Structure and acid-base properties of hexaaluminates

• Published in: Reaction kinetics and catalysis letters 2008-04, Vol.93 (2), p.375-387
• Main Authors: Bukhtiyarova, Marina V., Ivanova, Aleksandra S., Plyasova, Lyudmila M., Litvak, Galina S., Budneva, Anna A., Paukshtis, Evgenii A.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Industrial Chemistry/Chemical Engineering; Physical Chemistry
• ISSN: 0133-1736; 1588-2837
• DOI: 10.1007/s11144-008-5300-z

Hexaaluminates SrAl 12 O 19 , BaAl 12 O 19 and LaAl 11 O 18 were prepared by co-precipitation of soluble nitrates of Sr, Ba, or La and Al using NH 4 HCO 3 as a precipitating agent with subsequent calcination at 700–1400°C. The samples were characterized by adsorption methods, thermal analysis (TA and DTG), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy of adsorbed probe molecules (CO and CDCl 3 ). It was shown that calcination at 1200°C resulted in the formation of single-phase hexaaluminates in all the samples except for LaAl 11 O 18 , where an additional phase was found. The specific surface area of the samples was obtained in the range 16–22 m 2 /g. After the treatment at comparable conditions, the total concentrations of both surface Lewis acid sites and basic sites were found to increase in the series: BaAl 12 O 19 < SrAl 12 O 19 < LaAl 11 O 18 . However, the strongest basic sites were detected on the surface of BaAl 12 O 19 .