Adsorption and Desorption of a Model Hydrocarbon Mixture Over HY Zeolite Under Dry and Wet Conditions

Adsorption behavior of a hydrocarbon mixture (propene, toluene, decane) mimicking Diesel cold-start was investigated under dry and wet conditions for commercial HY zeolites with a Si/Al ratio ranging from 2.5 to 100. Textural and structural characterizations were carried out using N2 adsorption at 77 K and X-ray diffraction. In situ FTIR spectroscopy of adsorbed pyridine was exploited to probe acidic sites. The methodology used in this study consisted of adsorption phase at 35 °C with several kinds of mixtures followed by a Temperature-Programmed Desorption (TPD) at 10 °C/min. At high Si/Al ratio, a competitive thermodynamic adsorption between toluene and decane was demonstrated. To the opposite, propene is substantially not adsorbed whatever the Si/Al ratio of the zeolite. By decreasing the Si/Al ratio, the presence of large amounts of acidic sites enhances adsorption of unsaturated hydrocarbons. Water adsorption was found to be detrimental for HC storage due to hydrophilic nature.