Calculation of the hydrothermal long-term stability of zeolites in gas-desulphurization and gas-drying processes

Suckow, M.; Lutz, W.; Kornatowski, J.; Rozwadowski, M.; Wark, Michael

doi:10.1016/0950-4214(92)80039-l

Cited by 20 publications

(10 citation statements)

References 9 publications

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“…The rate of adsorption in those thermally and hydrothermally treated samples is the same as that in the fresh silicalite. These adsorption equilibrium data are used to estimate the parameters in the zeolite stability model proposed by Suckow et al (1992): Nomenclature b: Langmuir adsorption equilibrium constant defined by eq 1 (kPa-l) D,: micropore diffisivity in zeolite (cm2/s) DCo: preexponential rate constants defined by eq 5 (cm2/s) E: activation energy of micropore diffusion defined by eq EA: activation energy for the zeolite hydrolysis reaction k,: adsorption rate constant defined by eq 6 (s-l) kd: desorption rate constant defined by eq 6 (9-l) K O : preexponential rate constants for the zeolite hydrolysis where Z(t) is the normalized zeolite concentration which is characterized by the adsorption amount of ,302 on the zeolite in this work, 20 is the initial zeolite concentration (20 = 11, ko is the preexponential constant of the reaction constant for zeolite hydrolysis reaction, EA is the activation energy for zeolite hydrolysis reaction, w is the normalized water concentration in the zeolite, and a is an empirical equation constant. These equation parameters listed in Table 6 were estimated from the adsorption data presented in Table 6.…”

Section: Resultsmentioning

confidence: 99%

Sulfur Dioxide Sorption Properties and Thermal Stability of Hydrophobic Zeolites

Deng

Yue²

1995

Ind. Eng. Chem. Res.

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Adsorption isotherms of SO2 in air on hydrophobic dealuminated Y (DAY) zeolite and silicalite at SO2 partial pressures ranging from 0.5 to 5 kPa were measured by the gravimetric method. The SO2 sorption isotherms on these two zeolites at different temperatures (25-100 "C) can be correlated by the Langmuir equation a t low SO2 pressures (<2 kPa) and by the Freundlich equation in the whole SO2 pressure range studied. The sorption capacity of SO2 on silicalite is larger than that of the DAY zeolite. Selective surface adsorption rather than the pore-filling mechanism was observed on adsorption equilibrium in these two zeolites. The SO2 sorption and desorption kinetic data obtained on these two zeolites show the dominant role of the reaction of SO2 on the zeolite surface in the SO2 sorption or desorption process. The simple Langmuir adsorption kinetic model provides a good description of SO2 sorption and desorption kinetics on these two zeolites a t low SO2 partial pressures. The thermal stability of these two zeolites was studied by comparing the pore texture, crystalline structure, and SO2 adsorption ability of the fresh samples with those of the thermally treated samples at 550 or 850 "C under various caustic conditions. It was found that these two zeolites are thermally and chemically stable under the studied conditions.

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Section: Resultsmentioning

confidence: 99%

Sulfur Dioxide Sorption Properties and Thermal Stability of Hydrophobic Zeolites

Deng

Yue²

1995

Ind. Eng. Chem. Res.

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“…Moving to the scale of zeolite crystals, it is currently unfeasible to accurately model long timescale effects, such as diffusion and removal of EFAL from channels, aluminum readsorption, or the process of mesopore formation, although few attempts have been made at a coarse‐grained level. [ 141b,164 ] It has been hypothesized that these effects, rather than the barriers for individual bond breaking events, are the key reasons for selectivity of desilication over dealumination at high pH. [ 167 ] To investigate these processes, inexpensive simulation methods of high accuracy must be developed.…”

Section: Discussionmentioning

confidence: 99%

“…Suckow et al made a series of investigations of zeolite hydrothermal stability, according to acid and base hydrolysis mechanisms which were assumed to act simultaneously on AlOSi and SiOSi bonds in the pore and at the surface, via acidic and basic mechanisms, respectively. [156,164]…”

Section: Ph Effectsmentioning

confidence: 99%

Zeolite (In)Stability under Aqueous or Steaming Conditions

et al. 2020

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zeolites, modification of zeolite acidity for use as fluid catalytic cracking (FCC) catalysts or even for the preparation of novel zeolite frameworks. [1] Considering the significance of zeolite applications at the industrial level, a thorough understanding of zeolite (in)stability under aqueous conditions has been identified as a very important problem in catalysis and zeolite science. Zeolite (in)stability in water or under steaming conditions has been investigated by a number of experimental techniques, in particular magic angle spinning (MAS) NMR, IR, powder X-ray diffraction (PXRD), calorimetry and adsorption. Experimental studies have often been augmented by computational modeling and a large number of relevant theoretical papers can be found in the literature. While the main focus of this review is on reactive interactions of water with zeolites, it is also important to review the most important observations obtained for nonreactive water adsorption in zeolites. It is not surprising that all-silica zeolites, which exhibit negligible water uptake are stable even under conditions where Alcontaining zeolites lose crystallinity: the effective framework hydrolysis can only take place when sufficient water is present in the zeolite channel system. The amount of water inside the zeolite channels depends critically on the concentration of heteroatoms and/or framework defects, such as silanol nests, which show much higher affinity toward water than hydrophobic SiOSi bridges. Zeolite hydrophobicity increases with increasing Si/Al ratio and incomplete pore filling by water is commonly observed for zeolites with high Si/Al at standard pressure. It has been suggested already in the 1950s by Young that water can only adsorb on surface silanol groups, while the parts of the silica surfaces formed by SiOSi bridges are hydrophobic. [2] Both water adsorption in zeolites and zeolite (in)stability under aqueous conditions depend on the zeolite composition (Si/Al ratio, charge-compensating cations, and defect concentration in particular). Our primary goal is to review the most critical aspects of zeolite (in)stability for a broad range of temperature and partial water pressure (p 0), focusing on the framework zeolite composition (Si/Al ratio and presence of Ge, Sn, and Ti heteroatoms) and defect concentration. Zeolites (in)stability in water is discussed for increasing extent of framework degradation, starting from the nonreactive interaction with water, reversible hydrolysis of TO bonds, mild zeolite demetallation, mesopore formation, and total amorphization (Figure 1). Zeolites are among the most environmentally friendly materials produced industrially at the Megaton scale. They find numerous commercial applications, particularly in catalysis, adsorption, and separation. Under ambient conditions aluminosilicate zeolites are stable when exposed to water or water vapor. However, at extreme conditions as high temperature, high water vapor pressure or increased acidity/basicity, their crystalline framework can be destroyed....

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“…Mathematical models for the decomposition of zeolite frameworks under hydrothermal conditions were derived by Suckow et al (1992) and Ehrhard et al (1995). The first paper presents a model for dissolution of the Si O Si bonds of high-silica zeolites by an "alkaline" mechanism whereas the second one deals with the hydrolysis of the Al O Si bonds of high-alumina zeolites by "acid" mechanism.…”

Section: Modelingmentioning

confidence: 99%

Investigation and Modeling of the Hydrothermal Stability of Technically Relevant Zeolites

et al. 2005

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The dense-structured zeolites of types ZSM-5 (MFI) and mordenite (MOR) of different SiO 2 /Al 2 O 3 moduli are relatively stable under treatment by liquid water for 72 hours up to 513 K. The open-structured zeolites of types Y in dealuminated modification (FAU) and beta (BEA) undergo strong decomposition in the same range. For these two sample types a mathematical model for the decomposition of the zeolite framework is established that takes into account the influence of modulus as well as temperature. Here the kinetic of the solid phase reaction is a superposition of two different mechanisms described by the Monod equation.

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Calculation of the hydrothermal long-term stability of zeolites in gas-desulphurization and gas-drying processes

Cited by 20 publications

References 9 publications

Sulfur Dioxide Sorption Properties and Thermal Stability of Hydrophobic Zeolites

Sulfur Dioxide Sorption Properties and Thermal Stability of Hydrophobic Zeolites

Zeolite (In)Stability under Aqueous or Steaming Conditions

Investigation and Modeling of the Hydrothermal Stability of Technically Relevant Zeolites

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