydrocarbons (HC) tend to be highest. In this thesis, a new strategy (i.e., single-file diffusion in 1-D zeolites) was proposed as a viable approach to control automotive HC emissions during cold-start period. The proposed method was successfully employed to trap lighter HC molecules, which are often desorbed before the catalyst reached its working (light-oft) temperature.;The MeAPO molecular sieves were found to be more hydrophilic than the Al-Si zeolites, and as such their HC adsorption capacities were significantly affected in the presence of water vapor in the exhaust gases. ZSM-12, SAPO-5 and FAPO-36 were all hydrothermally stable up to the examined temperature of 800°C, however with some reduction of their HC trapping capacities and temperature desorption maxima. ZSM-12 zeolite was selected as the most promising candidate for the automotive cold-start emission application, due to its superior HC trapping performance in the presence of inhibiting constituents (i.e., H2O, CO2 and H2O-CO2 mixture) and after hydrothermal ageing.;The adsorption properties of water and toluene in the 1-D samples were characterized using gravimetric adsorption isotherm method. The equilibrium adsorption data of both molecules were adequately described by the Langmiur-Freundlich model. The obtained model parameters (e.g., Henry's constant) were found to be dependent on the textural properties (e.g., BET area) of the samples. Furthermore, a macroscopic diffusion measurement technique (i.e., tracer Zero Length Column) was employed to provide, for the first time using such technique, an experimental evidence of the occurrence of anomalous, single-file diffusion in microporous adsorbents.;Temperature programmed desorption (TPD) of ethylene and toluene, as probe sorbates, was employed to screen a series of one-dimensional aluminosilicate (Al-Si) zeolites and metalloaluminophosphate (MeAPO) molecular sieves as potential HC traps. The performance of the synthesized samples as HC's traps was found to be affected by the type of framework substituted metal, extent of metal substitution, channel structure/diameter of the samples and presence of other constituents, such as water vapor and CO2. |
