scholarly journals Characterization of Modified and Polymer Coated Alumina Surfaces by Infrared Spectroscopy

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Ashraf Yehia El-Naggar
Keyword(s):  
Infrared Spectroscopy ◽  
Alkali Metal ◽  
Ftir Spectroscopy ◽  
Surface Properties ◽  
Adsorption Properties ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Structure Changes ◽  
The Individual

The prepared, modified, and coated alumina surfaces were characterized by infrared spectroscopy (FTIR) to investigate the surface properties of the individual and double modified samples. FTIR helps in reporting the changes occurred in hydroxyl groups as well as the structure changes as a result of thermal treating, hydrothermal treating, silylation treating, alkali metal treating, coating, and bonding with polymer. FTIR spectroscopy represents the strength and abundance of surface acidic OH which determine the adsorption properties of polar and nonpolar sorbents. Generally, all treated samples exhibit decrease of OH groups compared with those of parent ones producing alumina surfaces of different adsorptive powers.

Active surface centres in vanadium pentoxide/alkali metal sulphate heterogeneous catalysts for 2-propanol decomposition

1979 ◽  
Vol 57 (18) ◽  
pp. 2464-2469 ◽  
Author(s):  
David Victor Fikis ◽  
William John Murphy ◽  
Robert Anderson Ross
Keyword(s):  
Alkali Metal ◽  
Surface Area ◽  
Vanadium Pentoxide ◽  
Heterogeneous Catalysts ◽  
Catalyst Activity ◽  
Active Surface ◽  
Hydroxyl Groups ◽  
Kinetic Measurements ◽  
The Stability ◽  
The Individual

Infrared spectra of the surfaces of vanadium pentoxide and vanadium pentoxide containing 9.09 mol% caesium and potassium, as sulphates, have been determined after exposure to 2-propanol for various times. Interpretation of the spectra leads to the proposal that the principal source of catalyst activity may be associated with surface hydrogen and hydroxyl groups on V5+ and V4+ sites. The "stability" of the catalysts towards reduction by the alcohol was consistent with the activity series derived from kinetic measurements: V2O5 (pure) < V2O5 (Cs) < V2O5 (K). The degree of sample reduction has also been assessed qualitatively by measurements of the ratio of surface area before to that after reaction and the same catalyst sequence was established. The trend in surface area ratios was similar to that shown by the surface "Tammann" temperatures of vanadium pentoxide and alkali metal sulphates which has been taken to imply that the ease and (or) extent with which the sulphates enter into inter-solid reactions with the oxide in the preparation stage may exert influence on the subsequent reducibility of the individual members of the catalyst series.

scholarly journals Water Adsorption Properties of Free and Dehydrated β-Cyclodextrin Studied by near Infrared Spectroscopy and Gravimetry

2016 ◽  
Vol 689 ◽  
pp. 143-147 ◽  
Author(s):  
Alfred A. Christy
Keyword(s):  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Water Adsorption ◽  
Near Infrared ◽  
Adsorption Properties ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Near Infrared Spectra ◽  
Adsorption Of Water

β-cyclodextrin, like other carbohydrates has a tendency to adsorb water molecules and the properties are attributed to the hydroxyl groups in the molecules. β-cyclodextrin, the cyclic oligomer of glucose has a hydrophobic interior and hydrophilic exterior. The cyclic structure favours the formation of hydrogen bonds between the OH groups on the adjacent glucose units and affects the formation of hydrogen bonds with water molecules. The hydoxyl groups engaged in hydrogen bondings can be eliminated at high temperatures and the adsorption properties of the dehydrated β-cyclodextrin will depend on the new functional groups formed. The aim of the report is to discuss the issue of the water adsorption properties of free and dehydrated β-cyclodextrin. Dry β-cyclodextrin and dehydrated β-cyclodextrin at temperatures 250, 300 and 350 °C were allowed to adsorb water from a humidity controlled air environmennt and the evolving near infrared spectra were measured using a near infrared spectrometer equipped with a transflectance accessory. The near infrared spectra in the region 10,000-4000 cm-1 and their second and fourth derivative profiles were used in studying the variation in the adsorption characteristics of dehydrated β-cyclodextrin. The results of the analyses show that the adsorption of water by β-cyclodextrin decreses at 300 °C compared to 200 and 250 °C. Dehydration forms more of the ethereal type-O-bonds in the molecule and explains the decrease in the water molecular adsorption at higher dehydration temperatures.

Comparison of Water Adsorption Properties of Cellulose and Cellulose Nanocrystals Studied by Near-Infrared Spectroscopy and Gravimetry

2017 ◽  
Vol 735 ◽  
pp. 235-239 ◽  
Author(s):  
Thamonwan Angkuratipakorn ◽  
Jirada Singkhonrat ◽  
Alfred A. Christy
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Cellulose Nanocrystals ◽  
Water Adsorption ◽  
Near Infrared ◽  
Adsorption Properties ◽  
Water Molecules ◽  
Oh Groups ◽  
Adsorption Processes ◽  
Adsorption Of Water

The adsorption properties of water molecules on cellulose and cellulose nanocrystals (CNCs), isolated from defatted rice bran (DRB) by 55% sulfuric acid hydrolysis under sonication were investigated. The powdered samples of cellulose and CNCs were analysed by using near infrared spectroscopy (NIR) and gravimetry at 38% and 55% humidities. Small amounts of samples were dried under vacuum at 120°C and the NIR spectra of the dry samples and their spectra during the adsorption water molecules were measured by using an NIR spectrometer equipped with a transflectance accessory and a DTGS detector. The quantitative adsorption of water molecules by the samples was determined by gravimetry. Second and fourth derivative profiles of the NIR spectra were used in understanding the chemistry of adsorption of water molecules and the adsorption processes by the samples. The results show that the adsorption of water molecules by the cellulose samples gives rise to three prominent peaks that can be related to the water molecules engaged in hydrogen bonding with C2, C3 and C6-OH groups on the glucose units of the cellulose polymers. Furthermore, the cellulose nanocrystals adsorb twice as much of water as the cellulose polymer. It is also clear from the results that C2 and C3-OH groups in the glucose units adsorb water molecules at a faster rate than the C6-OH group and responsible for nearly 50% of the water adsorption.

scholarly journals Chemical modification and characterization of boehmite particles

2008 ◽  
Vol 2 (1) ◽  
pp. 27-32
Author(s):  
Witold Brostow ◽  
◽  
Tea Datashvili ◽  
Keyword(s):  
Fourier Transform ◽  
Water Adsorption ◽  
Surface Characteristics ◽  
Surface Hydrophobicity ◽  
Hydroxyl Groups ◽  
Commercial Alumina ◽  
Inorganic Hybrid ◽  
Oh Groups ◽  
Powder Surface

Polymerizable organic silane molecules 3-(trimethoxysilyl)propylmethacrylate (3MPS) and vinyltri(2-methoxyethoxy)silane (VTMES) have been introduced onto surfaces of high purity Boehmite (a commercial alumina) via hydroxyl groups on the oxides in order to obtain organic-inorganic hybrid “macromonomers”. Changes of surface characteristics have been determined using thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). The influence of the type of silane used and modification conditions have been determined. Preheating was applied to some Boehmite samples; it leads to lower concentrations of –OH groups on the powder surface and the adsorption yields lower than in samples without preheating. Modification leads to surface hydrophobicity and thus reduces significantly water adsorption; in TGA we see desorption of water below 423 K only in un-modified Boehmite.

Preparation and infrared spectroscopic characterization of reduced-charge montmorillonite with various Li contents

Clay Minerals ◽  
1996 ◽  
Vol 31 (2) ◽  
pp. 233-241 ◽  
Author(s):  
J. Madejová ◽  
J. Bujdák ◽  
W. P. Gates ◽  
P. Komadel
Keyword(s):  
Infrared Spectroscopy ◽  
Spectroscopic Characterization ◽  
Layer Charge ◽  
Preparation Temperature ◽  
Oh Groups ◽  
Tetrahedral Sheet ◽  
Increasing Temperature ◽  
Octahedral Cations ◽  
Variable Layer

AbstractA series of reduced-charge montmorillonites (RCMs) was prepared from Li-montmorillonite from Jelšový Potok (Slovakia) by heating at various temperatures (105–210°C for 24 h. The amount of fixed Li, 0.09–0.67 per O20(OH)4, increased with increasing temperature, confirming preparation of a set of samples of variable layer charge from the same parent Li-montmorillonite by varying only the preparation temperature. Infrared spectroscopy revealed that Li was trapped in the hexagonal cavities of the tetrahedral sheet at all temperatures. Partial deprotonation of the samples, reflected in the decrease of the intensities of the OH-bending bands, was observed after treatments above 120°C. Analysis of the OH-stretching region showed Li in the previously vacant octahedra in the samples heated above 150°C. Weak inflections near 660 and 720 cm−1 confirmed development of local trioctahedral character of octahedral cations coordinated with OH groups in the sample heated at 210°C. Gradual decrease of the layer charge due to Li fixation led to a shift of the Si-O stretching band to higher frequencies and to the appearance of new, pyrophyllite-like bands at 1120 and 419 cm−1.

scholarly journals Solid-state 1H and 31P NMR and FTIR spectroscopy study of static and dynamic structures in sol-gel derived calcium hydroxyapatites

2015 ◽  
Vol 55 (1) ◽  
Author(s):  
Laurynas Dagys ◽  
Vytautas Klimavičius ◽  
Jonas Kausteklis ◽  
Ala Chodosovskaja ◽  
Valdemaras Aleksa ◽  
...  
Keyword(s):  
Ftir Spectroscopy ◽  
Sol Gel ◽  
Adsorbed Water ◽  
Calcium Hydroxyapatite ◽  
Hydroxyl Groups ◽  
Signal Shape ◽  
Distribution Profile ◽  
Oh Groups ◽  
Spin Lattice ◽  
Dynamic Structures

Calcium hydroxyapatite containing amorphous phosphate phase (ACP-CaHA) and nano-structured hydroxyapatite (CaHA) have been prepared by two sol-gel synthesis routes. The structural organization of hydroxyl groups in both materials has been determined by means of 1H MAS NMR and FTIR spectroscopy. It has been shown that the amount of structural –OH groups in nano-structured CaHA is significantly higher than that from adsorbed water and vice versa in ACP-CaHA. A precise signal shape analysis has been carried out for both studied samples. The 31P NMR signals have been found being Voigt-shaped in the wide-line as well as in MAS spectra. The 1H and 31P spin-lattice and spin-spin relaxation time measurements have revealed that the fast spin motion takes place in ACP-CaHA. The corresponding correlation time τ ~ 7 · 10–7 s at ~300 K has been determined. The effect of MAS rate on the 31P signal shape also confirms that this motion runs in the time scale of microseconds or even nanoseconds. The magnitude of the anisotropic broadening 1220 ± 20 Hz determined for nano-structured CaHA is very close to the maximum of the dipolar 1H–31P coupling distribution profile estimated using CP MAS kinetics. The dynamics of 1H–31P spin interactions in nano-structured CaHA (τ ~ 3.3 · 10–5 s) is much slower than in ACP-CaHA.

A study of hydroxyl groups in kaolin minerals utilizing selective deuteration and infrared spectroscopy

Clay Minerals ◽  
1967 ◽  
Vol 7 (1) ◽  
pp. 51-61 ◽  
Author(s):  
Koji Wada
Keyword(s):  
Infrared Spectroscopy ◽  
Interlayer Space ◽  
Hydroxyl Groups ◽  
Absorption Bands ◽  
Orientation Data ◽  
Oh Groups ◽  
Percentage Decrease ◽  
Inner Surface ◽  
Selective Deuteration

AbstractThe OH-OD exchange of kaolin minerals through contact with D2O introduced into interlayer space via intersalation resulted in a partial shift of the OH absorption bands. The total decrease in OH absorbance upon deuteralion was 52, 56, and 47% for the kaolinite, dickite-nacrite, and halloysite respectively, but the percentage decrease differed for the different absorption maxima of any one mineral. A secondary OH—OD exchange in the deuterated specimens was also observed upon heating to 350 and 400° C. These data together with the lack of deuteration in montmorillonite, and available orientation data on the kaolin OH groups by infrared spectroscopy, suggest that only two-thirds of the inner-surface OH groups form the interlayer OH—O bonds.

Infrared spectroscopy of ferrihydrite: evidence for the presence of structural hydroxyl groups

Clay Minerals ◽  
1979 ◽  
Vol 14 (2) ◽  
pp. 109-114 ◽  
Author(s):  
J. D. Russell
Keyword(s):  
Infrared Spectroscopy ◽  
Ir Spectroscopy ◽  
Room Temperature ◽  
Adsorbed Water ◽  
Deformation Vibration ◽  
Hydroxyl Groups ◽  
Absorption Bands ◽  
Oh Groups ◽  
Structural Hydroxyl

AbstractIR spectroscopy has shown that adsorbed water is almost completely removed from ferrihydrite by evacuation at room temperature. Absorption bands at 3615 and 3430 cm−1 appearing thereafter are interpreted as arising from OH groups located respectively at the surface and deeper in the structure. These groups are readily converted to OD on treatment with D2O vapour and this has allowed the OH deformation vibration to be identified at 800 cm−1. It is proposed that OH groups in ferrihydrite are about half as numerous as those in akaganéite (β-FeOOH) and that they may occur in environments similar to those in this mineral. The formula for ferrihydrite proposed by earlier workers, 5 Fe2O3.9H2O, should thus be amended to Fe2O3. 2 FeOOH.2·6H2O in order to indicate the presence of structural OH groups. A re-appraisal of the ferrihydrite structure appears desirable.

scholarly journals Characterization of Bioactive compound isolated from Myrothecium spp. with UV, FTIR and HPLC Analysis

2015 ◽  
Vol 3 (01) ◽  
pp. 01-05 ◽  
Author(s):  
Mohammad Rizwan Pervez1 ◽  
Mohammed Musaddiq ◽  
Prashant V. Thakare ◽  
Ashutosh Kumar
Keyword(s):  
Ftir Spectroscopy ◽  
High Performance ◽  
Process Development ◽  
Opportunistic Infections ◽  
Antibiotic Production ◽  
Bioactive Compound ◽  
New Drugs ◽  
Hydroxyl Groups ◽  
Chromatography Analysis

Development of new drugs, especially in area of infectious diseases, represents today one of the most important research. Fungal isolates are receiving increasing attention by natural product chemists due to their diverse and structurally unprecedented compounds making them interesting candidates for drug discovery. In fact, need for novel, safe and more efficient antibiotics is a key challenge to the pharmaceutical industry today, moreover, increase in opportunistic infections in the immune compromised host has influenced this demand. Nowadays, evaluating morphological and biochemical differences as well as studying fungal genetic diversity via molecular indicators seem to be the most common method for screening this genus. In this research we evaluate the potential of bioactive compound, production and characterize the UV and FTIR spectroscopy and HPLC (High performance liquid chromatography) analysis pattern of isolated Myrothecium spp. MRP001. Process development for high level production of bioactive compound was applied using OFAT method. Then, following the extraction of secondary metabolite, the UV and FTIR spectroscopy analysis was carried out for characterization of the various extracts. Considering the coordinate analysis of UV and FTIR spectroscopy pattern, the isolate MRP001 with substantial antimicrobial activity exhibited absorption at 3411 cm-1 which is indicator of hydroxyl groups, absorption at 2856 and 2915 cm-1 indicating hydrocarbon chassis, and absorption at 1649 cm-1 indicating a double bond of polygenic compound. These results highlight the importance of Myrothecium isolates in antibiotic production. HPLC confirmed the production when compared with standards

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