Mesoporous carbon/silica nanocomposites with acid and base properties for glucose conversion into value added chemicals

Abstract

The purpose of this study is to prepare mesoporous carbon/silica (MCS) nanocomposites using natural rubber (NR) as a renewable carbon source. A series of mesoporous nanocomposites based on NR and hexagonal mesoporous silica (HMS), prepared via an in situ sol-gel process, were used as precursors, which were then converted into the MCS materials by carbonization. The sulfonic acid-functionalized mesoporous carbon/silica (MCS-SO3H) was prepared by direct sulfonation with H2SO4 solution. The silica surface of MCS-SO3H were then grafted by 3-aminopropyltrimethoxysilane to produce the acid–base catalysts (MCS-SO3H-NH2) and used as the solid catalysts in glucose conversion. The MCS nanocomposites exhibited enhanced structural, textural, and hydrophobic properties after increasing the carbonization temperature up to 700 ºC, while using a high concentration of H2SO4 solution promoted rubber conversion into carbon residues, resulting in an increased carbon content. Conversion of fructose to 5-hydroxymethylfurfural (HMF) increases with an increase in the acidity of the MCS-SO3H catalysts. MCS-SO3H-NH2 has prospect for the HMF synthesis from glucose. In addition, the formation of levulinic acid, as a byproduct from HMF hydrolysis, was retarded over the MCS-base nanocomposite catalysts. Moreover, the MCS-SO3H-NH2 catalysts exhibited reusability in the glucose dehydration for at least 3 cycles.