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

Abstract

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 119 Sn 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.

Stoichiometric active site modification observed by alkali ion titrations of Sn-Beta

“…The expected cause is the formation of catalytically inactive extra-framework SnO 2 , for which the formation at high tin loadings is well known and was confirmed by XRD ( Figure S2) and by solid state 119 Sn MAS NMR (Figure 4). 31,32 Here, significant amounts of SnO 2 (with an intense signal near -600 ppm) was observed in addition to hydrated framework sites yielding a broad signal near -700 ppm. In contrast, only a small signal for extra-framework SnO 2 is observed for the Si/Sn 50 ARTICLE Journal Name 4 | J.…”

Zeolite (In)Stability under Aqueous or Steaming Conditions

“…[32,40] Similar ratios (10-40 times) in water uptake between Ti-BEA(OH) (postsynthetically exchanged in a dealuminated BEA zeolite) and Ti-BEA(F) samples were reported recently by Cordon et al [41] Such a drastic change in hydrophilicity due to synthetic procedure has been also confirmed for Ti-BEA samples. [39,42] Large hydrophilicity changes were convincingly assigned to differences in silanol densities, [41] showing that a larger silanol density results in larger water uptakes at low water vapor pressures (p/p 0 = 0-0.3). It has been demonstrated for Ti-BEA by Hoeven et al that even water sorption capacities (p/p 0 > 0.8) are proportional to silanol densities and that titanium content plays a much weaker role in water adsorption than the silanol defects.…”

Emphasis on the Properties of Metal‐Containing Zeolites Operating Outside the Comfort Zone of Current Heterogeneous Catalytic Reactions

“…The presence of water minimizes the accumulation of carbonaceous residues in the pores and reduces the loss of Sn‐OH and Si‐OH groups, that is, minimizing changes to the coordination sphere of active sites . Investigation of the preparation method and Sn loading for continuous operation in MeOH has also been investigated …”