An Alternative Correlation Equation between Particle Size and Structure Stability of H−Y Zeolite under Hydrothermal Treatment Conditions

Abstract

The effect of particle size in the range of 0.16−2.01 μm on the hydrothermal stability of H−Y zeolite under hydrothermal treatment conditions similar to those used in FCC processes was investigated. The average particle size of 0.45 μm was found to be the optimum particle size of H−Y zeolite to retain a high percent crystallinity upon hydrothermal treatment. A new correlation was developed by plotting the relative crystallinity (C/C 0) against the reciprocal of the square root of the particle size (d 0) of Y zeolite. The correlation accurately predicts the hydrothermal stability of Y zeolite in small to medium particle sizes for a given temperature. For the larger particle sizes of Y zeolite (>0.45 μm), no exact correlation between particle size and hydrothermal stability was found, probably because of the presence of more structural defects in the zeolite, as shown by higher Brønsted/Lewis acid ratios.

Pure, single phase, high crystalline, chamfered-edge zeolite 4A synthesized from coal fly ash for use as a builder in detergents

“…The calibration standards were prepared using standard solutions which was certified by the supplier. Three calibration standards (20,40 and 60 mg/l) and a blank solution were used to calibrate the equipment. A linear calibration curve was obtained after calibration.…”

“…The particle size measurements were performed by laser beam scattering technique (Coulter LS230). From the particle size distribution (PSD) curves obtained, the sizes, of which 10, 50 and 90 vol.% of the particles in the samples were smaller, could be determined [37][38][39][40]. These particle sizes (by volume) were denoted by d(0.1), d(0.5) and d(0.9), respectively.…”

Catalytic conversion of N2O over palladium catalysts based on dealuminated faujasite

“…This result was confirmed by Triantafillidis et al [17], who suggested that treatments at relatively high temperatures, or in aqueous solutions with acidic species, lead to the agglomeration of the crystallites that result in the formation of significant macroporous structure. Furthermore, the decrease in the surface area can be explained by the collapse of the zeolite framework and the formation of amorphous silica and alumina, detected also by XRD, 29 Si-MAS-NMR and 27 Al-MAS-NMR, which causes the obstruction of the zeolitic pores. Diffusive reflectance infrared spectra of different samples are given in Figure 3 (A).…”

“…This observation indicates that a large number of extra-framework Si atoms are formed and the regular framework structure is lost. Furthermore, the 27 www.prkm.co.uk exhibited a strong peak at 60 ppm assigned to tetrahedrally coordinated Al species (Al IV ). The study by this technique indicates the creation of the extra-framework aluminium after the dealumination treatment, highlighted by the presence of aluminium atoms in an octahedral environment (δ ≈0 ppm) and pentacoordinated aluminium (δ ≈30 ppm).…”

“…The extra-framework aluminum species formed during dealumination may block a significant part of the strong Bronsted sites. On the other hand, the mesopores created contribute, in some cases, to improve the accessibility of acid sites [27]. Moreover, as the hydrothermal treatment at 625 °C preserves the structure of the zeolitic support, this could describe the acidic behaviour of this sample.…”