The Influence of Physical and Chemical Properties of Alumina on Hydrogen Fluoride Adsorption

Coyne, J. F.; Wainwright, Mark; Brungs, M. P.; Bagshaw, A.N.

doi:10.1007/978-3-319-48176-0_108

Cited by 3 publications

(5 citation statements)

References 3 publications

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“…Key properties are given in Table 1 with isotherms in Figure 3; clearly, both possess very similar BET SSAs, a parameter which is used to quantify the adsorption capacity of a range of adsorbates, including smelter grade alumina. 7,22,26,27 Similarly, average pore diameters are also quite similar in spite of the clearly different pore size distributions. PSDs of each alumina following recycling through an industrial dry scrubber are also provided.…”

Section: Resultsmentioning

confidence: 80%

“…Several models exist which consider the formation of uniform mono-or multilayer adsorbate films hydrogen bonded to surface hydroxyl groups, or to the oxide surface in interactions mediated by adsorbed water molecules. 19,21,22 Previous work has even provided an estimate of monolayer site areas, at 3.3−5.4 Å 2 , corresponding to layer thicknesses (the diameter of an assumed spherical adsorbate) of 0.65−0.83 nm. 21 This work attempts to understand changes in the pore structure of aluminas on interaction with HF from which insights into the aging of these materials and nature of the alumina−HF interaction may be gained.…”

Section: Introductionmentioning

confidence: 99%

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Adsorptive Capacity and Evolution of the Pore Structure of Alumina on Reaction with Gaseous Hydrogen Fluoride

et al. 2015

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Brunauer-Emmet-Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding, that porosity changes are attributed not to monolayer uptake but more reasonably to pore length attenuation. The model assumes nothing specific regarding the Al2O3-HF system and is therefore likely general to adsorbate/adsorbent phenomena.

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Section: Resultsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Adsorptive Capacity and Evolution of the Pore Structure of Alumina on Reaction with Gaseous Hydrogen Fluoride

et al. 2015

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“…It is known that the water sorption capacity of γ-Al 2 O 3 strongly depends on its surface area. 47,48 In contrast to the zeolites mentioned above, both Al 2 O 3 samples exhibit stronger water uptake capability at high temperatures (>300 °C), which explains the high transient activity obtained with Al 2 O 3 -diluted catalysts at 300 °C.…”

Section: Resultsmentioning

confidence: 91%

“…TPD results (Figure C) show that the high-surface-area Al 2 O 3 has larger water sorption capacity than the low-surface-area Al 2 O 3 over the whole temperature range. It is known that the water sorption capacity of γ-Al 2 O 3 strongly depends on its surface area. , In contrast to the zeolites mentioned above, both Al 2 O 3 samples exhibit stronger water uptake capability at high temperatures (>300 °C), which explains the high transient activity obtained with Al 2 O 3 -diluted catalysts at 300 °C.…”

Section: Resultsmentioning

confidence: 91%

Enhanced Catalytic Activity for Methane Combustion through in Situ Water Sorption

et al. 2020

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Although palladium-based materials are efficient catalysts for methane combustion, H2O-poisoning remains a significant problem at low operating temperatures (<450 °C). It is a significant research challenge to find catalysts that can withstand water while delivering rates comparable to the dry PdO phase. Therefore, an in situ water sorption strategy could be advantageous in maintaining high rates for the reaction. Here, we investigate water sorbents that are used to remove the water produced by the reaction, which significantly enhances the activity of a Pd/CeO2 catalyst for methane combustion. The results reveal that the addition of zeolites or alumina to the Pd catalyst can transiently reduce the water concentration in the reactor and thus lead to increased catalytic rates. However, due to the limited number of sorption sites, hydroxylation of the PdO phase takes place rapidly, causing the catalyst to quickly exhibit the same activity as without the sorbent after a transient state. However, by using a stronger sorbent such as CaO mixed with the catalyst, it is possible to obtain higher catalytic activity that is maintained for longer periods of time. This latter system exhibits a 6-fold improvement in transient conversion of methane compared to that of the control catalyst. Meanwhile, long-term stability tests show catalytic activity higher than that without sorbent for extended periods of time. Mechanistic analysis demonstrated that the number of adsorptive sites and the water sorption energy on the sorbents both influenced the water sorption efficiency. Although the sorbent needs to be regenerated, we envision this strategy being useful in conditions where regeneration can be performed without disruption of the catalytic performance. Overall, this work opens an avenue for promoting the methane combustion activity of catalysts by in situ water sorption.

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“…But the adsorption theory may not explain the inhibition and direction-changing effect. Coyne et al 23 reported the adsorbed gluconate ions can only cover 3.5% of seeds surface but can lead to 90% crystallization inhibition. What is more, the boehmite can be also acquired in the appearance of alditols without the induction of boehmite seeds according to Section 3.1.…”

Section: Experimental Methods and Calculationsmentioning

confidence: 99%

Boehmite Preparation via Alditols-Interacting Transformation of Metastable Intermediates in Al–H₂O Reaction Crystallization

Wang

Guo

et al. 2016

Crystal Growth & Design

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Boehmite was prepared efficiently by adding alditols to Al−H 2 O reaction crystallization in moderate condition. We demonstrate that it is the interaction between alditols and metastable intermediates that inhibits the decomposition of aluminate ions into gibbsite and favors the formation of boehmite rather than the blocking of gibbsite growth sites as reported in the previous investigations. The analysis of the crystal formation process shows that the alditols play a role before the nucleation. The interaction simulated by density functional theory and the local hard and soft, acids and bases theory suggests that the metastable intermediates act as soft bases, while the alditols play the role of acids in the interaction, and the higher the alditols' softness, the stronger the inhibiting effect. The configuration of the interacting metastable intermediates and alditols was also verified by the comparison of both experimental and computational Fourier transform infrared spectra.

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The Influence of Physical and Chemical Properties of Alumina on Hydrogen Fluoride Adsorption

Cited by 3 publications

References 3 publications

Adsorptive Capacity and Evolution of the Pore Structure of Alumina on Reaction with Gaseous Hydrogen Fluoride

Adsorptive Capacity and Evolution of the Pore Structure of Alumina on Reaction with Gaseous Hydrogen Fluoride

Enhanced Catalytic Activity for Methane Combustion through in Situ Water Sorption

Boehmite Preparation via Alditols-Interacting Transformation of Metastable Intermediates in Al–H₂O Reaction Crystallization

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The Influence of Physical and Chemical Properties of Alumina on Hydrogen Fluoride Adsorption

Cited by 3 publications

References 3 publications

Adsorptive Capacity and Evolution of the Pore Structure of Alumina on Reaction with Gaseous Hydrogen Fluoride

Adsorptive Capacity and Evolution of the Pore Structure of Alumina on Reaction with Gaseous Hydrogen Fluoride

Enhanced Catalytic Activity for Methane Combustion through in Situ Water Sorption

Boehmite Preparation via Alditols-Interacting Transformation of Metastable Intermediates in Al–H2O Reaction Crystallization

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Boehmite Preparation via Alditols-Interacting Transformation of Metastable Intermediates in Al–H₂O Reaction Crystallization