کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9617649 | 49176 | 2005 | 12 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Sol-gel synthesis of mesostructured γ-alumina templated by cationic surfactants
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
کاتالیزور
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چکیده انگلیسی
Sol-gel mesostructured γ-Al2O3 (SGAL) with pore walls largely formed by γ-Al2O3 nanocrystals has been synthesized by a new three step (hydrolysis, condensation and calcination) sol-gel procedure in acid medium with cationic surfactants (hexadecyltrimethylammonium chloride/bromide) and in the absence of hydrolysis retarding agents. SGAL aluminas showed BET surface areas larger than 300 m2 gâ1, pore diameters within the 4-15 nm range and pore volumes larger than 0.40 cm3 gâ1. Hydrogen chloride, water and surfactant contents as well as the thermal treatment deeply influence the final properties of the obtained aluminas. Hydrogen chloride/aluminium isopropoxide molar ratios larger than 1 are required to prepare uniform mesostructured aluminas of wormhole-like appearance with a narrow mesopore size distribution (Dp â¼Â 4.7-6.0 nm). A pore size decrease, accompanied by narrower mesopore size distributions has been observed when diminishing both the water/aluminium isopropoxide and template/aluminium isopropoxide molar ratios. Controlled two step thermal treatment (firstly heating under flowing nitrogen and subsequently under air flow at 550 °C for 5 h) allows to reduce the coalescence of the aluminium moieties forming the pore walls, by increasing the BET surface area values above 500 m2 gâ1. Under special conditions, ordered mesostructured alumina with SBET â¼Â 626 m2 gâ1, Dp â¼Â 2.8 nm and narrower pore walls (â¼3.5 nm) largely formed by γ-Al2O3 nanocrystals was prepared.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Microporous and Mesoporous Materials - Volume 83, Issues 1â3, 1 September 2005, Pages 181-192
Journal: Microporous and Mesoporous Materials - Volume 83, Issues 1â3, 1 September 2005, Pages 181-192
نویسندگان
J. Aguado, J.M. Escola, M.C. Castro, B. Paredes,