New silica/alumina–clay heterostructures: Properties as acid catalysts

• Published in: Microporous and mesoporous materials Vol. 147; no. 1; pp. 157 - 166
• Main Authors: Belver, C., Aranda, P., Martín-Luengo, M.A., Ruiz-Hitzky, E.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 2012; Elsevier
• Subjects: Acid catalysts; Catalysis; Chemistry; Clay-based heterostructures; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Montmorillonite; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Porous materials; Silica/alumina; Sol–gel; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Clay-based heterostructures; Montmorillonite; Sol–gel; Acid catalysts; Silica/alumina; Modification; Binary compound; Inclusion; Nanoparticle; Silicates; Porous material; Silica; Solid; Sol―gel; Synthesis; Cymene; Alkoxide; Pillared clay; Clay; 1,8-p-Menthadiene; Composition; Catalytic reaction; Gelation; Acidity; Conversion; Exfoliation; Mesoporosity; Hydrolysis; Heterogeneous catalysis; Acids; Sol gel process; Surface area; Alumina; Catalyst
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2011.05.037

[Display omitted] ► New silica/alumina–clay heterostructures prepared by an innovative approach. ► Soft chemical route for delamination of layered silicates. ► Micro and mesoporous silica/alumina–clay heterostructures with high surface areas. ► Generation of acid catalysts. ► Clay heterostructures active for the synthesis of p-cymene from limonene. New delaminated porous silica/alumina–clay heterostructures have been prepared by an innovative approach involving the use of the Cloisite 30B commercial organoclay as starting material. The presence of alkylchains was liable for the controlled hydrolysis and polycondensation of a mixture of silicon and aluminum alkoxides previously incorporated within the interlayer space of clay. This soft chemical route was based on a spontaneous gelation in which the heterocoagulation process gives rise to exfoliation of the clay layers. Handling the synthetic parameters was possible to attain organoclay delamination by the inclusion of different silica/alumina compositions. The structural modification induced the creation of micro and mesoporous clay-based solids with high specific surface areas (ca. 650 m 2/g). The textural behavior of the clay changes noteworthy as the stack silicate layers were renewed into dispersed layers surrounded by well-dispersed nanoparticles of silica/alumina. These new porous silica/alumina solids can be described as “delaminated porous clay heterostructures (DPCHs)”, constituting a novel class of acid catalysts that compared to pillared-clays exhibit advantages such as the possibility of tuning of acidity by varying the Si/Al ratio. Their acid catalytic activity was evaluated for the synthesis of p-cymene from limonene, showing optimum conversion and efficient selectivity values.