Heterogeneous Interactions of Methylamines on porous Adsorbents Part II. Interactions on Silica–Alumina and Silica Gel Surfaces of Di- and Tri-methylamine in the Region of their Boiling Points

1972 ◽  
Vol 50 (15) ◽  
pp. 2451-2456 ◽  
Author(s):  
W. G. Cook ◽  
R. A. Ross
Keyword(s):  
Silica Gel ◽  
Surface Coverage ◽  
Adsorbed Layer ◽  
Silica Gels ◽  
Heats Of Adsorption ◽  
Boiling Points ◽  
Silica Alumina ◽  
Desorption Isotherms ◽  
Adsorption Desorption ◽  
Heterogeneous Interactions

The adsorption of di- and tri-methylamine has been studied at 280 and 276°K, respectively, on a range of silica gels and on silica–alumina. Adsorption–desorption isotherms and isothermal calorimetric heats of adsorption were measured. Heats of adsorption for di-methylamine on silica gel varied from 29.0 kcal/mol at θ = 0.05 to 12.0 kcal/mol at monolayer completion, while for silica–alumina the heats fell from 31.4 to 9.0 kcal/mol between these same values of surface coverage. For tri-methylamine on silica gel, heats fell from 21.0, θ = 0.05, to 10.3 kcal/mol, θ = 1.00, while heats of 21.4 and 9.9 kcal/mol, respectively, were found at these same surface coverages on silica–alumina. The values of the heats of adsorption are discussed in terms of interactions in the adsorbed layer which are believed to be influenced by the pore sizes in the adsorbent and by the basicity of the amine molecules.

Heterogeneous Interactions of Methylamines on Porous Adsorbents. Part I. The Adsorption of Monomethylamine on Silica Gels and Silica–Alumina

1972 ◽  
Vol 50 (11) ◽  
pp. 1666-1674 ◽  
Author(s):  
W. G. Cook ◽  
R. A. Ross
Keyword(s):  
Nitrogen Adsorption ◽  
Silica Gels ◽  
Heats Of Adsorption ◽  
Surface Areas ◽  
Pore Size Distributions ◽  
Wide Range ◽  
Heat Curve ◽  
Silica Alumina ◽  
Adsorption Heats ◽  
Adsorption Desorption

The adsorption of monomethylamine has been studied near its boiling point, 266 °K, on silica–alumina and on a wide range of silica gels by measurement of adsorption–desorption isotherms and isothermal calorimetric heats of adsorption. In addition, surface areas and pore-size distributions have been determined by low-temperature nitrogen adsorption. Heats of adsorption on Davison "923" silica gel varied from around 33.0 kcal/mol at θ = 0.01 to 6.2 kcal/mol at monolayer completion. Maxima were observed in this heat curve in the regions of θ = 0.15, 0.28, and 0.40. These phenomena are believed to be related to interactions among the adsorbed species in pores of diameters approaching molecular dimensions. Heats of adsorption on silica–alumina fell smoothly from 39.5 kcal/mol at θ = 0.03 to 13.0 kcal/mol at θ = 1.00. Adsorption–desorption characteristics of methylamine were also examined on a series of silica gels with widely different pore structures. The variations in the heats of adsorption with surface coverage are discussed in terms of both the nature of the adsorbed surface species and lateral interactions among the adsorbed molecules.

Low Surface Coverage Interactions of Sulfur Dioxide on Selected Transition Metal Catalysts from 273 to 423 °K

1971 ◽  
Vol 49 (17) ◽  
pp. 2832-2839 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Transition Metal ◽  
Silica Gel ◽  
Surface Coverage ◽  
Nitrogen Adsorption ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Hydrogen Bond Formation ◽  
Support Medium ◽  
Adsorption Desorption

Calorimetric beats of adsorption for sulfur dioxide at low surface coverages from 0.004 to 0.600 μmol m−2 on a number of supported transition metal catalysts have been measured between 273 and 423 °K mainly by an adiabatic technique. The catalysts included Fe2O3, Mn2O3, V2O5, MnSO4, and "NiS" ail supported on silica gel.Sulfur dioxide adsorption/desorption isotherms, nitrogen adsorption data, and chemical and infrared analyses were also determined to provide further ancillary information.Heats of adsorption at 423 °K for adsorbed amounts of 0.004 μmol m−2 varied with the adsorbent from nearly 39.0 for Mn2O3 on silica gel to 23.0 kcal mol−1 for the silica gel support medium. With increase in surface coverage to 0.600 μmol m−2 the heat values begin to steady at 6 to 7, 7 to 8, and 8 to 9 kcal mol−1 at 423, 373, and 323 °K, respectively, and less discrimination is observed among the various materials. Preadsorption of small amounts of sulfur dioxide on the supported oxides followed by oxygen admission caused sharp initial falls of as much as 7 to 8 kcal mol−1 in the heat values whereas preadsorption of oxygen followed by sulfur dioxide gave only slight heat increases of around 1 kcal mol−1.It is proposed that sulfur dioxide is chemisorbed on all surfaces with the strongest interactions occurring at the lowest coverages. Sulfates are formed on the oxides as confirmed by chemical analysis, and it is postulated that multiple hydrogen bond formation occurs on silica gel through the interaction of sulfur dioxide oxygen atoms with surface hydroxy groups.

Sorption of dimethyl ether on silica gel

1970 ◽  
Vol 48 (1) ◽  
pp. 13-16 ◽  
Author(s):  
E. Robinson ◽  
R. A. Ross
Keyword(s):  
Dimethyl Ether ◽  
Hysteresis Loops ◽  
Acid Sites ◽  
Silica Gels ◽  
Hydrogen Bond Formation ◽  
Heats Of Adsorption ◽  
Heat Treated ◽  
Ether Oxygen ◽  
Initial Adsorption ◽  
Adsorption Desorption

The adsorption of dimethyl ether has been studied at its boiling point on a range of silica gels by measurement of adsorption/desorption isotherms and isothermal calorimetric heats of adsorption. Data were determined on gels heat treated at 240, 500, 700, and 900 °C and also on gels impregnated with 0.274% w/w aluminum. On 240 °C gels, heats of adsorption varied from around 20 through 12 to 7 kcal/mole at θ = 0.01, 0.50, and 0.90, respectively. Hysteresis loops are analyzed and the initial adsorption trends explained by hydrogen bond formation between the ether oxygen and surface hydroxy groups. The enhanced amounts of ether adsorbed after aluminum impregnation are explained by the creation of either Brønsted acid sites on gels treated at 240 °C or Lewis acid sites on gels treated at the highest temperatures.

Heterogeneous Interactions of Methylamines on Porous Adsorbents. Part III. The Adsorption Characteristics of Methylamines on γ-alumina and Types '3A' and '13X' 'Molecular Sieves'

1973 ◽  
Vol 51 (4) ◽  
pp. 533-537 ◽  
Author(s):  
Walter George Cook ◽  
Robert Anderson Ross
Keyword(s):  
Adsorption Isotherms ◽  
Molecular Sieves ◽  
Heats Of Adsorption ◽  
Adsorption Characteristics ◽  
Boiling Points ◽  
Porous Adsorbents ◽  
Low Pressures ◽  
Heterogeneous Interactions ◽  
Monolayer Coverage

The adsorption characteristics of mono-, di-, and trimethylamine on γ-alumina have been investigated and adsorption isotherms in the regions of their boiling points determined, along with isothermal calorimetric heats of adsorption up to monolayer coverage (θ = 1). From the initial heats of adsorption of 21.6 to 32.4 kcal/mol θ = 0.05, and the strong retention of the amines adsorbed at low pressures, chemisorption is considered to occur at θ < 0.20. The maxima and minima displayed in the heat curves are discussed in terms of adsorbate–adsorbate interactions at sub-monolayer coverage levels. Adsorption isotherms for di-and tri-methylamine on Linde 'molecular sieves' '13X' and '3A' have been measured also, along with the trimethylamine heat curves for these materials.

The Effect of Heat Treatment of Silica Gels on the Calorimetric Heats of Adsorption of Sulfur Dioxide up to One-twentieth Monolayer Coverage at 423 °K

1972 ◽  
Vol 50 (8) ◽  
pp. 1241-1245 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Nitrogen Adsorption ◽  
Silica Gels ◽  
Distribution Data ◽  
Heats Of Adsorption ◽  
Heat Treated ◽  
Adsorbed Complex ◽  
Adsorption Desorption ◽  
Limiting Values ◽  
Dual Site

Calorimetric heats of adsorption of sulfur dioxide have been determined at 423°K for a series of silica gels heat-treated at 240, 550, 700, 800, and 900 °C. At the lowest surface coverage of 0.01 μmol m−2, heats of 25 to 30 kcal mol−1 were observed. These values dropped rapidly with increasing coverage and approached "limiting" values of 6 to 7 and 12 kcal mol−1 for dehydroxylated and hydroxylated surfaces, respectively. To explain the results at lowest coverages an adsorbed complex involving multiple hydrogen bonds is proposed while at higher coverages it is suggested that single and dual site adsorbed species predominate for the dehydroxylated and hydroxylated surfaces, respectively. Sulfur dioxide adsorption isotherms on all gels at 423 °K obeyed the Langmuir equation.Adsorbents were characterized by nitrogen adsorption–desorption isotherms at 77 °K and pore size distribution data were calculated from the desorption branch.

scholarly journals Effect of Hydrophobic Silica Nanochannel Structure on the Running Speed of a Colloidal Damper

2021 ◽  
Vol 11 (15) ◽  
pp. 6808
Author(s):  
Gengbiao Chen ◽  
Zhiwen Liu
Keyword(s):  
Fractal Dimension ◽  
Silica Gel ◽  
Fractal Theory ◽  
Percolation Model ◽  
Silica Gels ◽  
Practical Significance ◽  
Running Speed ◽  
Fractal Percolation ◽  
Micropore Structure ◽  
Hydrophobic Silica

A colloidal damper (CD) can dissipate a significant amount of vibrations and impact energy owing to the interface power that is generated when it is used. It is of great practical significance to study the influence of the nanochannel structure of hydrophobic silica gel in the CD damping medium on the running speed of the CD. The fractal theory was applied to observe the characteristics of the micropore structure of the hydrophobic silica gel by scanning electron microscopy (SEM), the primary particles were selected to carry out fractal analysis, and the two-dimensional fractal dimension of the pore area and the tortuous fractal dimension of the hydrophobic silica gel pore structure were calculated. The fractal percolation model of water in hydrophobic silica nanochannels based on the slip theory could thus be obtained. This model revealed the relationship between the micropore structure parameters of the silica gel and the running speed of the CD. The CD running speed increases with the addition of grafted molecules and the reduction in pore size of the silica gel particles. Continuous loading velocity testing of the CD loaded with hydrophobic silica gels with different pore structures was conducted. By comparing the experimental results with the calculation results of the fractal percolation model, it was determined that the fractal percolation model can better characterize the change trend of the CD running velocity for the first loading, but the fractal dimension was changed from the second loading, caused by the small amount of water retained in the nanochannel, leading to the failure of fractal characterization.

scholarly journals Extraction and Mass Spectrometric Characterization of Terpenes Recovered from Olive Leaves Using a New Adsorbent-Assisted Supercritical CO2 Process

Foods ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1301
Author(s):  
Zully J. Suárez Montenegro ◽  
Gerardo Álvarez-Rivera ◽  
Jose A. Mendiola ◽  
Elena Ibáñez ◽  
Alejandro Cifuentes
Keyword(s):  
Aluminum Oxide ◽  
Silica Gel ◽  
Supercritical Co2 ◽  
Olive Leaves ◽  
Fractionation Process ◽  
Selective Enrichment ◽  
Adsorption Desorption ◽  
First Time ◽  
By Products

This work reports the use of GC-QTOF-MS to obtain a deep characterization of terpenoid compounds recovered from olive leaves, which is one of the largest by-products generated by the olive oil industry. This work includes an innovative supercritical CO2 fractionation process based on the online coupling of supercritical fluid extraction (SFE) and dynamic adsorption/desorption for the selective enrichment of terpenoids in the different olive leaves extracts. The selectivity of different commercial adsorbents such as silica gel, zeolite, and aluminum oxide was evaluated toward the different terpene families present in olive leaves. Operating at 30 MPa and 60 °C, an adsorbent-assisted fractionation was carried out every 20 min for a total time of 120 min. For the first time, GC-QTOF-MS allowed the identification of 40 terpenoids in olive leaves. The GC-QTOF-MS results indicate that silica gel is a suitable adsorbent to partially retain polyunsaturated C10 and C15 terpenes. In addition, aluminum oxide increases C20 recoveries, whereas crystalline zeolites favor C30 terpenes recoveries. The different healthy properties that have been described for terpenoids makes the current SFE-GC-QTOF-MS process especially interesting and suitable for their revalorization.

scholarly journals Synthesis and Characterization of Nanoporous Monetite Which Can Be Applicable for Drug Carrier

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Esmael Salimi ◽  
Jafar Javadpour
Keyword(s):  
Surface Area ◽  
Cetyltrimethylammonium Bromide ◽  
Drug Carrier ◽  
Synthesis And Characterization ◽  
X Ray ◽  
Plate Shape ◽  
Desorption Isotherms ◽  
Adsorption Desorption

Wormhole-like mesostructured monetite was successfully synthesized using cetyltrimethylammonium bromide (C19H42BrN, CTAB), as a porosity agent. X-ray techniques and FTIR reveal that the crystalline grains consist of highly crystalline pure monetite phase. Monetite rods with diameter around 20–40 nm and length in the range of 50–200 nm were confirmed by FESEM and TEM. Based on N2adsorption-desorption isotherms investigation, surface area increased up to 31.5 m2/g due to the removal of surfactant after calcinations at 400°C. The results indicate that CTAB can not only affect monetite crystallization but also change particles morphology from plate shape to rod-like.

Characterization of mesoporous region by the scanning of the hysteresis loop in adsorption–desorption isotherms

Adsorption ◽  
2021 ◽  
Author(s):  
C. F. Toncón-Leal ◽  
J. Villarroel-Rocha ◽  
M. T. P. Silva ◽  
T. P. Braga ◽  
K. Sapag
Keyword(s):  
Hysteresis Loop ◽  
Desorption Isotherms ◽  
Adsorption Desorption
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