Journal
CATALYSIS TODAY
Volume 147, Issue -, Pages S58-S65Publisher
ELSEVIER
DOI: 10.1016/j.cattod.2009.07.043
Keywords
Honeycomb monoliths; Rice husk; Carbonization; Textural properties; Silica leaching
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The possibility of preparing honeycomb monoliths from unconventional materials with high adsorption capacity, such as carbonized rice husk (CRH), was studied. Two schemes including modification of the porous structure by silica leaching were suggested for preparation of the monoliths: (1) preparation of CRH monoliths with the addition of Ca-montmorillonite (Ca-M) followed by leaching and (2) preliminary leaching of initial components followed by monolith extrusion. Chemical and textural properties of the materials were studied at each preparation step, The effect of temperature of rice husk (RH) pyrolysis and conditions of leaching treatment on the physico-chemical properties of CRH was investigated. By the data of nitrogen adsorption and SEM characterization, CRH has low specific surface area, pore volume less than 0.1 cm(3)/g, and composed mainly of macropore channels 5-10 mu m in diameter, micropores less than 17 angstrom in size, and a minor amount of mesopores. Treatment of the carbonized product with a 12% solution of potassium hydroxide at 80-100 degrees C leads to a 90-95% leaching of SiO2 from the CRH composite and increases the specific surface area to 400 m(2)/g and pore volume to 0.4 cm(3)/g due to formation of mesoporous structure. The feasibility of CRH honeycomb monoliths preparation and applicability of silica leaching from the monolith material for modification of the porous structure are demonstrated. The resulting monoliths are characterized by specific surface area exceeding 300 m(2)/g, pore volume 0.3 cm(3)/g, and high mechanical strength. (C) 2009 Elsevier B.V. All rights reserved.
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