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Query: EC:4.1.2.42 (DTA)
 1,693 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Structural studies of hydroxy-aluminum phosphates with antacid application are performed. The antacid properties of the products depend on their chemical composition and way of preparation. Scanning electron microscope, X-ray- and IR-spectroscopy have evidenced the formation of a one-phase product. The IR-spectra indicate an Al-PO4 containing compound with an Al-PO4 bond. The high-temp. exothermic effect at 730-780 degrees C exhibited by the DTA curves of the hydroxy aluminum phosphates studies are due to polymorphic conversions which are not found with the sample having the best antacid properties. On the basis of these results it is not easy to prove that the higher acid-binding ability of this sample is due to the more favourable position of its acid-binding groups and the absence of phases undergoing polymorphic transformations at high temp. Probably the low pH value of precipitation favours the acid-binding ability. Toxicologic investigations on aluminum ion absorption in blood plasma have shown an admissible aluminium level.
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PMID:Studies of hydroxy-aluminum phosphates obtained from pentahydroxy-dialuminum chloride and monosodium phosphate. 227 10

Three kinds of amorphous aluminosilicates were synthesized by coprecipitation of silicic acid with aluminum hydroxide in the presence of different inorganic ions: sulfate, chloride, and nitrate. Although the bulk composition of the aluminosilicates obtained was not affected by anion species, their DTA spectra were significantly different, suggesting that their structures also differ. The local structure of Al and Si in the aluminosilicates was studied in detail by 27Al and 29Si MAS NMR. From the 27Al MAS NMR spectra and comparison between 29Si HD- and CP-MAS NMR spectra, it was concluded that the aluminosilicate obtained in the presence of sulfate ions has only a montmorillonite-like structure, whereas in the cases of chloride and nitrate, the solids are composed of three phases: aluminum hydroxide, silica, and the montmorillonite-like aluminosilicate. The difference in the local structure of Al and Si in the aluminosilicates was explained by the difference in interaction between the anions and aluminum ions. Copyright 1999 Academic Press.
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PMID:Effects of Anions on Local Structure of Al and Si in Aluminosilicates. 1033 80

Arsenic adsorption was carried out on simple materials such as goethite and amorphous iron hydroxide, and more complex matrices such as clay pillared with titanium(IV), iron(III), and aluminum(III). These matrices were synthesized from a bentonite whose montmorillonitic fraction was pillared according to optimized parameters. These sorbents were characterized by various methods: XRD, FTIR, BET, DTA/TGA, surface acidity, and zetametry. Elimination of arsenite and arsenate as a function of pH was studied. Arsenate elimination was favored at acidic pH, whereas optimal arsenite elimination was obtained at 4<pH<9. For pH values above 10, the pillared clays were damaged and elimination decreased. Equilibrium time and adsorption isotherms were also determined for arsenite and arsenate at each matrix auto-equilibrium pH. Amorphous iron hydroxide had the highest adsorption capacities both towards arsenate and arsenite. Adsorption capacities of goethite and iron- and titanium-pillared clays toward arsenate were similar, but those toward arsenite were different. Desorption experiments from the various matrices were carried out. Iron- and titanium-pillared clays showed a desorption capacity above 95% and around 40% respectively, but no desorption rate could be obtained for iron (hydr)oxides as they were damaged during the process.
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PMID:Arsenic adsorption onto pillared clays and iron oxides. 1270 67

The structure of the very strong solid Lewis acid aluminum chlorofluoride (ACF, AlCl(x)F(3-x), x = 0.05-0.3) was studied by IR, ESR, Cl K XANES, (19)F MAS NMR, and (27)Al SATRAS NMR spectroscopic methods and compared with amorphous aluminum fluoride conventionally prepared by dehydration of alpha-AlF(3) x 3H(2)O. The thermal behavior of both compounds was investigated by DTA and XRD. In comparison to ACF, amorphous AlF(3) prepared in a conventional way is not catalytically active for the isomerization reaction of 1,2-dibromohexafluoropropane, which requires a very strong Lewis acid. Both compounds are mainly built up of corner-sharing AlF(6) octahedra forming a random network. The degree of disorder in ACF is higher than in amorphous AlF(3). Terminal fluorine atoms were detected in ACF by (19)F NMR. The chlorine in ACF does not exist as a separate, crystalline AlCl(3) phase. Additionally, chlorine-containing radicals, remaining from the synthesis, are trapped in cavities of ACF. These radicals are stable at room temperature but do not take part in the catalytic reaction.
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PMID:Structural insights into aluminum chlorofluoride (ACF). 1451 24

Mercuric-5-nitrotetrazole (MNT) was synthesized on using a reported method. The product having bulk density of 1.5 g/cm3, was obtained during this work using mercuric nitrate doped with additives such as cephol/dextrin in the process. Synthesized MNT was characterized by metal content analysis, IR and ESCA. The DTA profile indicated the thermal stability of MNT up to 200 degrees C. It revealed its higher thermally sensitive [thermal sensitive figure (S) approximately 0.8] in comparison to that of service lead azide (SLA) [S approximately 0.4]. Percussion sensitivity data also showed higher sensitivity of MNT. However, it was found less friction sensitive than SLA. The chemical stability of MNT in a carbon dioxide environment was evaluated in comparison to SLA by determining mercury (gravimetrically) and lead azide (volumetrically) contents respectively. Results obtained indicated that no discernable changes occurred in MNT, even after storage for 90 days while in case of SLA, drastic change in lead azide content was observed. IR spectra of MNT sample stored in a closed aluminum dish for 5-10 years could be superimposed on that of the freshly prepared MNT sample. The performance of MNT filled detonator no. 27 assessed in terms of extent of damage on a witness plate was found equivalent to that of the standard ASA (azide, styphynate and aluminium) composition filled detonator.
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PMID:Synthesis, characterization, thermolysis and performance evaluation of mercuric-5-nitrotetrazole (MNT). 1536 11

The present study reports a green synthesis method for preparing pure (free of fly ash) and ordered MCM-41 materials from coal fly ash at room temperature (25 degrees C) during 24 h of reaction. It was shown that the impurities in the coal fly ash were not detrimental to the formation of MCM-41 at the tested conditions. The influence of initial synthesis pH on material properties of calcined MCM-41 samples was investigated by various techniques such as XRF, XPS, XRD, FTIR, DR-UV-vis, solid state NMR, N2 physisorption, TG-DTA, SEM and TEM. The experimental results showed that the amount of trace elements such as Al, Na, Ti and Fe incorporated into the sample increased with synthesis pH value. More aluminum species were incorporated with tetrahedral coordination in the framework under a high pH value. The particle size of the sample decreased with the synthesis pH value. Samples synthesized at high pH values had a larger pore size and were more hydrothermally stable than those at low pH values. From thermal analysis, it was observed that the synthesized MCM-41 samples showed a high thermal stability. These properties made the synthesized MCM-41 suitable for further processing into more useful materials in a wide range of applications.
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PMID:Synthesis of MCM-41 from coal fly ash by a green approach: influence of synthesis pH. 1664 13

A new light emitting material, salicylaldehyde anil zinc (SAZ), was synthesized. It can form high quality nano-scale amorphous thin films on clean glass substrates by vacuum evaporation. Its structure, crystallization, thermal stability, and optical property were investigated by IR spectra, DTA-TG analysis, XRD spectra, UV-Vis spectra, and fluorescence spectra. Its energy band structure was confirmed by cyclic voltammogram and optical absorption band edge. Results show that the SAZ film is a thermally stable material, and can emit intense green fluorescence with a peak wavelength at 508 nm and a full width at half-maximum of 90.2 nm under UV irradiation. Its HOMO energy level is about -5.659 eV, LUMO energy level is about -3.054 eV, optical gap band is about 2.604 eV. The fluorescence decay of stored films under ambient atmosphere is more rapid than that of 8-hydroxyquinoline aluminum films. However, the fluorescence decay of the films under UV irradiation is slower than that of 8-hydroxyquinoline aluminum films.
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PMID:[Spectroscopic properties of salicylaldehyde anil zinc and its thin film]. 1683 Jul 63

Amorphous mesoporous aluminophosphates (AlPO) with P/Al molar ratio in the range 0.8-1.15 are synthesized by using the citric acid (CA) route and are systematically characterized using N(2)-adsorption, XRD, SEM, solid-state CP-MAS NMR, FT-IR, TG-DTA, CO(2)-TPD, and NH(3)-TPD. The characterization studies show that the change in P/Al ratio could affect the structure, texture, thermal stability, and surface acid-base properties of AlPO. Samples with a relatively low P/Al ratio (< or =1.0) exhibit uniform amorphous mesoporous character and high thermal stability (up to 1173 K). Partial crystallization of the AlPO framework easily occurred on the sample with higher P/Al ratio (> or =1.1), thus leading to significant decrease of surface area and formation of particle pile mesopores. Both weak acid and weak base sites are observed over AlPO materials, and the amounts of acid-base sites can be effectively controlled by adjusting the P/Al ratio. The presence of suitable interaction between citric acid and AlPO framework is critical for the formation of mesoporous structures. Both CA and PO(4) units are considered to be ligands to coordinate with aluminum ions, forming relative uniform complexes (such as CA-Al-PO(4)) in the as-synthesized AlPO materials. The mesoporous structure of AlPO materials is obtained after the rapid decomposition of citric acid. Vapor phase selective O-methylation of catechol with methanol reaction is carried out to investigate the catalytic performances of AlPO materials with different P/Al ratios. Among them, AlP(1.1)O shows the highest activity (88.4% conversion of catechol) and the highest yield of guaiacol (74.3%). The presence of suitable weak acid-base pairs may play an important role on the title reaction.
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PMID:Thermally stable amorphous mesoporous aluminophosphates with controllable P/Al ratio: synthesis, characterization, and catalytic performance for selective O-methylation of catechol. 1692 87

Alumina is the most frequently employed catalyst or catalytic support in the chemical industry. The catalytic performances of alumina-supported catalysts are largely dependent on the textural properties of the alumina supports. Therefore, any improvement of the alumina properties significant for their catalytic applications is extremely challenging. Ordered mesoporous aluminas with high thermal stability have been successfully prepared by a facile synthesis method. Using the ordered mesoporous aluminas as support, V/Ni-catalysts mesoporous materials also have been prepared by vacuum impregnation method and the coprecipitation method. The mesoporous structures are characterized by XRD, TEM, N2 adsorption -desorption and TG-DTA. Preliminary catalytic tests showed that the ordered mesoporous aluminas prepared in such a way exhibited superior performance in the oxidative dehydrogenation of propane to propylene when they were used as the supports for V and Ni catalysts.
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PMID:Synthesis, characterization and catalytic applications in propane dehydrogenation of ordered mesoporous alumina. 1990 92

For the first time, high surface area nanofibers were synthesized using aluminum isopropoxide monomer with acetic acid as the polycondensation agent in the green solvent, supercritical carbon dioxide (scCO(2)). It was found that the synthesis temperature, pressure, concentration, and acid/alkoxide ratio had a large effect on fiber formation. By optimizing the experimental conditions at 80 degrees C and 6000 psi of scCO(2) using aluminum isopropoxide at a concentration of 0.3 mmol/mL and acid/alkoxide ratio of 10, alumina nanofibers were formed ranging from 11 to 22 nm in diameter and 500 to 1000 nm in length, and with surface areas up to 580 m(2)/g. Lower temperatures gave irregular shaped nanoparticles, while a lower acid/alkoxide ratio (5:1) resulted in the formation of low surface area alumina bars. Increasing pressure led to better separation of the nanofibers and higher surface areas. In addition to the synthesis conditions, the influence of calcination temperature on the structural, textural, and morphological properties of the materials was examined using various physicochemical techniques including electron microscopy, TGA/DTA, powder XRD, FTIR, XPS, and nitrogen adsorption/desorption analysis. The long fibers with high aspect ratios were found to be thermally stable even after calcining at up to 1050 degrees C. The mechanism of fiber formation in scCO(2) is proposed based on a [Al(OH)(CH(3)CO(2))(2)](n) polycondensate backbone.
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PMID:One-pot procedure to synthesize high surface area alumina nanofibers using supercritical carbon dioxide. 2014 Dec 11


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