scholarly journals Synthesis and Physico-Chemical Characterization of CeO2/ZrO2-SO42- Mixed Oxides

2017 ◽  
Vol 56 (2) ◽  
Author(s):  
Juan Manuel Hernández-Enríquez ◽  
Rebeca Silva-Rodrigo ◽  
Ricardo García-Alamilla ◽  
Luz Arcelia García-Serrano ◽  
Brent Edward Handy ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mixed Oxides ◽  
Sol Gel ◽  
Synthesis Method ◽  
Chemical Characterization ◽  
Acid Sites ◽  
Oxide Content ◽  
Physico Chemical

Environmentally friendly solid-acid catalysts CeO<sub>2</sub>/ZrO<sub>2</sub>-SO<sub>4</sub><sup>2-</sup> were prepared by the sol gel method varying CeO<sub>2</sub> content (10, 20 and 30 wt%) and using sulfation <em>in situ</em>, maintaining the sulfate ions amount present in the materials at 20 wt%. ZrO<sub>2</sub> and ZrO<sub>2-</sub>SO<sub>4</sub><sup>2-</sup> were also prepared for comparison proposes using the same synthesis method. The materials were characterized by X-ray diffraction, nitrogen physisorption, potentiometric titration with <em>n</em>-butylamine, decomposition of 2-propanol and <em>n</em>-pentane isomerization. The specific surface area of ZrO<sub>2-</sub>SO<sub>4</sub><sup>2-</sup> was high (160 m<sup>2</sup>/g) compared with the unmodified ZrO<sub>2</sub> (80 m<sup>2</sup>/g), however this area decreased with increasing the CeO<sub>2</sub> content (37-100 m<sup>2</sup>/g). There was no significant effect of CeO<sub>2</sub> on the tetragonal structure of ZrO<sub>2-</sub>SO<sub>4</sub><sup>2-</sup>. The variation of acid sites amount runs parallel to the change of specific surface area. The acid sites amount decreased with increasing cerium oxide content. The decomposition of 2-propanol results fundamentally in the formation of dehydration products such as propylene and diisopropyl ether, both involving acid sites. In addition, a good performance during the <em>n</em>-pentane isomerization was observed for these materials. The selectivity towards isopentane reaches 84% when the Pt/CeO<sub>2</sub>/ZrO<sub>2-</sub>SO<sub>4</sub><sup>2-</sup> catalyst with the highest CeO<sub>2</sub> content was used.

scholarly journals Sol-gel preparation and properties of amorphous iron-containing aluminosilicate

2020 ◽  
Vol 64 (11) ◽  
pp. 102-107
Author(s):  
Lyubov V. Furda ◽  
◽  
Evgeniya A. Tarasenko ◽  
Sofya N. Dudina ◽  
Olga E. Lebedeva ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Active Sites ◽  
Sol Gel ◽  
Reference Sample ◽  
Acid Sites ◽  
Molar Ratio ◽  
Indicator Method ◽  
Gel Preparation

The objective of the present study includes a modification of synthetic aluminosilicate with iron cations and an estimation of the modificator influence at structure and properties of the aluminosilicate. The iron-containing aluminosilicate (Si/Al = 4.72) with an Al/Fe molar ratio of 5:1 was prepared by the sol-gel method at pH = 1-2. Amorphous aluminosilicate (Si/Al = 4.72), which was synthesized by analogous procedure, was applied as a reference sample. By scanning electron microscopy, it was found that the powders had particles of 1-20 micrometers in size. The results of low-temperature adsorption-thermal desorption of nitrogen showed that the modification with Fe3+ ions affected the specific surface area and porosity of the material under study. The iron-containing sample has a higher specific surface area and pore volume comparing to the initial aluminosilicate. The Hammett indicator method was used to evaluate the surface centers of the samples. It was found that the materials under study were characterized by the presence of active sites with pKax values in the range from - 4.4 to 12.8 with a pronounced maximum at pKax = 1.02. For an iron-containing sample, the concentration of acid sites significantly decreases at pKax = 1.02, while at pKax 0.80, 1.03, 2.10, 2.50, 4.10, 5.00, 8.00, and 12.80, an increase in the number of acid sites is observed. The values of the Hammett function are practically the same for the studied samples and characterizes them as materials of medium acidity. For iron-containing aluminosilicate, the larger number of active sites was noted, it amounted to 313.5 mmol/g.

scholarly journals SYNTHESIS, STRUCTURE AND PROPERTIES OF ORGANIC GELS BASED ON LARCH BARK TANNINS AND HY-DROLYSIS LIGNIN

2021 ◽  
pp. 109-122
Author(s):  
Nadezhda Mikhailovna Mikova ◽  
Elena Valentinovna Mazurova ◽  
Ivan Petrovich Ivanov ◽  
Boris Nikolayevich Kuznetsov
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Furfuryl Alcohol ◽  
Lignin Content ◽  
Sol Gel ◽  
Chemical Properties ◽  
Hydrolysis Lignin ◽  
Physico Chemical ◽  
Gel Composition

For the first time, tannin-lignin-formaldehyde and tannin-lignin-furfuryl organic gels were obtained on the basis of larch bark tannins and hydrolysis lignin by sol-gel condensation with formaldehyde and furfuryl alcohol. Their physico-chemical properties were studied by varying the content of lignin (from 5 to 30 wt%) and a fixed mass ratio of polyphenolic substances to the crosslinking reagent (1 : 1.5). With an increase in the lignin content the density of tannin-lignin formaldehyde gels decreases from 0.83 to 0.53 g/ cm3, and that of tannin-lignin-furfuryl gels is from 0.32 to 0.14 g / cm3. According to the FTIR data, the structures of tannin-lignin-formaldehyde and tannin-lignin-furfuryl gels are formed by aromatic fragments cross-linked with methylene and methylene-ether bridges. Scanning electron microscopy shows that the addition of appropriate amounts of lignin to tannins (up to 10 wt% when using formaldehyde and up to 20 wt% when using furfuryl alcohol) promotes the formation of gels with a more developed porous structure. In the case of tannin-lignin-formaldehyde gel, the specific surface area and sorption of methylene blue are 12 m2 / g and 43 mg / g and for tannin-lignin-furfuryl gel – 72 m2 / g and 114.5 mg/g, respectively. It was found that an increase in the lignin content in the gel composition over 20 wt.% is accompanied by the phase localization of lignin (precipitation), which reduces the strength of the resulting gel and reduces its specific surface area.

scholarly journals A Facile Peroxo-Precursor Synthesis Method and Structure Evolution of Large Specific Surface Area Mesoporous BaSnO3

2015 ◽  
Vol 54 (8) ◽  
pp. 4002-4010 ◽  
Author(s):  
Chuande Huang ◽  
Xiaodong Wang ◽  
Quan Shi ◽  
Xin Liu ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Synthesis Method ◽  
Structure Evolution ◽  
Large Specific Surface Area ◽  
Precursor Synthesis

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.

Study of Heating Effect on Specific Surface Area, and Changing Optical Properties of ZnO Nanocrystals

2011 ◽  
Vol 403-408 ◽  
pp. 1205-1210
Author(s):  
Jaleh Babak ◽  
Ashrafi Ghazaleh ◽  
Gholami Nasim ◽  
Azizian Saeid ◽  
Golbedaghi Reza ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Energy Gap ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zno Nanocrystals ◽  
Transmission Electron ◽  
Zno Nanocrystal

In this work ZnO nanocrystal powders have been synthesized by using Zinc acetate dehydrate as a precursor and sol-gel method. Then the products have been annealed at temperature of 200-1050°C, for 2 hours. The powders were characterized using X-ray diffraction (XRD), UV-vis absorption and photoluminescence (PL) spectroscopy. The morphology of refrence ZnO nanoparticles have been studied using Transmission Electron Microscope (TEM). During the annealing process, increase in nanocrystal size, defects and energy gap quantitative, and decrease in specific surface area have been observed.

scholarly journals Ionothermally synthesized hierarchical porous Schiff-base-type polymeric networks with ultrahigh specific surface area for supercapacitors

RSC Advances ◽  
2017 ◽  
Vol 7 (32) ◽  
pp. 19934-19939 ◽  
Author(s):  
Yuhang Zhao ◽  
Ping Liu ◽  
Xiaodong Zhuang ◽  
Dongqing Wu ◽  
Fan Zhang ◽  
...  
Keyword(s):  
Schiff Base ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Synthesis Method ◽  
Ionothermal Synthesis ◽  
Polymeric Network ◽  
Polymeric Networks ◽  
Hierarchical Porous ◽  
One Step

A hierarchical porous polymeric network (HPPN) with ultrahigh specific surface area up to 2870 m2 g−1 was synthesized via a one-step ionothermal synthesis method without using templates.

Characterization of halloysite (North East Rif, Morocco): evaluation of its suitability for the ceramics industry

Clay Minerals ◽  
2018 ◽  
Vol 53 (1) ◽  
pp. 65-78 ◽  
Author(s):  
Abdelilah El Haddar ◽  
Elkhadir Gharibi ◽  
Ali Azdimousa ◽  
Nathalie Fagel ◽  
Iz-Eddine El Amrani El Hassani ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Fine Particles ◽  
High Plasticity ◽  
North East ◽  
Physico Chemical ◽  
Ceramics Industry ◽  
Tubular Crystals

ABSTRACTA halloysite clay from Nador (NE Morocco) was studied to evaluate its suitability in the ceramics industry. A cross-section involving all the Messinian facies was performed in the Melilla Neogene basin, at the foot of the Gourougou volcano, to establish the origin of the halloysite and estimate its reserves. White layers of halloysite and red clays rich in smectite occurring in contact with basal-reef limestone were characterized by mineralogical (XRD, IR), textural (SEM) and physico-chemical analyses (grain-size, Atterberg limits, DTA/TG, XRF and specific surface area). Ceramic properties were evaluated for halloysite fired from 500 to 1100°C to evaluate technical processing for ceramic production.The halloysite clay consists of fine particles with a high plasticity and a large specific surface area. The XRD investigation revealed the presence of 7 Å non-hydrated halloysite along with gibbsite, alunite, K-feldspar and traces of smectite and illite.The presence of halloysite was confirmed from the characteristic IR bands at 3695 and 3618 cm−1and the predominance of tubular crystals observed in the SEM. The chemical analysis revealed high contents linked to the presence of Al-rich phases (gibbsite and alunite). DTA/TG and XRD results of fired clay samples proved the dehydroxylation of halloysite and a rearrangement of metakaolinite to form mullite and spinel at 975°C.The Moroccan halloysite might be suitable for refractory ceramic applications. However, addition of quartz sand might be necessary to avoid crack development during firing and to reduce the plasticity of raw halloysite and minimize shrinkage during sintering.

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