Influence of Composition and Preparation Method on the Continuous Performance of Sn-Beta for Glucose-Fructose Isomerisation

The stability, activity and selectivity of various Sn-Beta catalysts are investigated to identify how the composition of the catalyst, in addition to its method of preparation, impact its ability to continuously isomerise glucose to fructose. Increasing the Sn loading in post-synthetically prepared catalysts leads to a decrease of both activity and stability. Accordingly, materials containing dilute amounts of Sn appear to be most suitable for continuous operation. Furthermore, the method of preparation has a profound impact on the overall performance of the catalyst. In fact, preparation of Sn-Beta by hydrothermal synthesis results in improvements of both activity and stability, with respect to the post-synthetic preparation of an otherwise-analogous material. The improved resistance of hydrothermal Sn-Beta is attributed, through a combination of operando UV–Vis, TPD-MS and vapour adsorption isotherms, to its greater resistance to deactivation by methanol (the reaction solvent). Complementary 119Sn CPMG MAS NMR experiments also indicate the presence of different Sn sites in the hydrothermal material, which, alongside the presence of a less adsorptive siliceous matrix, may be intrinsically less prone to solvent interaction than those present in post-synthetic Sn-Beta.