Versatile post-synthetic Sn incorporation into hierarchically porous BEA zeolite for glucose isomerization in 1-butanol

Abstract

Glucose isomerization in water has been widely investigated using Sn-BEA zeolites as Lewis acid catalysts. Recently, it was reported that the use of 1-butanol as a solvent can be advantageous in terms of enhanced fructose yields and easy product separation. In this study, we investigated glucose isomerization both in water and 1-butanol over a series of Sn-BEA zeolites including one directly crystallized in a Fmedium and the others prepared by post-synthetic Sn incorporation. The directly crystallized Sn-BEA showed high fructose yield (34%) in water because of its defect-free hydrophobic nature, which suppressed the inhibition of Lewis acid sites by water. However, in 1-butanol, it showed the lowest fructose yield and fastest deactivation among the catalysts, because of its extra-large zeolite crystallites (ca. 15 mu m) causing mass transfer limitation and undesired side reactions. The Sn-BEA catalysts prepared by post-synthetic Sn incorporation showed limited catalytic performance in water because of hydroxyl defects. However, they showed superior performances in 1-butanol because of the much smaller crystallites and enhanced mass transfer. In particular, the hierarchical Sn-BEA having 10-20 nm crystallites and significant intercrystalline mesoporosity showed a very large fructose yield (55%) that are difficult to achieve in typical aqueous-phase glucose isomerization (<35%).