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Mineral Acid (mineral + acid)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Multiple Functionalization of Mesoporous Silica in One-Pot: Direct Synthesis of Aluminum-Containing Plugged SBA-15 from Aqueous Nitrate Solutions,

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2008
Y. Wu
Abstract Aluminum-containing plugged mesoporous silica has been successfully prepared in an aqueous solution that contains triblock copolymer templates, nitrates, and silica sources but without using mineral acid. The acidity of the solution can be finely tuned from pH 1.4 to 2.8 according to the amount of the introduced aluminum species which ranged from an Al/Si molar ratio of 0.25/1 to 4.0/1. The aluminum nitrate additive in the starting mixture, along with the weak acidity produced by the nitrates, contributes to the formation of plugged hexagonal structures and the introduction of different amounts of aluminum species into the mesostructure. Characterization by X-ray diffraction, transmission electron microscopy, and N2 sorption measurements show that the Al-containing plugged silicas possess well-ordered hexagonal mesostructures with high surface areas (700,860 m2,g,1), large pore volume (0.77,1.05 cm3,g,1) and, more importantly, combined micropores and/or small mesopores in the cylindrical channels. Inductively coupled plasma,atomic emission spectrometry results show that 0.7,3.0 wt,% aluminum can be introduced into the final samples. 27Al MAS NMR results display that about 43,60% aluminum species are incorporated into the skeleton of the Al-containing silicas and the amount of the framework aluminum increases as the initial added nitrates rises. Scanning electron microscopy images reveal that the directly synthesized Al-containing plugged silica has a similar morphology to that of traditional SBA-15. Furthermore, the Al-containing plugged samples have excellent performances in the adsorption and the catalytic decomposition of isopropyl alcohol and nitrosamine. Finally, the direct synthesis method is used to produce plugged mesoporous silicas that contain other metals such as chromium and copper, and the resultant samples also show good catalytic activities. [source]

Degradation of polyamide-6 by using metal salts as catalyst,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10-12 2002
a Klun
Abstract Polyamide-6 (PA-6) is a widely used polycondensation polymer that can be recycled by hydrolysis to its monomer ,-caprolactam. The reaction is normally catalyzed by mineral acids. Using microwaves as the source of heating, zinc chloride, acetate and triflate were evaluated as non-acid catalysts for the reaction. Gravimetric and electron spray ionization mass spectrometry analysis of reaction products showed ZnCl2 as the most effective salt catalyst. A 50wt% (versus PA-6) addition gave 75% water-soluble, low-molecular-weight oligomers, which is approximately 25% lower than when using phosphoric acid. The triflate salt was effective only when used as an addition to a mineral acid, whereas the acetate was ineffective. FTIR and NMR spectroscopy of degradation products showed that dissociated ions from ZnCl2 bind to the amide group of the polymer. Using the triflate salt no such interaction could be observed, indicating that the degradation and catalysis mechanisms differ with the chloride and triflate salt. Five water-stable lanthanide triflates showed no catalytic effect on the reaction. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Direct Synthesis of Zr-Containing Hybrid Periodic Mesoporous Organosilicas with Tunable Zirconium Content

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2007
Shang-Ru Zhai
Abstract Highly ordered Zr-containing periodic mesoporous organosilicas (ZrPMO) with different Zr/Si ratios were successfully synthesized, for the first time, by employing a ZrOCl2/NaCl combination as the promoting agent and by simply adjusting the molar ratio of the zirconium species to the organosilica precursor; no addition of mineral acids was necessary. The effect of preparation parameters on the structural and textural properties were carefully investigated by using different ratios of NaCl/Si and Zr/Si. It was found that both salts are essential for this system and highly ordered ZrPMOs can be prepared within fairly wide Si/Zr ratios (5,100) while keeping the NaCl/Si ratio constant. To prove the effectiveness of this synthetic pathway with a higher Zr incorporation, ZrPMO materials were also synthesized under strongly acidic conditions for the purpose of comparison. The synthesized ZrPMO materials were thoroughly characterized by ICP-AES, SAXS, N2 sorption, TEM, SEM, 13C CP/29Si MAS NMR spectroscopy, XPS, and TGA. Elemental analyses show that the amount of Zr incorporated into ZrPMO, which was synthesized under mild conditions, is greater than that obtained in a strongly acidic environment, and the Zr content, with a Si/Zr ratio up to 12, is close to that in the initial gel composition. A plausible assembly mechanism based on the synergistic effect of both "nonhydrolyzable" (NaCl) and "hydrolyzable" (ZrOCl2) inorganic salts was discussed in detail, where the "salting out" effect and self-generated acidity from both inorganic salts, respectively, are believed to be key factors for the formation of ordered SBA-15-type ZrPMO materials under the synthetic conditions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]