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.

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.

Surface Studies of Heat-treated γ-Aluminas in the Adsorption of Sulfur Dioxide below Monolayer Coverage

1972 ◽  
Vol 50 (16) ◽  
pp. 2537-2543 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Cross Sections ◽  
Nitrogen Adsorption ◽  
High Energy ◽  
Spherical Particles ◽  
Defect Centers ◽  
Heat Treated ◽  
Adsorption Desorption ◽  
Very High ◽  
Monolayer Coverage

Calorimetric heats of adsorption of sulfur dioxide at surface coverages from 0.1 to 3.5 µmol m−2 have been measured on a series of γ-aluminas heat-treated at 500, 700, and 900 °C. Essential features of the structures of the adsorbents have been characterized by analysis of nitrogen adsorption/desorption isotherms and by both direct and indirect electron microscopy.Heats of adsorption of 423 °K for adsorbed amounts of 0.1 µmol m−2 were 48.0, 59.0, and 85.0 kcal mol−1 for the 500, 700 and 900 °C samples, respectively. The values for the 500 and 700 °C samples fell rapidly with increasing coverage to around 19.0 kcal mol−1 at 3.2 to 3.3 µmol m−2, while the values for the 900 °C sample decreased slowly to 15.0 kcal mol−1 at the same coverage.The pores had circular cross sections and mean diameters of 25, 35, and 40 Å were observed for the 500, 700, and 900 °C samples, respectively. Examination of carbon/platinum replicas of the surface showed the presence of agglomerates of spherical particles approximately 400 Å in diameter.It is proposed that the high initial heats on the 500 and 700 °C samples are due to the formation of a sulfate-like species on the surface and at higher coverage extensive hydrogen bonding is present. The very high heats obtained on the 900 °C sample are believed to be due to interactions with high-energy defect centers in the oxide which were created by heat treatment.

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.

Adiabatic Calorimetric Studies of the Adsorption of Sulfur Dioxide at 423 °K on Heat-treated Magnesias Characterized by Electron Microscopy

1972 ◽  
Vol 50 (17) ◽  
pp. 2817-2822 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Nitrogen Adsorption ◽  
High Energy ◽  
Structural Features ◽  
Average Particle ◽  
Cubic Form ◽  
Transmission Electron ◽  
Heat Treated ◽  
Calorimetric Studies ◽  
Adsorption Desorption

Calorimetric heats of adsorption of sulfur dioxide at surface coverages from 0.2 to 7.7 μmol m−2 have been measured on a series of magnesias heat-treated at 600, 700, and 800 °C. Structural features of the adsorbents have been characterized by analysis of nitrogen adsorption–desorption isotherms and by transmission electron microscopy.Heats of adsorption at 423 °K for adsorbed amounts of 0.3 μmol m−2 were respectively, 86.0, 87.0, and 77.0 kcal mol−1 for the 600, 700, and 800 °C samples. The values for the 600 and 700 °C samples fell rapidly above a coverage of 2.0 μmol m−2 to around 44.0 kcal mol−1 at 5.0 to 7.0 μmol m−2, while the values for the 800 °C sample decreased continuously to 39.0 kcal mol−1 at the same coverage.Crystallite shapes tended increasingly towards the cubic form as the temperature of heat-treatment was increased and average particle sizes were 80, 240, and 320 Å for the 600, 700, and 800 °C samples, respectively.It is proposed that the very high heats obtained on all the samples are due to interactions with high-energy defect centers in the oxide and with the formation of magnesium sulfite initially, and magnesium sulfate towards monolayer completion.

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.

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.

Extraction of copper ions using silica gel with chemically modified surface

2008 ◽  
Vol 62 (3) ◽  
Author(s):  
Iwona Rykowska ◽  
Wiesław Wasiak ◽  
Joanna Byra
Keyword(s):  
Solid Phase ◽  
Copper Ions ◽  
Nitrogen Adsorption ◽  
Surface Characteristics ◽  
Silica Gels ◽  
Chemically Modified ◽  
Modified Surface ◽  
Adsorption Desorption ◽  
Post Industrial ◽  
Cp Mas Nmr

AbstractThe applicability of silica gels for the application in solid-phase extraction was tested. Silica was modified with ketoimine groups. Surface characteristics of the modified silica were determined by elemental analysis, NMR spectra of solid phases (29Si CP MAS NMR), analysis of pore size distribution of the silica support, and nitrogen adsorption-desorption. Newly proposed sorbents with ketoimine groups were applied in the preconcentration of trace amounts of the Cu (II) ions from lake water, post-industrial water, and demineralized water unburdened back to the lake.

Study on the Pore Structure of Forsterite Insulating Material

2016 ◽  
Vol 697 ◽  
pp. 119-123 ◽  
Author(s):  
Jian Peng Liu ◽  
Xiao Jun Zhang ◽  
Hong Xi Zhu ◽  
Cheng Ji Deng
Keyword(s):  
Fractal Dimension ◽  
Molten Salt ◽  
Pore Size ◽  
Structural Parameters ◽  
Nitrogen Adsorption ◽  
Raw Material ◽  
Molten Salt Method ◽  
Heat Treated ◽  
Adsorption Desorption ◽  
Different Content

Forsterite insulating materials were prepared by molten salt method using forsterite powder, pulp waste, NaCl and Na2CO3 as raw material. The pore size distribution and pore structural parameters of the sample were studied by nitrogen adsorption-desorption method. The fractal dimension of pore was obtained based on FHH (Frenkel-Halsey-Hill) equation. The results showed that adsorption-desorption isotherm of the sample was identified as type II due to the long-narrow pore with narrow openings. The pore size and fractal dimension decreased with the temperature increased. The maximum pore size was about 2 nm in the sample heated at 1100°C in the condition of different content of molten salt. And optimal thermal insulation performance of the sample were obtained in the sample contained 30 wt% Na2CO3 and heat treated at 1100°C.

Phase Separation in Alkoxy-Derived Silica System Containing Polyacrylamide

2007 ◽  
Vol 1007 ◽  
Author(s):  
Kousuke Kawamoto ◽  
Kazuki Nakanishi ◽  
Teiichi Hanada
Keyword(s):  
Phase Separation ◽  
Sol Gel ◽  
Secondary Phase ◽  
Nitrogen Adsorption ◽  
Silica Gels ◽  
Solvent Exchange ◽  
Scanning Calorimetry ◽  
Heat Treated ◽  
Sol Gel Transition

ABSTRACTBy inducing phase separation parallel to the sol-gel transition of alkoxy-derived silica systems, gels having both macroporous and mesoporous structures can be obtained. Using poly(acrylamide) (PAAm) as a phase-separation inducer, macro/mesoporous silica gels were synthesized. After solvent exchange by water, the size distribution of mesopores of wet gels was evaluated by thermoporometry using a differential scanning calorimetry (DSC). Alternatively, gels were evaporation-dried after solvent exchange by ethanol or water/ethanol, followed by heat-treatment to completely remove volatile and organic components. Characterization of the dried or heat-treated samples was carried out using a scanning electron microscope (SEM) and by nitrogen adsorption measurements. Experimental results showed that the interaction between PAAm and silica is not so strong as the case of polymers having poly(oxyethylene) chains. The contribution of the secondary phase separation within the crosslinking silica-rich phase was suggested to be responsible for the mesopore formation in the PAAm-silica system.

scholarly journals Pore Modification and Phosphorus Doping Effect on Phosphoric Acid-Activated Fe-N-C for Alkaline Oxygen Reduction Reaction

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1519
Author(s):  
Jong Gyeong Kim ◽  
Sunghoon Han ◽  
Chanho Pak
Keyword(s):  
Phosphoric Acid ◽  
Photoelectron Spectroscopy ◽  
Structural Changes ◽  
Electronic States ◽  
Nitrogen Adsorption ◽  
Reduction Reaction ◽  
Phosphorus Doping ◽  
X Ray ◽  
Precious Metal Catalysts ◽  
Adsorption Desorption

The price and scarcity of platinum has driven up the demand for non-precious metal catalysts such as Fe-N-C. In this study, the effects of phosphoric acid (PA) activation and phosphorus doping were investigated using Fe-N-C catalysts prepared using SBA-15 as a sacrificial template. The physical and structural changes caused by the addition of PA were analyzed by nitrogen adsorption/desorption and X-ray diffraction. Analysis of the electronic states of Fe, N, and P were conducted by X-ray photoelectron spectroscopy. The amount and size of micropores varied depending on the PA content, with changes in pore structure observed using 0.066 g of PA. The electronic states of Fe and N did not change significantly after treatment with PA, and P was mainly found in states bonded to oxygen or carbon. When 0.135 g of PA was introduced per 1 g of silica, a catalytic activity which was increased slightly by 10 mV at −3 mA/cm2 was observed. A change in Fe-N-C stability was also observed through the introduction of PA.

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