Water diffusion in zeolite 4Abeds measured by broad-line magnetic resonance imaging

Single-Point Magnetic Resonance Imaging Study of Water Adsorption in Pellets of Zeolite 4A

“…The large error bars are a consequence of low signal intensity in the low water concentration region (c Ͻ 0.15 c ϱ ). Other studies (3,27) have reported two bulk T 2 components whose contributions depend on the hydration level. The single exponential behavior observed in the batch under investigation may be dictated by a dominant paramagnetic impurity effect.…”

“…1D SPRITE magnitude profiles were obtained with 0.55 mm nominal resolution and then normalized by the reference signal integral, corresponding to 0.16 g/cm 3 of water at 100% magnitude. For low hydration levels, data acquisition was performed every 1.5 h and the time between runs was gradually increased, reaching 12 h by the second week of measurements.…”

“…Zeolites, one type of microporous material, are used in separation processes and as catalysts and drying agents. In particular, zeolite 4A is an efficient absorbent for molecules with an effective size under 4 ϫ 10 Ϫ10 m. Its water capacity is 22-22 wt% (1), but oxygen and nitrogen are not adsorbed (3). As a result, zeolite 4A is widely used as a drying agent for natural gas, liquid paraffins, and organic solvents.…”

Diffusion of Water at Low Saturation Levels into Sandstone Rock Plugs Measured by Broad Line Magnetic Resonance Profiling

“…An effective diffusion coefficient of the form D eff Å D 0 / D 1 exp(c/c 0 ) was first discussed by Barrer (15). More Noting, on the left-hand side, that c s ӷ c v , and on the rightrecently, it has been successfully used to fit water diffusion hand side that profiles in beds of zeolite 4A powder (16). In the latter case, its origin lies in a model in which water is transported in parallel either in the interparticle space in the vapor phase (16,17).…”

“…More Noting, on the left-hand side, that c s ӷ c v , and on the rightrecently, it has been successfully used to fit water diffusion hand side that profiles in beds of zeolite 4A powder (16). In the latter case, its origin lies in a model in which water is transported in parallel either in the interparticle space in the vapor phase (16,17). In the confined geometry of the pore space this is reduced by a tortuosity factor and by a porosity factor, which together are expected to be of order water by a factor of about 5, as might be expected for water has been kept constant throughout.…”