scholarly journals Peculiarities of Chemisorption of Dimethyl Carbonate on Silica Surface

2016 ◽  
Vol 17 (1) ◽  
pp. 88-92
Author(s):  
I.S. Protsak ◽  
E.M. Pakhlov ◽  
V.A. Tertykh
Keyword(s):  
Ir Spectroscopy ◽  
Fumed Silica ◽  
Dimethyl Carbonate ◽  
Silica Surface ◽  
Chemical Interaction ◽  
Spectroscopy Method ◽  
Silanol Groups

This paper presents the results of studies of dimethyl carbonate interaction with sites of the fumed silica surface. The investigations were performed in a vacuum quartz cuvette using IR spectroscopy method. Chemical interaction of dimethyl carbonate with sites of the dehydrated silica surface was shown to occur at temperature of 200 °C and higher, chemisorption processes take place involving both structural silanol groups and siloxane bridges on the surface.

scholarly journals Spectroscopic study on peculiarities of fumed silica hydridesilylation with triethoxysilane under fluidized bed conditions

2021 ◽  
Vol 12 (4) ◽  
pp. 314-325
Author(s):  
P. O. Kuzema ◽  
◽  
A. V. Korobeinyk ◽  
V. A. Tertykh ◽  
◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Surface Area ◽  
Fumed Silica ◽  
Silica Surface ◽  
High Surface ◽  
Space Filling ◽  
Silica Sample ◽  
Widespread Application ◽  
Silanol Groups ◽  
Heating Mode

Fumed silica has found widespread application in industry due to variety of fascinating properties. Owing to its specific manufacturing process, it consists of finely dispersed particles and is featured with large specific surface area covered by profoundly reactive silanol groups which are available for chemical grafting. Spherical shape of fumed silica particles and lacking porosity provides a space-filling structure. These characteristics implement the fume silica’s utilization as high-surface-area carriers for various catalysts, i.e. metallic nanometer-sized particles, organic moieties, etc. Currently a great attention is called to on-surface grafting to improve the silica-based carrier. Most of research is carried out in area of liquid phase chemistry involving an abundance of expensive and often toxic solvents while the space-filling properties of silica are favoring reactions in fluidized bed conditions. In current research fumed silica (A-300) was a subject for hydridesilylation with triethoxysilane under fluidized bed conditions. In all synthesis reported in current research the insignificant amount of solvent (1.00 wt. % of the amount used in typical wet-chemical modifications method) was spent for the silica surface silylation. While the mass ratio of silica/TES was kept constant, other conditions, i.e. solvent/catalyst presence, surface pretreatment, additional treatment with water, and the fluidized bed heating mode have been varied. FTIR spectroscopy revealed the interaction between groups of triethoxysilane and silica surface silanol groups and demonstrated the effect of modification conditions on the density of the hydridesilyl groups coverage. The results of FTIR spectroscopic studies have confirmed the presence of grafted silicon hydride groups on the surface of modified silica, as well as the presence of ethoxy and/or silanol groups – either intact or formed due to hydrolysis of the ethoxy groups. Titrimetric and spectrophotometric analysis was performed to estimate the concentration of grafted SiH groups (in all samples prepared under fluidized bed conditions their concentration ranged within about 0.28–0.55 mmol/g as dependent on the reaction conditions). Other important aspects of fluidization such as the presence of solvent and/or hydrolyzing agent, bed heating mode and the effect of the silica sample thermal pre-treatment are also discussed.

scholarly journals Study of Biologically Active Solid-phase Systems Based on Halogen-substituted Nitrobenzofuroxans by the IR Spectroscopy Method

2020 ◽  
Vol 9 (4) ◽  
pp. 32-39
Author(s):  
A. N. Khuziakhmetova ◽  
E. G. Gorelova ◽  
L. M. Yusupova ◽  
A. A. Kurmaeva
Keyword(s):  
Ir Spectroscopy ◽  
Intermolecular Interaction ◽  
Solid Phase ◽  
Chemical Interaction ◽  
Intermolecular Hydrogen Bond ◽  
Biologically Active ◽  
Spectroscopy Method ◽  
Phase System ◽  
Synergistic Activity ◽  
Phase Systems

Introduction. Biologically active compounds 4,6-dinitro-5,7-dichlorobenzofuroxan (4,6-DNDHBFO) and 5-nitro-4,6-dichlorobenzofuroxan (5-NDHBFO) effectively in-hibit ultra-resistant microorganisms: Staphylococcus aureus, pathogenic fungi – Aspergillius niger, Coniophora cerebella, Candida albicanas and other microor-ganisms. Mixed systems based on 4,6-DNDHBFO and 5-NDHBFO exhibit high potentiated synergistic activity against Aspergillius niger. Currently, there are no full-fledged studies about the mechanism of synergism of 5-NDHBFO and 4,6-DNDHBFO in a solidphase system. The results of the study of solid-phase sys-tems 5-NDHBFO – 4,6-DNDHBFO by IR spectroscopy will make it possible to establish the nature of the interaction between the components of the binary mix-ture.Aim. Experimental study of the intermolecular interaction of 5-NDHBFO with 4,6-DNDHBFO by the IR spectroscopy method.Materials and methods. The intermolecular interaction of 5-NDHBFO with 4,6-DNDHBFO at different ratios in a solid-phase system was studied by the IR spectroscopy method.Results and discussion. Based on the results of the study, the physico-chemical interaction of 5-NDHBPO with 4,6-DNDHBFO in solid-phase systems was revealed. Shifts and changes in the intensities of the characteristic frequencies of functional groups involved in the formation of intermolecular bonds between 5-NDHBPO and 4,6-DNDHBPO were revealed.Conclusion. The nature of the interaction between 4,6-DNDHBFO and 5-NDHBFO in the solid-phase system was established, leading to the appearance of a synergy effect. The interaction of 5-NDHBFO with 4,6-DNDHBFO in a bi-nary system is due to the formation of an intermolecular hydrogen bond. The in-teraction involves the proton of the 5-NDHBFO molecule, the oxygen of the fu-roxan ring of 4,6-DNDHBFO, as well as the halogen atom of 4,6-DNDHBFO at an equimolar ratio of the components of the solid-phase system.

scholarly journals The Morphology and Conductive Properties of Composite Material SiO2 – C

2015 ◽  
Vol 16 (4) ◽  
pp. 700-705
Author(s):  
I.F. Myronyuk ◽  
V.I. Mandzyuk ◽  
V.M. Sachko ◽  
Yu.O. Kyluk
Keyword(s):  
Composite Material ◽  
Fumed Silica ◽  
Silica Surface ◽  
Weight Ratio ◽  
Nitrogen Adsorption ◽  
Carbon Phase ◽  
Fumed Silica Nanoparticles ◽  
Structure Morphology ◽  
Open Porous Structure ◽  
Conductive Properties

The article explores the structure, morphology and conductive properties of composite material SiO2 – C using XRD, SAXS, low-temperature nitrogen adsorption, and impedance spectroscopy methods. It is set that SiO2 – C composite obtained by thermolytic decomposition of D-lactose, previously chemisorbed on fumed silica nanoparticles surface, has an open porous structure, in which mesopores of 6-12 nm in size are dominate. At weight ratio SiO2/C = 5/1 nanocrystallites of carbon phase in form of lamellar sheets of 0,4 × 0,4 × 5,0 nm3 in size contact with entire silica surface that results in composite material conductivity is 49 Оhm-1·m-1.

Modelling the surface of amorphous dehydroxylated silica: the influence of the potential on the nature and density of defects

2018 ◽  
Vol 42 (2) ◽  
pp. 1356-1367 ◽  
Author(s):  
Stéphanie Halbert ◽  
Simona Ispas ◽  
Christophe Raynaud ◽  
Odile Eisenstein
Keyword(s):  
Molecular Dynamics ◽  
Silica Surface ◽  
Silanol Groups

The nature and density of defects on the amorphous dehydroxylated silica surface are studied by molecular dynamics for information on the silanol groups of pretreated silica.

Ion speciation of lithium hexafluorophosphate in dimethyl carbonate solutions: an infrared spectroscopy study

2018 ◽  
Vol 20 (35) ◽  
pp. 22710-22718 ◽  
Author(s):  
Kristen D. Fulfer ◽  
Daniel G. Kuroda
Keyword(s):  
Infrared Spectroscopy ◽  
Ir Spectroscopy ◽  
Dimethyl Carbonate ◽  
Spectroscopy Study ◽  
Dft Computations ◽  
Carbonate Solutions ◽  
Lithium Hexafluorophosphate

The speciation of lithium hexafluorophosphate (LiPF6) in dimethyl carbonate as function of the concentration is studied via IR spectroscopy and DFT computations.

scholarly journals Clean chlorination of silica surfaces by a single-site substitution approach

2018 ◽  
Vol 47 (12) ◽  
pp. 4301-4306 ◽  
Author(s):  
Niladri Maity ◽  
Samir Barman ◽  
Edy Abou-Hamad ◽  
Valerio D'Elia ◽  
Jean-Marie Basset
Keyword(s):  
Silica Surface ◽  
Single Site ◽  
Silanol Groups ◽  
Silica Surfaces ◽  
Selective Chlorination ◽  
Hydrogen Bonded

Unveiling a clean, selective chlorination method for the quantitative substitution of well-defined non-hydrogen bonded silanol groups of the silica surface.

Interaction of trimethylchlorosilane with silanol groups silica surface in the presence of amines

1993 ◽  
Vol 50 (1-2) ◽  
pp. 305-310
Author(s):  
E. M. Pakhlov ◽  
V. M. Gun'ko ◽  
E. F. Voronin
Keyword(s):  
Silica Surface ◽  
Silanol Groups

The Influence of Fumed Silica Properties on the Processing, Curing, and Reinforcement Properties of Silicone Rubber

1993 ◽  
Vol 66 (1) ◽  
pp. 48-60 ◽  
Author(s):  
H. Cochrane ◽  
C. S. Lin
Keyword(s):  
Surface Area ◽  
Silicone Rubber ◽  
Fumed Silica ◽  
Silica Surface ◽  
Silica Network ◽  
Surface Pretreatment ◽  
Structure Level ◽  
Network Strength ◽  
Reinforcement Model ◽  
Mixing Techniques

Abstract The present study uses a commercial heat cured silicone rubber formula (including a process aid) and mixing techniques to investigate the effect of varying fumed silica properties—including load, surface area, silica structure level, and surface pretreatment levels—on the rubber processing, curing, and cured physical properties. Based on the results, a simple silica network reinforcement model was developed to explain the changes in processing, curing, and vulcanizate properties of the silicone elastomers. The network is held together by silica-silica interactions and silica-polymer-silica bridge bonds between the silica aggregates. Increasing the silica loading, surface area, and structure level increases the number of interactions and hence the network strength. The pretreatment of the silica surface with organosilane molecules reduces the strength of silica-silica and silica-polymer interactions, therefore, weakening the silica network. Furthermore, the good interrelations between the initial plasticity, crepe hardening, curing, modulus yield, and durometer values strongly supports the concept of the presence of a silica network within the compounds under the low strain conditions of the tests.

scholarly journals Labeling and Probing the Silica Surface Using Mechanochemistry and 17O NMR Spectroscopy

2021 ◽  
Author(s):  
Chia-Hsin Chen ◽  
Frederic Mentink-Vigier ◽  
Julien Trébosc ◽  
Ieva Goldberga ◽  
Philippe Gaveau ◽  
...  
Keyword(s):  
Fumed Silica ◽  
Silica Surface ◽  
17O Nmr ◽  
Surface Information ◽  
Clear Identification ◽  
Common Interface ◽  
Cost Efficient ◽  
User Friendly ◽  
First Time ◽  
17O Nmr Spectroscopy

In recent years, there has been increasing interest in developing cost-efficient, fast, and user-friendly <sup>17</sup>O enrichment protocols to help understand the structure and reactivity of materials using <sup>17</sup>O NMR. Here, we show for the first time how ball milling (BM) can be used to selectively and efficiently enrich the surface of fumed silica, which is widely used at the industrial scale. Short milling times (up to 15 min) allowed modulation of the enrichment level (up to ca. 5%) without significantly changing the nature of the material. High-precision <sup>17</sup>O-compositions were measured at different milling times using LG-SIMS. High-resolution <sup>17</sup>O NMR analyses (including at 35.2 T) allowed clear identification of the signals from siloxane (Si-O-Si) and silanols (Si-OH), while DNP analyses, performed using direct <sup>17</sup>O polarization and indirect <sup>17</sup>O{<sup>1</sup>H} CP excitation, agreed with selective<sup> </sup>labeling of the surface. Information on the distribution of Si-OH environments at the surface was obtained from 2D <sup>1</sup>H-<sup>17</sup>O D-HMQC correlations. Finally, the surface-labeled silica was reacted with titania and using <sup>17</sup>O DNP, their common interface was probed and Si-O-Ti bonds identified.

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