Solid acid catalysis is an important class of reactions. The principal advantages of solid acid catalysts as compared to their corresponding fluid acids include minimal waste and ease of product separation. One type of these catalysts is based on aluminum bromide (Al2Br6), which is a stronger Lewis acid than Al2Cl6. In this report, Al(2)Br(6)is grafted on commercial mesoporous silica (CMS), SBA-15 and silica gel to create a solid catalyst similar to the silica-supported Al(2)Cl(6)superacid. These supported Al(2)Br(6)catalysts were characterized by NH3-Temperature Programmed Desorption (TPD), pyridine Diffuse Reflectance for Infrared Fourier Transform Spectroscopy (DRIFTS) and Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). Formation of acid sites was confirmed and quantified with NH3-TPD. Both Lewis and Bronsted sites were observed with DRIFTS using pyridine as a probe molecule. In addition, thermal stability of acid sites was also studied using DRIFTS.Al-27 MAS NMR analysis showed tetrahedral, pentahedral and octahedral co-ordination of Al, confirming that Al(2)Br(6)reacted with -OH groups on silica surface. Performance of these catalysts was evaluated using acid-catalyzed 1-butene isomerization. Conversion above 80% was observed at 200 degrees C, corresponding to thermodynamic equilibrium.
Publication Source (Journal or Book title)
Abedin, M. A., Kanitkar, S., Kumar, N., Wang, Z., Ding, K., Hutchings, G., & Spivey, J. J. (2020). Probing the Surface Acidity of Supported Aluminum Bromide Catalysts. CATALYSTS, 10 (8) https://doi.org/10.3390/catal10080869