Textural damage of cation-exchanged LTA zeolites studied by gas adsorption

Amari, Djilali; Ginoux, J. L.; Bonnetain, L.

doi:10.1016/0144-2449(94)90054-x

Cited by 10 publications

(6 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Remy and Poncelet (1995) suggested that the DR equation overestimated W 0,DR , with respect to W 0,t , when a solid presents an important external surface. Our value of S ext for NaX, 2.3 m 2 g −1 , is close to that found by Ginoux (1983), namely 2 m 2 g −1 and by Amari et al (1994) for NaA, i.e. 3.7 m 2 g −1 .…”

Section: Nitrogen Adsorptionsupporting

confidence: 78%

See 1 more Smart Citation

Adsorptive properties of X zeolites modified by transition metal cation exchange

et al. 2011

View full text Add to dashboard Cite

The ionic exchange of the NaX zeolite by Ni 2+ and Cr 3+ cations was progressively driven and studied by adsorption of nitrogen and carbon dioxide. For each cationexchanged X zeolite sample, the development of characteristics such as profile of isotherms, RI criterion, isosteric adsorption heat and microporous volume using both the Dubinin-Radushkevich (DR) equation and the t-plot, was followed through the nitrogen adsorption. Results show that the cationic exchange process, in the case of Cr 3+ introduced at middle degree, is accompanied by a textural damage for Cr(x)X, in contrast to Ni 2+ -exchanged X zeolites. This degradation occurs without significant presence of mesopores, because the RI criterion values were found to be much lower than 2.2. The CO 2 adsorption isotherms were measured at intervals of 30 K from 273 K and the equilibrium pressures ranged from 0.5 to 600 Torr. The experimental data were correlated by the Toth model. The associated three adjustable parameters were estimated by nonlinear least-squares analysis. The effect of temperature on

show abstract

Section: Nitrogen Adsorptionsupporting

confidence: 78%

“…RI is somewhat higher for Cr(45)X, namely 1.67. Amari et al (1994) reported that RI changes either when the external surface or the microporous volume varies. Bearing in mind that cations act as adsorption centres, their distribution among non-framework sites determines their adsorptive behaviour.…”

Section: Nitrogen Adsorptionmentioning

confidence: 98%

Adsorptive properties of X zeolites modified by transition metal cation exchange

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Similarly, after cation exchange, the fact that only the first introduction of CO2 result in a relatively high heat of adsorption (80-90 kJ. Mol -1 ) does not assume that there is another type of site where takes place chemisorptions.This is not comparable with those obtained for the 4A zeolite which is about 120 kJ.mol -1 , and which calorimetry and IR spectroscopy studies indicate the chemisorptions onto zeolite 4A (Ginoux and Bonnetain, 1991;Amari et al, 1994;Delaval et al,1986;Takaishi et al, 1975) leading to two possible forms: carboxylate or carbonate; it explains the high heats observed for less than 0.3molec.cav -1 . The principal CO2 adsorption sites in the ZK-4 zeolite are of type Na (I), responsible of a strong heat of physical absorption and absence of the CO2 chemisorptions in ZK-4 could be explained starting from the assumption that CO2 is chemically absorbed on a cationic pair, in fact the missing Na (II) -Na (III) pair in ZK-4 (Ginoux, 1983).…”

Section: +contrasting

confidence: 56%

Thermodynamic Study of Light Organic Molecules Adsorption onto ZK-4 Zeolite

Chalal

Hamaizi

Viciana

et al. 2014

JAC

View full text Add to dashboard Cite

In this work, we were interested to the interactions of various light gases (critical temperature not exceeding 31 °C) with the zeolite ZK-4 and its varieties exchanged at temperatures close to ambient. The interest first practice since these gases are frequently encountered in industry, and most separations, that concern them by pressure swing adsorption (PSA) are carried at room temperature. By working in these conditions, we will be in the scope of application of Henry's law, which will allow us to better characterize the adsorption of the first molecules (gas-solid interaction). The thermodynamic study should enable us to identify the type of adsorption (localized, non-localized) by applying a theoretical model explaining the experimental results. The choice of the adsorbate was guided by the behavior of the introduced molecules toward the compensating cations present in the zeolite framework. These probe molecules having a specific interaction with zeolitic cations: N2, CO2 (highly quadripolar), C2H4 (double bound) or C3H8 which do not exhibit neither. Final results show that adsorption of nitrogen on ZK-4 sodic form is made in a located way on five sites following Langmuir model and none of CO2 and C2H4 chemisorptions was revealed. Besides, the gaseous molecules interactions in presence of divalent cations replacing sodium in ZK-4 are much less higher than in the case of zeolite 4A, and are characteristic of physisorption on relatively heterogeneous sites.

show abstract

“…Broadening of the XRD diffraction bands of LTA was observed with increasing Ni loadings (see Figure S1 in the Supporting Information), indicating a certain loss of crystallinity due to the ion exchange. 35,36 While a hysteresis for the N 2 sorption was not observed for Ca-LTA (Figure S2), the sorption volume of the Ni-containing catalysts showed important differences during adsorption and desorption, pointing to an increase in the mesopore volume and a decrease in the micropore volume (Table S1). To minimize the effect of local lattice destruction, the loading of Ni was limited to 6 wt % on Ni-Ca-LTA.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Dimerization of Linear Butenes on Zeolite-Supported Ni²⁺

et al. 2018

View full text Add to dashboard Cite

Nickel- and alkali-earth-modified LTA based zeolites catalyze the dimerization of 1-butene in the absence of Brønsted acid sites. The catalyst reaches over 95% selectivity to n-octenes and methylheptenes. The ratio of these two dimers is markedly influenced by the parallel isomerization of 1-butene to 2-butene, shifting the methylheptene/octene ratio from 0.7 to 1.4 as the conversion increases to 35%. At this conversion, the thermodynamic equilibrium of 90% cis- and trans-2-butenes is reached. Conversion of 2-butene results in methylheptene and dimethylhexene with rates that are 1 order of magnitude lower than those with 1-butene. The catalyst is deactivated rapidly by strongly adsorbed products in the presence of 2-butene. The presence of π-allyl-bound butene and Ni-alkyl intermediates was observed by IR spectroscopy, suggesting both to be reaction intermediates in isomerization and dimerization. Product distribution and apparent activation barriers suggest 1-butene dimerization to occur via a 1′-adsorption of the first butene molecule and a subsequent 1′- or 2′-insertion of the second butene to form octene and methylheptene, respectively. The reaction order of 2 for 1-butene and its high surface coverage suggest that the rate-determining step involves two weakly adsorbed butene molecules in addition to the more strongly held butene.

show abstract

Textural damage of cation-exchanged LTA zeolites studied by gas adsorption

Cited by 10 publications

References 30 publications

Adsorptive properties of X zeolites modified by transition metal cation exchange

Adsorptive properties of X zeolites modified by transition metal cation exchange

Thermodynamic Study of Light Organic Molecules Adsorption onto ZK-4 Zeolite

Dimerization of Linear Butenes on Zeolite-Supported Ni²⁺

Contact Info

Product

Resources

About

Textural damage of cation-exchanged LTA zeolites studied by gas adsorption

Cited by 10 publications

References 30 publications

Adsorptive properties of X zeolites modified by transition metal cation exchange

Adsorptive properties of X zeolites modified by transition metal cation exchange

Thermodynamic Study of Light Organic Molecules Adsorption onto ZK-4 Zeolite

Dimerization of Linear Butenes on Zeolite-Supported Ni2+

Contact Info

Product

Resources

About

Dimerization of Linear Butenes on Zeolite-Supported Ni²⁺