• Ferreira, Afp
• Rodrigues, Ae
• Ribeiro, Am
• Seabra, R.
• Gleichmann, K.

Abstract

In order to evaluate the adsorption properties for CO2, CH4 and N-2, from flue gas streams, or for natural gas sweetening, three binderless zeolite 4A adsorbents were studied. To characterize these materials, several techniques such as N-2 physisorption at 77 K, CO2 physisorption at 273 K, mercury intrusion, Scanning Electron Micrograph (SEM), Energy Dispersive X-ray and X-ray Diffraction (XRD) were employed. Adsorption equilibrium isotherms of pure gases (CO2, CH4 and N-2) were determined at 303, 343 and 373 K. The dual site Langmuir model was used to fit the experimental results for adsorption of CO2 and single site Langmuir model for the adsorption of CH4 and N-2. The CO2 was the adsorbate with the highest affinity for all zeolites 4A and N-2 the one with the lowest affinity. In terms of capacity by volume the binderless 4A with high density has its capacity significantly improved, since it has the same mass based capacity, but due to its higher density it has a higher volume based capacity. The isosteric heats of adsorption calculated by the Clausius-Clapeyron equation were in good agreement with literature values. The adsorption kinetics studies were performed at 308, 323 and 373 K with the Zero Length Column (ZLC) technique analysing the analytical solution of the mathematical model and the long time response. The results appear to indicate that the crystal diffusion is the controlling mechanism of the diffusion of CO2 for the high density binderless zeolites 4A.

Topics

• density
• impedance spectroscopy
• Carbon
• scanning electron microscopy
• x-ray diffraction
• Nitrogen
• Mercury