TY - JOUR

T1 - The impact of Si/Al ratio on properties of aluminosilicate aerogels

AU - Shalygin, Anton S.

AU - Kozhevnikov, Ivan V.

AU - Gerasimov, Evgeny Yu

AU - Andreev, Andrey S.

AU - Lapina, Olga B.

AU - Martyanov, Oleg N.

PY - 2017/10

Y1 - 2017/10

N2 - The Si/Al ratio is a key parameter of acid-base, structural, textural and, consequently, catalytic properties of amorphous crystalline (micro- and mesoporous) aluminosilicates. The changes of structural and textural characteristics of Al-Si aerogels with gradual increase of aluminum content are investigated. Aerogels were prepared via sol-gel method using prehydrolysed tetraethoxysilane and aluminium isopropoxide stabilized by acetylacetone. The gelation of the obtained sols took place in the presence of ammonia with the following drying in supercritical isopropanol. It was shown all aluminum reacts with prehydrolyzed tetraethoxysilane forming spherical particles in case the content of Al in the samples is less than 20 mol %. Aluminum drives the increase of interparticle coupling leading to the particle agglomeration, which is associated with the increase of the particle size and decrease of specific surface area and pore volume. For the samples with the aluminum content of >50 mol % the formation of pseudoboehmite plate-like particles is observed. The pseudoboehmite particles prevent the sintering of SiO2 particles that leads to the increase of the aerogel specific surface area and pore volume. In case the high aluminum content (>80 mol %) the silica particles serve as a connector between boehmite plates. The ratio between Brønsted and Lewis acid sites decreases gradually with the increase of aluminum content of the aluminosilicate aerogels.

AB - The Si/Al ratio is a key parameter of acid-base, structural, textural and, consequently, catalytic properties of amorphous crystalline (micro- and mesoporous) aluminosilicates. The changes of structural and textural characteristics of Al-Si aerogels with gradual increase of aluminum content are investigated. Aerogels were prepared via sol-gel method using prehydrolysed tetraethoxysilane and aluminium isopropoxide stabilized by acetylacetone. The gelation of the obtained sols took place in the presence of ammonia with the following drying in supercritical isopropanol. It was shown all aluminum reacts with prehydrolyzed tetraethoxysilane forming spherical particles in case the content of Al in the samples is less than 20 mol %. Aluminum drives the increase of interparticle coupling leading to the particle agglomeration, which is associated with the increase of the particle size and decrease of specific surface area and pore volume. For the samples with the aluminum content of >50 mol % the formation of pseudoboehmite plate-like particles is observed. The pseudoboehmite particles prevent the sintering of SiO2 particles that leads to the increase of the aerogel specific surface area and pore volume. In case the high aluminum content (>80 mol %) the silica particles serve as a connector between boehmite plates. The ratio between Brønsted and Lewis acid sites decreases gradually with the increase of aluminum content of the aluminosilicate aerogels.

KW - Aerogels

KW - Aluminosilicate

KW - Si/Al ratio

KW - Sol-gel method

KW - Supercritical drying

KW - POROSITY

KW - SOL-GEL METHOD

KW - SILICA-ALUMINA

KW - SURFACE-AREA

KW - MULLITE

KW - NMR

KW - XEROGELS

KW - SITES

KW - CATALYSTS

KW - ACIDITY

UR - http://www.scopus.com/inward/record.url?scp=85020312949&partnerID=8YFLogxK

U2 - 10.1016/j.micromeso.2017.05.053

DO - 10.1016/j.micromeso.2017.05.053

M3 - Article

AN - SCOPUS:85020312949

VL - 251

SP - 105

EP - 113

JO - Microporous and Mesoporous Materials

JF - Microporous and Mesoporous Materials

SN - 1387-1811

ER -