Active Site Hydration Governs the Stability of Sn-Beta during Continuous Glucose Conversion

Abstract

The stability of Sn-Beta for the continuous upgrading of hexoses is improved dramatically upon the addition of small amounts of water to the methanol/sugar reaction feed, despite water itself being an unfavourable solvent. Herein, the molecular level origin of this effect is investigated. Spectroscopic studies of the catalytic materials pre-, post-and during operation, with operando UV-Vis, 119 Sn CPMG MAS NMR, DRIFTS-MS, TGA, TPD/O-MS and porosimetry, are coupled to additional kinetic studies, to generate detailed structure-activity-lifetime relationships. In doing so, we find that the addition of water influences two particular processesfouling and active site modification. However, mitigating the second is the most crucial role of water. Indeed, in the absence of water, the loss of Sn-OH and Si-OH sites occurs. Notably, these changes in active site hydration correlate to deactivation and reactivation of the system. The consequences of these findings, both for mechanistic understanding of the system in addition to the design of alternative regeneration methods, are also discussed.

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

“…4). As we recently demonstrated that loss of crystallinity and pore fouling are not important factors with respect to deactivation of Sn-Beta for glucose isomerisation in MeOH [18,19,21], different possible causes of deactivation must explain the lower stability observed at higher loadings of Sn.…”

“…to allow a systematic study to be performed in a relatively short period of time. Furthermore, utilising pure MeOH allows identification of which materials are intrinsically more stable to deactivation through the mechanisms we recently identified for Sn-Beta catalysis [21]. Catalyst particles of 63-75 µm were employed after pressing and sieving.…”

“…Notably, the use of small quantities of water has also been shown to be beneficial during methyl lactate production, as it favours hydrolysis of unreactive methyl fructosides into fructose, which is then able to undergo to retroaldol cleavage [20]. After a detailed investigation employing a variety of kinetic and spectroscopic experiments, it was found that the main role of water in mitigating the deactivation of Sn-Beta during glucose conversion was to preserve the hydrated environment surrounding the active Sn sites [21]. In fact, in the absence of water i.e.…”

Discovery and Exploration of the Efficient Acyclic Dehydration of Hexoses in Dimethyl Sulfoxide/Water

“…The formation of furanics, THA, 3-deoxy compounds, and retro-aldol products mirrorst he pathways catalyzed by Sn-containingz eolites at near 160 8C. [4b] The tuning of product distribution by water resembles recent discoveries of water [12] and alkali ion [13] effects at the active site of heterogeneous Sn IV catalysts under such industrially relevant conditions.…”

“…Biomass production from carbon dioxide exceeds 100 10 12 kg per year, [1] with an average carbohydrate content of nearly 75 %( in addition to 20 %l ignin and5 %o ther compound classes). [2] Contraryt oo ther renewable biomass, carbohydrates are obtainable as cheap bulk chemicals.…”