Adsorption of Benzene, Toluene, and p-Xylene on Microporous SiO₂

Abstract

Adsorption isotherms of aromatic BTX (benzene, toluene, and p-xylene) hydrocarbons on pure and Ag-doped SiO 2 microporous substrates synthesized by the sol-gel procedure have been measured by the gas chromatographic technique at several temperatures in the range between 423 and 573 K. Both Langmuir and Dubinin adsorption models can reasonably fit every set of BTX adsorption data at all temperatures. The uptake degree of these hydrocarbon adsorptives on both SiO 2 and Ag/SiO 2 microporous substrates is temperature-dependent. Additionally, the degrees of interaction of BTX molecules with SiO 2 and Ag/SiO 2 microporous walls have been investigated by evaluation of the corresponding isosteric heats of adsorption (q st ) by means of a Clausius-Clapeyron-type equation. The isosteric heats of adsorption of BTX hydrocarbons at different adsorbate loadings have been inferred from the adsorption isotherms and found to follow the decreasing sequence q st (benzene) < q st (toluene) < q st (p-xylene). Isosteric heats of adsorption of BTX compounds on SiO 2 microporous substrates have been found, in general, to increase with an increase in the adsorbate loading as a consequence of the cohesive interactions between adsorbate molecules. Addition of Ag atoms to the SiO 2 structure helps to homogenize the magnitudes of the isosteric heats of adsorption of the BTX compounds.

Shape dependence of nanoceria on complete catalytic oxidation of o-xylene

“…To date, many techniques have been developed to remove BTX from polluted air, such as adsorption, thermal oxidation, photocatalytic oxidation and catalytic oxidation, among which catalytic oxidation is one of the most environmentally friendly techniques due to its easy application, high efficiency and low cost. [4][5][6][7][8] Over the past few decades, complete catalytic oxidation of BTX has been widely studied over either supported noble metal or metal oxide catalysts. [9][10][11][12][13][14][15][16][17][18][19][20] Generally, noble metal catalysts exhibit higher activity than other metal oxide catalysts, and the former are more expensive than the latter.…”

Chlorobenzene, chloroform, and carbon tetrachloride adsorption on undoped and metal-doped sol–gel substrates (SiO2, Ag/SiO2, Cu/SiO2 and Fe/SiO2)

“…Raman et al [11] have studied the porosity of silica solids. Hernández et al [12,13] have pursued studies on the adsorption of hydrocarbons on microporous SiO 2 . Meixner et al [14] have investigated the adsorption of carbon tetrachloride, trimethylbenzene and perfluorotributylamine on microporous SiO 2 .…”

NEW METHOD OF OBTAINING GELATINE-SiO₂ COMPOSITE SYSTEMS USING 3-GLYCIDOXYPROPYLTRIMETHOXYSILANE AND 3-CHLOROPROPYLTRIMETHOXYSILANE

“…SiO 2 particles owe their great popularity from their optical, electrical or thermal properties. This is due to the possibility of regulating the porosity at the preparation stage, allowing the production of materials with a large amount of the active sites or high specific surface area or pore volume [12].…”