scholarly journals Kinetic of sintering of polyethilene glycol and lanthanum dopped aluminum oxide obtained by the sol-gel method

2011 ◽  
Vol 65 (4) ◽  
pp. 355-362
Author(s):  
Tatjana Novakovic ◽  
Ljiljana Rozic ◽  
Zorica Vukovic ◽  
Srdjan Petrovic
Keyword(s):  
Heat Treatment ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Initial Period ◽  
Sol Gel ◽  
Textural Properties ◽  
Sintering Behavior ◽  
Isothermal Heat Treatment ◽  
Surface Areas

Sintering and crystallization of low-density polyethylene glycol (PEG) and lanthanum, La(III)-doped Al2O3 aerogels prepared from aluminum isopropoxide were investigated. The sintering behavior of non-doped and doped aerogels was examined by following the change of specific surface area with isothermal heat-treatment. The specific surface area and crystalline phases of non-doped and PEG+La(III)-doped aerogels were determined, and the effects of dopants on the sintering and crystallization of Al2O3 aerogels are discussed. Isothermal sintering experiments showed that the sintering mechanism of non-doped and PEG+La(III)-doped Al2O3 aerogels is surface diffusion. The specific surface areas of alumina samples decrease rapidly during the initial period of sintering, and more slowly with prolonged sintering time. The change of the porous structure is correlated with the phase transformation of ?-Al2O3 during calcinations of Al2O3 aerogels. The surface area of non-doped Al2O3 aerogels came to about 20 m2g-1 with heat-treatment at 1100?C because of crystallization of ?-Al2O3 after densification. In the case of heattreatment at 1200?C, the largest surface area was observed for PEG+La(III) doped Al2O3 aerogels and the XRD pattern showed only low ordered ?-Al2O3. These indicate that the addition of PEG+La(III) to boehmite sol prevents Al2O3 aerogels from sintering and crystallizing to the ?-Al2O3 phase. Even after 20 h at 1000?C, PEG+La (III)-doped alumina samples maintain a rather good specific surface area (108 m2 g-1) in comparison to the non-doped, containing mainly ?-Al2O3 and minor amounts of ?-Al2O3. Aluminum-oxides with these structural and textural properties are widely used as a coatings and catalyst supports in the field of various catalysis.

scholarly journals A Case Study of Waste Scrap Tyre-Derived Carbon Black Tested for Nitrogen, Carbon Dioxide, and Cyclohexane Adsorption

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4445 ◽  
Author(s):  
Zuzana Jankovská ◽  
Marek Večeř ◽  
Ivan Koutník ◽  
Lenka Matějová
Keyword(s):  
Activated Carbon ◽  
Carbon Black ◽  
Specific Surface ◽  
Surface Area ◽  
Sorption Capacity ◽  
Specific Surface Area ◽  
Textural Properties ◽  
Pyrolytic Carbon ◽  
Surface Areas ◽  
Wide Range

Waste scrap tyres were thermally decomposed at the temperature of 600 °C and heating rate of 10 °C·min−1. Decomposition was followed by the TG analysis. The resulting pyrolytic carbon black was chemically activated by a KOH solution at 800 °C. Activated and non-activated carbon black were investigated using high pressure thermogravimetry, where adsorption isotherms of N2, CO2, and cyclohexane were determined. Isotherms were determined over a wide range of pressure, 0.03–4.5 MPa for N2 and 0.03–2 MPa for CO2. In non-activated carbon black, for the same pressure and temperature, a five times greater gas uptake of CO2 than N2 was determined. Contrary to non-activated carbon black, activated carbon black showed improved textural properties with a well-developed irregular mesoporous-macroporous structure with a significant amount of micropores. The sorption capacity of pyrolytic carbon black was also increased by activation. The uptake of CO2 was three times and for cyclohexane ten times higher in activated carbon black than in the non-activated one. Specific surface areas evaluated from linearized forms of Langmuir isotherm and the BET isotherm revealed that for both methods, the values are comparable for non-activated carbon black measured by CO2 and for activated carbon black measured by cyclohexane. It was found out that the N2 sorption capacity of carbon black depends only on its specific surface area size, contrary to CO2 sorption capacity, which is affected by both the size of specific surface area and the nature of carbon black.

Valorization of cellulose-doped lignin: application of cellulose-doped lignin-derived activated carbon in capacitors and investigation of its textural properties and electrochemical performance

2021 ◽  
Author(s):  
Liangcai Wang ◽  
Xin Feng ◽  
Huanhuan Ma ◽  
Jielong Wu ◽  
Yu Chen ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Specific Capacitance ◽  
Surface Area ◽  
Specific Surface Area ◽  
Wall Thickness ◽  
Textural Properties ◽  
Pore Wall ◽  
Surface Areas ◽  
Pore Wall Thickness

Abstract This work provides an idea for efficient and harmless utilization of lignin and further evaluated the textural properties of lignin-derived activated carbon/specific capacitance relationship. The yield of cellulose-doped apricot shell lignin (ASLC) was 30.42%. H3PO4/KOH was used to assist the preparation of ASLC-derived activated carbon (AAC) for capacitors. The specific surface areas of the as-obtained AAC-P-3 and AAC-K-2 were 1475.16 m2/g and 2136.56 m2/g, respectively. The specific capacitances of AAC-P-3 and AAC-K-2 were 169.14 F/g and 236.00 F/g, respectively, upon the current density of 0.50 A/g. In capacitors containing aqueous KOH as the electrolyte, the AR2 (0.983) between specific surface area and specific capacitance was highest, followed by the AR2 (0.978) between Vmicro/Vmeso and specific capacitance, the AR2 (0.975) between pore-wall thickness and specific capacitance. Consequently, the specific capacitances of the AACs depend not only the specific surface area, but also on the Vmicro/Vmeso, pore-wall thickness, and Vmicro.

scholarly journals Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1787
Author(s):  
Simon Carstens ◽  
Ralf Meyer ◽  
Dirk Enke
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Surface Areas ◽  
Alumina Membranes ◽  
Sol Gel Process ◽  
Specific Surface Areas ◽  
Α Al2o3 ◽  
Sol Gel Synthesis

This article combines a systematic literature review on the fabrication of macroporous α-Al2O3 with increased specific surface area with recent results from our group. Publications claiming the fabrication of α-Al2O3 with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA α-Al2O3 is given, including hydrothermal methods, pore protection approaches, dopants, anodically oxidized alumina membranes, and sol-gel syntheses. Furthermore, limitations of these routes are disclosed, as thermodynamic calculations suggest that γ-Al2O3 may be the more stable alumina modification for ABET > 175 m2/g. In fact, the highest specific surface area unobjectionably reported to date for α-Al2O3 amounts to 16–24 m2/g and was attained via a sol-gel process. In a second part, we report on some of our own results, including a novel sol-gel synthesis, designated as mutual cross-hydrolysis. Besides, the Mn-assisted α-transition appears to be a promising approach for some alumina materials, whereas pore protection by carbon filling kinetically inhibits the formation of α-Al2O3 seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders.

Aerosol-Assisted Sol-Gel Synthesis of Mesoporous TiO2 Materials, and Their Use as Support for Ru-Based Methanation Catalysts

2019 ◽  
Author(s):  
Ara Kim ◽  
Clément Sanchez ◽  
Bernard Haye ◽  
Cédric Boissière ◽  
Capucine Sassoye ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Self Assembly ◽  
Sol Gel ◽  
Textural Properties ◽  
High Specific Surface Area ◽  
Spherical Particles ◽  
Aerosol Process ◽  
Evaporation Induced Self Assembly

<div>Mesoporous TiO<sub>2</sub> materials have been prepared by an aerosol process, which leverages on the acetic acid-mediated sol-gel chemistry and on the evaporation-induced self-assembly phenomenon to obtain materials with high specific surface area and large mesoporous volume. The obtained spherical particles are calcined to release the porosity. It is shown that the mesoscopic order can be preserved when the calcination is carried out at relatively low temperature (375 °C and below). Harsher calcination conditions lead to the progressive destruction of the mesostructured, concomitant with a progressive drop of textural properties and with the crystallization of larger anatase domains. The mesoporous TiO<sub>2</sub> material calcined at 350°C (specific surface area = 260 m².g<sup>-1</sup>; pore volume = 0.36 cm³.<sup>-1</sup>; mean pore diameter = 5.4 nm) was selected as a promising support for preformed RuO<sub>2</sub> nanoparticles, and subsequently annealed in air. It is shown that the presence of RuO<sub>2</sub> nanoparticles and subsequent annealing provoke further intense modification of the texture and crystallinity of the TiO<sub>2</sub> materials. In addition to a drop in the textural parameters, a RuO<sub>2</sub>-mediated crystallization of rutile TiO<sub>2</sub> is highlighted at temperature as low as 250°C. After an in situ reduction in H<sub>2</sub>, the catalysts containing TiO<sub>2</sub> rutile and relatively small RuO<sub>2</sub> crystals showed the highest activity in the methanation of CO<sub>2</sub>. </div>

Aerosol-Assisted Sol-Gel Synthesis of Mesoporous TiO2 Materials, and Their Use as Support for Ru-Based Methanation Catalysts

2019 ◽  
Author(s):  
Ara Kim ◽  
Clément Sanchez ◽  
Bernard Haye ◽  
Cédric Boissière ◽  
Capucine Sassoye ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Self Assembly ◽  
Sol Gel ◽  
Textural Properties ◽  
High Specific Surface Area ◽  
Spherical Particles ◽  
Aerosol Process ◽  
Evaporation Induced Self Assembly

<div>Mesoporous TiO<sub>2</sub> materials have been prepared by an aerosol process, which leverages on the acetic acid-mediated sol-gel chemistry and on the evaporation-induced self-assembly phenomenon to obtain materials with high specific surface area and large mesoporous volume. The obtained spherical particles are calcined to release the porosity. It is shown that the mesoscopic order can be preserved when the calcination is carried out at relatively low temperature (375 °C and below). Harsher calcination conditions lead to the progressive destruction of the mesostructured, concomitant with a progressive drop of textural properties and with the crystallization of larger anatase domains. The mesoporous TiO<sub>2</sub> material calcined at 350°C (specific surface area = 260 m².g<sup>-1</sup>; pore volume = 0.36 cm³.<sup>-1</sup>; mean pore diameter = 5.4 nm) was selected as a promising support for preformed RuO<sub>2</sub> nanoparticles, and subsequently annealed in air. It is shown that the presence of RuO<sub>2</sub> nanoparticles and subsequent annealing provoke further intense modification of the texture and crystallinity of the TiO<sub>2</sub> materials. In addition to a drop in the textural parameters, a RuO<sub>2</sub>-mediated crystallization of rutile TiO<sub>2</sub> is highlighted at temperature as low as 250°C. After an in situ reduction in H<sub>2</sub>, the catalysts containing TiO<sub>2</sub> rutile and relatively small RuO<sub>2</sub> crystals showed the highest activity in the methanation of CO<sub>2</sub>. </div>

scholarly journals Synthesis of Monolithic TiO2 Aerogels With Relatively Low Shrinkage and Improved Formability Assisted by CTAB

2021 ◽  
Vol 8 ◽  
Author(s):  
Tingting Niu ◽  
Bin Zhou ◽  
Zehui Zhang ◽  
Jianming Yang ◽  
Xiujie Ji ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Supercritical Drying ◽  
High Specific Surface Area ◽  
Structure Property ◽  
Surface Areas ◽  
Polycondensation Process

Monolithic TiO2 aerogels without severe shrink were obtained by the sol-gel method with the addition of the surfactant cetyltrimethylammonium bromide (CTAB) to control the hydrolysis and polycondensation process and acetonitrile solvent as the solvent to improve the crystallinity. After CO2 supercritical drying, the shrinkage ratio of monolithic TiO2 aerogels modified by CTAB decreased by up to ∼26.9%, compared with the pure TiO2 aerogel. Their apparent densities were all lower than 300 g/cm3. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform infrared spectroscopy (FTIR) and BET Specific Surface Area Analysis were used to analyze the as-synthesized samples. The results revealed that all the samples were anatase-TiO2 phase with nanoporous network structures. The specific surface areas reached 250.2 m2/g confirmed by the BET (Brunaur–Emmett–Teller method) analysis. However, TiO2 aerogels without the addition of CTAB showed evident agglomeration and collapse of the network in comparison with CTAB-added samples. To further study the structure-property relationship, the photocatalysis performance of as-synthesized and 300°C-calcined aerogels was carried out contrastively. Interestingly, the influences of the CTAB adding amount of as-synthesized and calcined TiO2 aerogels are negative and positive, respectively, which is probably due to the synergistic effect of CTAB hindrance and grain refinement. Potentially, This kind of TiO2 aerogels assisted by CATB with low density, small shrinkage, improved formability, high specific surface area and fine crystalline grain may be applied in various applications, such as electrochemistry, photocatalysis, etc.

scholarly journals Tuning the Morphological Properties of Cellulose Aerogels: An Investigation of Salt-Mediated Preparation

2021 ◽  
Author(s):  
Prakash Parajuli ◽  
Sanjit Acharya ◽  
Julia Shamshina ◽  
Noureddine Abidi
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Earth Metal ◽  
Morphological Properties ◽  
Cellulose Solution ◽  
Bet Analysis ◽  
Sol Gel Transition ◽  
Gel Transition

Abstract In this study, alkali and alkaline earth metal chlorides with different cationic radii (LiCl, NaCl, and KCl, MgCl2, and CaCl2) were used to gain insight into the behavior of cellulose solutions in the presence of salts. The specific focus of the study was evaluation of the effect of salts’ addition on the sol-gel transition of the cellulose solutions and on their ability to form monoliths, as well as evaluation of the morphology (e.g., specific surface area, pore characteristics, and microstructure) of aerocelluloses prepared from these solutions. The effect of the salt addition on the sol-gel transition of cellulose solutions was studied using rheology, and morphology of resultant aerogels was evaluated by Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis, while the salt influence on the aerocelluloses’ crystalline structure and thermal stability was evaluated using powder X-Ray Diffraction (pXRD) and Thermogravimetric Analysis (TGA), respectively. The study revealed that the effect of salts’ addition was dependent on the component ions and their concentration. The addition of salts in the amount below certain concentration limit significantly improved the ability of the cellulose solutions to form monoliths and reduced the sol-gel transition time. Salts of lower cationic radii had a greater effect on gelation. However, excessive amount of salts resulted in the formation of fragile monoliths or no formation of gels at all. Analysis of surface morphology demonstrated that the addition of salts resulted in a significant increase in porosity and specific surface area, with salts of lower cationic radii leading to aerogels with much larger (~1.5 and 1.6-fold for LiCl and MgCl2, respectively) specific surface area compared to aerocelluloses prepared with no added salt. Thus, by adding the appropriate salt into the cellulose solution prior to gelation, the properties of aerocelluloses that control material’s performance (specific surface area, density, and porosity) could be tailored for a specific application.

scholarly journals Synthesis of Spherical Silica by Sol-Gel Method and Its Application as Catalyst Support

2011 ◽  
Vol 10 (2) ◽  
pp. 25
Author(s):  
Anirut Leksomboon ◽  
Bunjerd Jongsomjit
Keyword(s):  
Particle Size ◽  
Ethylene Glycol ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Weight Ratio ◽  
Gel Method ◽  
Sol Gel Method ◽  
Spherical Silica

In this present study, the spherical silica support was synthesized from tetraethyloxysilane (TEOS), water, sodium hydroxide, ethylene glycol and n-dodecyltrimethyl ammonium bromide (C12TMABr). The particle size was controlled by variation of the ethylene glycol co-solvent weight ratio of a sol-gel method preparation in the range of 0.10 to 0.50. In addition, the particle size apparently increases with high weight ratio of co-solvent, but the particle size distribution was broader. The standard deviation of particle diameter is large when the co-solvent weight ratio is more than 0.35 and less than 0.15. However, the specific surface area was similar for all weight ratios ranging from 1000 to 1300 m2/g. The synthesized silica was spherical and has high specific surface area. The cobalt was impregnated onto the obtained silica to produce the cobalt catalyst used for CO2 hydrogenation.</

Photocatalytic Efficiency for Dye Decolorization of the UV/TiO2, UV/TiO2 + In2O3 and UV/TiO2-In2O3 Systems

2013 ◽  
Vol 831 ◽  
pp. 263-266
Author(s):  
Chung Hsin Wu ◽  
Chao Yin Kuo ◽  
Chih Hao Lai ◽  
Wei Yang Chung
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Dye Decolorization ◽  
X Ray Diffraction ◽  
First Order ◽  
First Order Kinetics ◽  
Vis Spectroscopy ◽  
Reactive Red 2

This study explored the decolorization of C.I. Reactive Red 2 (RR2) by the ultraviolet (UV)/TiO2, UV/TiO2 + In2O3, and UV/TiO2-In2O3 systems. The TiO2-In2O3 was generated by the sol-gel method and TiO2 + In2O3 was created by mixing TiO2 and In2O3 powders. The surface properties of TiO2, In2O3, and TiO2-In2O3 were analyzed by X-ray diffraction, a specific surface area analyzer, UV-vis spectroscopy, and scanning electron microscopy. The specific surface area of TiO2, In2O3, and TiO2-In2O3 was 29.5, 44.6, and 35.7 m2/g, respectively; additionally, the band gap of TiO2, In2O3, and TiO2-In2O3 was 2.95, 2.64, and 2.91 eV; respectively. The decolorization rate constant fit pseudo-first-order kinetics and that of the UV/TiO2, UV/TiO2 + In2O3, and UV/TiO2-In2O3 systems was 0.0023, 0.0031, and 0.0072 min-1; respectively.

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