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

• Published in: Applied catalysis. A, General Vol. 218; no. 1; pp. 219 - 228
• Main Authors: Alberti, G., Cavalaglio, S., Marmottini, F., Matusek, K., Megyeri, J., Szirtes, L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25-09-2001; Elsevier
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Ethylbenzene; Exact sciences and technology; General and physical chemistry; Oxidative dehydrogenation; Phosphate; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zirconium; Zirconium; Ethylbenzene; Catalysis; Oxidative dehydrogenation; Phosphate; Mixed catalyst; Catalytic reaction; Hydrocarbon; Catalyst selectivity; Transition metal Compounds; Acidic site; Experimental study; Zirconium phosphate; Exfoliation; Heterogeneous catalysis; Dehydrogenation; Preparation; Silicon Oxides; Oxidation; Kinetic parameter; Surface area
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/S0926-860X(01)00648-2

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
3POH)
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.