scholarly journals PREPARATION OF MESOPOROUS TITANIA-SILICA AEROGELS BY CO2 SUPERCRITICAL EXTRACTION

2010 ◽  
Vol 7 (2) ◽  
pp. 121-127
Author(s):  
Silvester Tursiloadi ◽  
Dinie Mansur ◽  
Yeny Meliana ◽  
Ruslan Efendi
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Thermal Evolution ◽  
Anatase Phase ◽  
Sol Gel ◽  
Total Pore Volume ◽  
Acid Catalyst ◽  
Supercritical Extraction ◽  
Average Pore

Stable anatase is attractive because of its notable functions for photocatalysis and photon-electron transfer.  TiO2-nanoparticles dispersed SiO2 wet gels were prepared by hydrolysis of Ti(OC4H9n)4 and Si(OC2H5)4 in a 2-propanol solution with acid catalyst.  The solvent in the wet gels was supercritically extracted using CO2 at 60 oC and 22 Mpa in one-step.  Thermal evolution of the microstructure of the extracted gels (aerogels) was evaluated by XRD measurements, TEM and N2 adsorption measurements. The as-extracted aerogel with a large specific surface area, more than 365 m2g-1, contained anatase nanoparticles, about 5 nm in diameter.  The anatase phase was stable after calcinations at temperatures up to 1000 oC, and BET specific surface area, total pore volume and average pore diameter did not change significantly after calcinations at temperature up to 800 oC.   Keywords: Stable anatase, sol-gel, CO2 supercritical extraction.

scholarly journals THE STABILIZING OF ANATASE AEROGEL AT HIGH TEMPERATURE

2010 ◽  
Vol 4 (2) ◽  
pp. 110-116 ◽  
Author(s):  
Silvester Tursiloadi ◽  
Hiroshi Hirashima
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Anatase Phase ◽  
Total Pore Volume ◽  
Average Pore ◽  
Amorphous Sio2 ◽  
Bet Specific Surface Area ◽  
Sio2 Aerogel

Stable anatase is attractive to its notable functions for photo catalysis and photon-electron transfer.   Stable anatase TiO­2 containing amorphous SiO2 aerogel was prepared by hydrolysis of Ti (OC3H7)4 and Si (OC3H7)4 in a 2-propanol solution with acid catalyst. The solvent in wet gels was supercritically extracted in CO2 at 60 oC and 22 Mpa. Thermal evolutions of the microstructure of the gels were evaluated by TGA-DTA, N2 adsorption and XRD. A stable anatase TiO2 containing amorphous SiO2 aerogel with a BET specific surface area of 365 m2/g and a total pore volume of 0.20 cm3/g was obtained as prepared condition. The anatase phase was stable after calcination up to 1000 oC, and BET specific surface area, total pore volume and average pore diameter did not change significantly after calcination up to 900 oC.   Keywords: Supercritical extraction, sol-gel, aerogel, stable anatase structure

Preparation and Structural Analysis of Magnesium Oxide Aerogels

MRS Advances ◽  
2017 ◽  
Vol 2 (57) ◽  
pp. 3505-3510
Author(s):  
Jiankai Zhang ◽  
Xiaohong Chen ◽  
Ran Liu ◽  
Huaihe Song ◽  
Zhihong Li
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Magnesium Oxide ◽  
Specific Surface Area ◽  
Average Pore Size ◽  
Sol Gel ◽  
Average Pore ◽  
X Ray ◽  
Water As Solvent ◽  
Saxs Analysis

ABSTRACTMagnesium oxide aerogels were made by sol-gel process using magnesium methoxide as precursor, methanol and deionized water as solvent with ethanol supercritical fluid drying. The influences of the different factors on the gel time and the specific surface area of magnesium oxide aerogels were studied, and the structure and morphology were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and X-ray diffraction (XRD), and the Small Angle X-ray Scatter (SAXS) was utilized to determine the fractural structure of the magnesium oxide aerogels. The results show that MgO aerogels belong to the typical mesoporous materials with rich network and highly developed pore structure, and the specific surface area is 904.9 m2/g, the apparent density is 0.055 g/cm3, the average pore size is 19.6 nm. The results of SAXS analysis show that the fractal dimension of the MgO aerogels is 2.32 in high q area which proves the existence of rough surface and pore fractal structure.

Optimization of Experimental Conditions for the Preparation of High Specific Surface Area Bamboo-Based Activated Carbon

2015 ◽  
Vol 1090 ◽  
pp. 154-159
Author(s):  
Sheng Zhou Zhang ◽  
Hong Ying Xia ◽  
Li Bo Zhang ◽  
Jin Hui Peng ◽  
Jian Wu ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Total Pore Volume ◽  
High Specific Surface Area ◽  
Raw Material ◽  
Experimental Conditions ◽  
Average Pore

Bamboo as the raw material is carbonized to prepare high specific surface area activated carbon by microwave heating under nitrogen atmosphere in our present work. Influences of activation agents on the preparation of activated carbon are studied. The results show that activation agents have a significant influence on the preparation of activated carbon. Under the heating time of 15 min, the adsorption capacity of the activated carbon prepared utilizing KOH as activation agent is the best. When the KOH/C ratio is 4, the iodine number and yield of activated carbon are 2298 mg/g and 39.82%, respectively. The BET specific surface area, total pore volume and average pore diameter of activated carbon are 3441 m2/g, 2.093 ml/g and 2.434 nm, respectively. The micropore volume of 1.304 ml/g is 62.30% of total pore volume, indicating that the activated carbon is microporous activated carbon.

scholarly journals Influence of vanadium content on structure and activity of V2O5–ZrO2–SiO2 catalyst for propane dehydrogenation

2021 ◽  
pp. 117-125
Keyword(s):  
Specific Surface ◽  
Vanadium Oxide ◽  
Surface Area ◽  
Specific Surface Area ◽  
Average Pore Size ◽  
Sol Gel ◽  
Tetragonal Zirconia ◽  
Propane Dehydrogenation ◽  
Average Pore ◽  
Zirconium Silicate

In order to create alternative vanadium oxide-supported catalysts for the process of non-oxidative propane dehydrogenation to propylene, we studied the effect of the increased content of vanadium oxide in the V2O5–ZrO2–SiO2 composition on its structure and catalytic properties. Zirconium silicate hydrogel in the form of finished spherical granules with the SiO2 content of more than 50% was prepared by direct sol-gel synthesis from zirconium oxychloride and sodium metasilicate using the droplet coagulation technology. Catalysts were fabricated by impregnation of hydrogel with an aqueous solution of vanadyl sulfate salt, hydrothermal treatment and calcination in air. By using scanning electron microscopy, X-ray diffraction analysis and low-temperature nitrogen adsorption/desorption method, we showed that amorphous samples with a developed mesoporous structure (with the pore diameter of ~6 nm and the specific surface area of ~300 m2 g–1) were formed when the content of the supporting V2O5 on zirconium silicate was 10, 20, 25, and 30 wt.%. In the course of temperature increase in the propane dehydrogenation reaction, the catalyst samples crystallized in the reaction mixture propane–inert gas with the formation of tetragonal zirconia. When the content of V2O5 was 25% or 30%, additional phases of reduced vanadium oxides and traces of the zirconium vanadate phase were formed. After the reaction, the specific surface area of the catalysts decreased significantly and the average pore size of the samples with 25% and 30% V2O5 increased to ~30 nm. The propylene yield reproducibly observed on the samples with 25% and 30% V2O5 was lower than that on the samples with 10% V2O5; however, it remained quite high, which was probably due to the expanded diameter of the pores and the appearance of additional ZrV2O7 sites that are active with respect to the dehydrogenation of light alkane.

Rational synthesis of graphitic porous carbon with high content nitrogen doping via ultra-fast pyrolysis of ZIF-8 for electrochemical capacitor with enhanced performance

2019 ◽  
Vol 12 (06) ◽  
pp. 1951004
Author(s):  
Tie Gao ◽  
Haibo Li
Keyword(s):  
Specific Surface ◽  
Specific Capacitance ◽  
Surface Area ◽  
Specific Surface Area ◽  
Rate Capability ◽  
Total Pore Volume ◽  
High Specific Capacitance ◽  
Superior Performance ◽  
Large Specific Surface Area ◽  
Average Pore

In this work, we proposed an effective strategy to prepare nitrogen-doped popcorn-like porous carbons (NPPCs) via ultra-fast carbonization of zeolitic immidazolate frameworks (ZIFs-8), where the ZIFs-8 acted as carbon precursor as well as the template. The obtained NPPCs possess popcorn-like morphology with large specific surface area of 1243[Formula: see text]m2/g, total pore volume of 1.48[Formula: see text]cm3/g and high nitrogen content. Remarkably, the average pore diameter of NPPCs was 4.72[Formula: see text]nm, indicating the presence of amount substantial mesopores. As the electrode of supercapacitor, the NPPCs revealed a relatively high specific capacitance of 610.4[Formula: see text]F/g in KOH (6[Formula: see text]mol/L) at 5[Formula: see text]mV/s. Even the scan rate was increased to 50[Formula: see text]mV/s, an impressive capacity of 424.8[Formula: see text]F/g can be achieved, suggesting good rate capability. Besides, it exhibited outstanding cycling stability with 93% of specific capacitance retention after 10,000 GCD cycles. Moreover, the NPPCs electrode demonstrated high electrochemical performance and stability by designing the coin-type and flexible supercapacitor. The large specific surface area, abundant accessible mesoporosity and novel nanostructure are account for the superior performance.

scholarly journals Sol-Gel Synthesis of Nonstoichiometric Titanium Dioxide for Photo-Oxidation of Toxic Organic Substances

2020 ◽  
Author(s):  
I. B. Dorosheva ◽  
A. A. Rempel ◽  
A. A. Valeeva ◽  
I. A. Weinstein
Keyword(s):  
Titanium Dioxide ◽  
Specific Surface ◽  
Band Gap ◽  
Surface Area ◽  
Specific Surface Area ◽  
Anatase Phase ◽  
Sol Gel ◽  
Bet Method ◽  
Sol Gel Synthesis ◽  
Toxic Organic Substances

Titanium dioxide (TiO2) was synthesized by sol-gel method at different values of pH = 3, 7, 8, 9, or 10. X-ray phase analysis has shown that in an acid rout, an anatase phase had crystallized, and in an alkaline rout an amorphous phase of TiO2 was achieved. After annealing for 4 hours at 350∘C, all samples were transformed into anatase phase. The particle size in the different samples varies from 7 to 50 nm depending on the pH. The diffuse reflectance spectra revealed a high value of the band gap width in the range from 2.9 to 3.4 eV and its narrowing after annealing to the range from 2.8to 3.1 eV. The specific surface area measured by BET method was changing from 80 up to 140 m2 /g. Keywords: Titanium dioxide, nanostructure, photocatalysis, band gap, specific surface area

Managing Properties of Alumina Based Granules Prepared by Disk (Dished) Molding

2019 ◽  
Vol 19 (2) ◽  
pp. 132-141 ◽  
Author(s):  
V. Yu. Kruglyakov ◽  
A. V. Glazyrin ◽  
L. A. Isupova
Keyword(s):  
Mechanical Strength ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Total Pore Volume ◽  
Mesopore Volume ◽  
Average Pore ◽  
Wood Meal ◽  
Highly Active ◽  
Average Size

Alumina-based spherical granules were prepared by disk granulation. Products of gibbsite thermoactivation in various reactors were used as the initial materials. In the course of molding, combustible additives (starch, carbon, wood meal) were added to the thermoactivated gibbsite powder, and NaOH (10 %), C2H5OH (15 %), Н3ВО3(6 %) to the wetting solution (H2O). With the product of centrifugal thermoactivation of hydrargillite, the prepared granules were stronger at the larger average size of pores; addition of NaOH, C2H5OH and H3BO3led to an increase in the specific surface area and micropore proportion but had different effects on the mechanical strength of the granules. Introduction of combustible additives (wood meal, activated carbon) affected only slightly the specific surface area, favored an increase in the total pore volume and mesopore volume, resulted in a decrease in bulk density and mechanical strength of the granules. Conditions were determined for preparation of a highly effective strong dessicant with large specific surface area (up to 340 m2/g) and average pore diameter up to 3.4 nm. Conditions were determined for preparation of strong ultramacroporous granules that are highly active to the Klaus process.

scholarly journals PREPARATION AND CHARACTERIZATION OF POROUS ALUMINA-TITANIA AEROGEL VIA CO2 SUPERCRITICAL EXTRACTION

2010 ◽  
Vol 4 (3) ◽  
pp. 149-155 ◽  
Author(s):  
Silvester Tursiloadi ◽  
Hiroaki Imai ◽  
Hiroshi Hirashima
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Supercritical Extraction ◽  
Metal Alkoxides ◽  
Average Pore ◽  
X Ray ◽  
Porous Titania ◽  
Hydrolysis Of Metal Alkoxides ◽  
Hydrolysis Of

Porous aerogel of titania-alumina were prepared by hydrolysis of metal alkoxides and supercritical extraction of the solvent.  Monolithic wet-gel of 0.2TiO2-0.8Al2O3, prepared by hydrolysis of metal alkoxides in alcoholic solutions, and the solvent in wet gel was supercritically extracted in CO2 at 60oC and 24Mpa for 2h. Thermal evolutions of the microstructure of the gel were evaluated by differential thermal analysis (TG-DTA), N2 adsorption, scanning electron microscopy and X-ray diffractometer. After calcination at 500oC, the specific surface area of the gel was more than 400m2g-1. The average pore radius of aerogel, about 8nm, was about 50% of that for alumina aerogel, but about 4 times larger than that of the xerogel.  The specific surface area of the aerogel was more than 200m2g-1 after calcination at 800oC. The pore size and pore volume of aerogel hardly decreased after calcinations at 800oC, although those values of the xerogel remarkably decreased after calcination up to 800oC. The thermal stability of the microstructure of porous titania-alumina is improved by supercritical extraction.   Keywords: Oxides, Sol-gel chemistry, X-ray diffraction, Infrared pectroscopy

Fuels Desulphurisation by Adsorbtion on Fe / Bentonite

2017 ◽  
Vol 68 (3) ◽  
pp. 483-486
Author(s):  
Constantin Sorin Ion ◽  
Mihaela Bombos ◽  
Gabriel Vasilievici ◽  
Dorin Bombos
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Pore Diameter ◽  
Adsorption Process ◽  
Continuous System ◽  
Gas Oil ◽  
Average Pore ◽  
Atmospheric Distillation

Desulfurisation of atmospheric distillation gasoline and gas oil was performed by adsorption process on Fe/ bentonite. The adsorbent was characterized by determining the adsorption isotherms, specific surface area, pore volume and average pore diameter. Adsorption experiments of atmospheric distillation gasoline and gas oil were performed in continuous system at 280�320oC, 5 atm and volume hourly space velocities of 1�2 h-1. The efficiency of adsorption on Fe / bentonite was better at desulphurisation of gasoline versus gas oil.

scholarly journals Nanometer Pore Structure Characterization of Taiyuan Formation Shale in the Lin-Xing Area Based on Nitrogen Adsorption Experiments

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 298
Author(s):  
Chenlong Ding ◽  
Jinxian He ◽  
Hongchen Wu ◽  
Xiaoli Zhang
Keyword(s):  
Specific Surface ◽  
Pore Structure ◽  
Surface Area ◽  
Specific Surface Area ◽  
Shale Gas ◽  
Pore Volume ◽  
Ordos Basin ◽  
Total Pore Volume ◽  
Nitrogen Adsorption ◽  
Taiyuan Formation

Ordos Basin is an important continental shale gas exploration site in China. The micropore structure of the shale reservoir is of great importance for shale gas evaluation. The Taiyuan Formation of the lower Permian is the main exploration interval for this area. To examine the nanometer pore structures in the Taiyuan Formation shale reservoirs in the Lin-Xing area, Northern Shaanxi, the microscopic pore structure characteristics were analyzed via nitrogen adsorption experiments. The pore structure parameters, such as specific surface area, pore volume, and aperture distribution, of shale were calculated; the significance of the pore structure for shale gas storage was analyzed; and the main controlling factors of pore development were assessed. The results indicated the surface area and hole volume of the shale sample to be 0.141–2.188 m2/g and 0.001398–0.008718 cm3/g, respectively. According to the IUPAC (International Union of Pure and Applied Chemistry) classification, mesopores and macropores were dominant in the pore structure, with the presence of a certain number of micropores. The adsorption curves were similar to the standard IV (a)-type isotherm line, and the hysteresis loop type was mainly similar to H3 and H4 types, indicating that most pores are dominated by open type pores, such as parallel plate-shaped pores and wedge-shaped slit pores. The micropores and mesopores provide the vast majority of the specific surface area, functioning as the main area for the adsorption of gas in the shale. The mesopores and macropores provide the vast majority of the pore volume, functioning as the main storage areas for the gas in the shale. Total organic carbon had no notable linear correlation with the total pore volume and the specific surface area. Vitrinite reflectance (Ro) had no notable correlation with the specific surface area, but did have a low “U” curve correlation with the total pore volume. There was no relationship between the quartz content and specific surface area and total pore volume. In addition, there was no notable correlation between the clay mineral content and total specific surface area and total pore volume.

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