Influence of the external surface area of small crystallite zeolites on the micropore volume determination

1998 ◽  
Vol 25 (1-3) ◽  
pp. 185-192 ◽  
Author(s):  
Eduardo Falabella Sousa-Aguiar ◽  
Adilson Liebsch ◽  
Beatriz C. Chaves ◽  
Alexandre F. Costa
Keyword(s):  
Surface Area ◽  
External Surface ◽  
Micropore Volume ◽  
External Surface Area ◽  
Volume Determination ◽  
Small Crystallite

Short-Chain alkylammonium montmorillonites and alcohols: gas adsorption and immersional wetting

Clay Minerals ◽  
1989 ◽  
Vol 24 (4) ◽  
pp. 631-647 ◽  
Author(s):  
R. Malberg ◽  
I. Dékány ◽  
G. Lagaly
Keyword(s):  
Surface Area ◽  
Chain Length ◽  
Gas Adsorption ◽  
Alkyl Chain ◽  
External Surface ◽  
Micropore Volume ◽  
Alkyl Chain Length ◽  
Short Chain ◽  
External Surface Area ◽  
Internal Surface Area

AbstractShort-chain alkylammonium derivatives of montmorillonite (< 8 or 10 C atoms in the alkyl chain) adsorb alcohols in the micropores between the alkylammonium ions. The external surface area and the micropore volume are derived from comparison plots of ethanol and butanol adsorption isotherms. The micropore volume varies between ∼0 (decylammonium derivative) and 100µl/g (methylammonium derivative); the external surface area determined by ethanol and butanol gas adsorption is about 50 m2/g, and is almost independent of the alkyl chain length. In contact with the alcohols, the alkylammonium ions in the interlayer space remain in h1 or h2 arrangement (monolayers or bilayers of flat-lying alkylammonium ions); on the external surface they move into an upward position. The heat of immersion decreases strongly with increasing alkyl chain length to a minimum for decylammonium ions, the variation being very similar for ethanol, butanol, hexanol, octanol and decanol. Immersion in ethanol increases the external surface area at the expense of the internal surface area. In butanol and longer alcohols this area remains unchanged. The increase of the external surface is related mainly to changes in the less ordered regions around the core of the crystals which consists of coherent silicate layers. The heat of wetting is ∼ 110 mJ/m2 (external and internal surfaces). The integral enthalpy of adsorption of butanol, 40–50 kJ/mol, is independent of the alkyl chain length (nc ≤ 8).

scholarly journals Photocatalytic Activity inCH3CN Related to the Surface Properties ofTiO2Powders Prepared by Sol-Gel Method

2009 ◽  
Vol 2009 ◽  
pp. 1-6 ◽  
Author(s):  
Marta Bettoni ◽  
Pietro Candori ◽  
Fabio Marmottini ◽  
Nicoletta Perenze ◽  
Cesare Rol ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Surface Area ◽  
External Surface ◽  
Sol Gel ◽  
Micropore Volume ◽  
Bet Surface Area ◽  
External Surface Area ◽  
Test Reaction ◽  
Gel Method ◽  
Sol Gel Method

SomeTiO2powders, prepared from titanium(IV)tetraisopropoxide by the sol-gel method and thermally treated between 100 and1000∘C, have been characterized by X-ray powder diffraction and by nitrogen adsorption and desorption at 77 K to calculate the BET-specific surface area, from which the micropore volume and the external surface area can be derived. The photocatalytic activity (ka) of the above powders has been evaluated considering theTiO2-sensitized photo-oxidation of 4-methoxybenzyl alcohol inCH3CN as the test reaction. The decrease ofkahave been related to the decrease of the BET surface area, the micropore volume, and the external surface area of theTiO2powders, but a satisfactory linear correlation is observed only for the last superficial parameter.

scholarly journals The Amounts of Water Adsorbed to the Surface of Clay Minerals at the Plastic Limit

2017 ◽  
Vol 64 (3-4) ◽  
pp. 155-162
Author(s):  
Aleksandra Gorączko ◽  
Andrzej Olchawa
Keyword(s):  
Surface Area ◽  
External Surface ◽  
Solid Phase ◽  
Water System ◽  
Basal Spacing ◽  
Plastic Limit ◽  
X Ray Diffraction ◽  
External Surface Area ◽  
X Ray ◽  
Water Layers

AbstractThe paper presents results of a study on the amount of water associated with the solid phase of the clay water system at the plastic limit. Two model monomineral clays, namely kaolinite, and montmorillonite, were used in the study. The latter was obtained by gravitational sedimentation of Na-bentonite (Wyoming).The calculated mean number of water molecule layers on the external surface of montmorillonite was 14.4, and water in interlayer spaces constituted 0.3 of the water mass at the plastic limit.The number of water layers on the external surface of kaolinite particles was 63, which was related to the higher density of the surface electrical charge of kaolinite compared to that of montmorillonite.The calculations were made on the basis of the external surface area of clays and the basal spacing at the plastic limit measured by an X-ray diffraction test. The external surface area of clays was estimated by measuring sorption at a relative humidity p/p0 = 0.5.

scholarly journals Plasma Catalysis: Distinguishing between Thermal and Chemical Effects

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 185 ◽  
Author(s):  
Guido Giammaria ◽  
Gerard van Rooij ◽  
Leon Lefferts
Keyword(s):  
Gas Phase ◽  
Surface Area ◽  
Thermal Effects ◽  
External Surface ◽  
Plasma Chemistry ◽  
Internal Surface ◽  
Plasma Power ◽  
External Surface Area ◽  
Internal Surface Area ◽  
Chemical Effects

The goal of this study is to develop a method to distinguish between plasma chemistry and thermal effects in a Dielectric Barrier Discharge nonequilibrium plasma containing a packed bed of porous particles. Decomposition of CaCO3 in Ar plasma is used as a model reaction and CaCO3 samples were prepared with different external surface area, via the particle size, as well as with different internal surface area, via pore morphology. Also, the effect of the CO2 in gas phase on the formation of products during plasma enhanced decomposition is measured. The internal surface area is not exposed to plasma and relates to thermal effect only, whereas both plasma and thermal effects occur at the external surface area. Decomposition rates were in our case found to be influenced by internal surface changes only and thermal decomposition is concluded to dominate. This is further supported by the slow response in the CO2 concentration at a timescale of typically 1 minute upon changes in discharge power. The thermal effect is estimated based on the kinetics of the CaCO3 decomposition, resulting in a temperature increase within 80 °C for plasma power from 0 to 6 W. In contrast, CO2 dissociation to CO and O2 is controlled by plasma chemistry as this reaction is thermodynamically impossible without plasma, in agreement with fast response within a few seconds of the CO concentration when changing plasma power. CO forms exclusively via consecutive dissociation of CO2 in the gas phase and not directly from CaCO3. In ongoing work, this methodology is used to distinguish between thermal effects and plasma–chemical effects in more reactive plasma, containing, e.g., H2.

Surface Area of the Euphausiid Thysanöessa raschii and Its Relation to Body Length, Weight, and Respiration

1977 ◽  
Vol 34 (2) ◽  
pp. 225-231 ◽  
Author(s):  
Gareth C. H. Harding
Keyword(s):  
Oxygen Consumption ◽  
Metabolic Rate ◽  
Surface Area ◽  
Body Length ◽  
External Surface ◽  
Dry Weight ◽  
External Surface Area ◽  
Marine Crustaceans ◽  
Respiratory Surface ◽  
Wet Weight

A method is described for estimating the surface area of marine crustaceans. The external surface area of the euphausiid Thysanöessa raschii (M. Sars) is proportional to length2.4, dry weight0.95, and wet weight0.84. Oxygen consumption is proportional to wet weight0.82, which indicates that respiration should be proportional to respiratory surface area. The implications of this finding regarding the relations of metabolic rate, size, and surface area are discussed in a broader framework by comparing them with similar studies on vertebrates and other invertebrates.

Characteristics and origin of sepiolite (Meerschaum) from Central Somalia

Clay Minerals ◽  
1998 ◽  
Vol 33 (2) ◽  
pp. 349-362 ◽  
Author(s):  
A. Singer ◽  
K. Stahr ◽  
M. Zarei
Keyword(s):  
Chemical Composition ◽  
Surface Area ◽  
External Surface ◽  
High Viscosity ◽  
Dense Network ◽  
External Surface Area ◽  
Random Orientation ◽  
Plateau Region ◽  
Central Plateau ◽  
Closed Basin

AbstractNearly pure sepiolite clay crops out in a playa-like depression near El Bur, Central Plateau region of Somalia. The deposit is associated with the Lower to Mid-Eocene Taleh Formation that includes, besides limestone, dolomite and gypsiferous marls, extensive anhydrite and various evaporites, primarily gypsum. The material was examined by XRD, DTA, IR and EM. The XRD and DTA analyses indicated that from 40 cm down to a depth of 300 cm, the material consists of well crystallized sepiolite, accompanied in some layers by minor calcite and traces of quartz and halite. The chemical composition, determined by XRF, indicated a low-Fe mineral, with the formula: (Si11.888Al0.l12)(Mg7.313Al0.154Fe0.084)O30(OH2)4(OH2)4.x8H2O.The fibres, arranged in the form of interwoven mats, are straight and have lengths varying between 2-6 µm and widths of 20-40 nm. Commonly, they are aggregated into units of two parallel-lying fibres, with a random orientation against each other, creating a dense network of pores. The high viscosity and external surface area (306-346 m2g-1) of the material, compared to those of the Spanish Vallecas sepiolite, suggest the high industrial suitability of this clay. The extent of the deposit is not known. Lithology and geomorphology indicate a lacustrine, closed basin evaporative environment of formation for this deposit. In contrast to the palaeolacustrine environments of formation of Spanish and Turkish sepiolite deposits, the E1 Bur sepiolite apparently is more recent.

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