Preparation of a composite γ-zirconium phosphate-silica with large specific surface and its first characterisation as acid catalyst

Abstract A composite of γ-zirconium phosphate (γ-ZrP) and silica (40% in weight of γ-ZrP) was prepared by hydrolysis of tetraethylsilicate in the presence of exfoliated γ-ZrP. The exfoliation of γ-ZrP was obtained in 1:1 (v/v) acetone/water solution at 80°C. The presence of silica prevented the re-aggregation of the exfoliated γ-ZrP lamellae. After heating at 650°C, the greater part of γ-ZrP was present in the composite as bilamellar packets of zirconium phosphate acid pyrophosphate while about 20% was transformed into α-Zr(O 3 POH) 2 . The surface acid POH groups of these lamellar species (about 1.1 meq. g −1 ) were not destroyed by thermal treatment up to 750°C. The composite exhibited a specific surface area of 421 m 2  g −1 of which about 191 m 2  g −1 was attributable to exfoliated lamellae of zirconium phosphate. The catalytic properties of the composite were preliminarily investigated for the conversion of ethylbenzene to styrene at different temperatures and different EB/O(air) ratios as a function of the contact time. The results are compared with pure γ-ZrP calcined at 650°C. Catalytic activity was strongly influenced by the total amount of the surface acidic groups of the samples. The γ-ZrP/SiO 2 composite showed a higher conversion rate (about five times) than calcined γ-ZrP.