The
interactions of the C4 sugar, erythrose, with various metal
oxides (γ-Al2O3, CeO2, Nb2O5, SiO2, SnO2, TiO2, and ZrO2) were investigated using solid-state nuclear
magnetic resonance (SS-NMR) spectroscopy. The surface species created
by the impregnation of erythrose onto these oxides reveal a major
shift in the equilibrium between cyclic, linear, and hydrated erythrose
relative to the confirmations present in solution. Surface species
on SnO2, TiO2, and ZrO2 were most
significantly affected by the increase in temperature from 25 to 50
°C, while on γ-Al2O3, CeO2, Nb2O5, and SiO2, the effect was
minimal. This work reports the first application of NMR relaxometry
to study the interactions of erythrose with metal oxides. This was
done by measuring the rotating frame relaxation time for each moiety
at 25 to 50 °C revealing whether these groups interact strongly
or weakly with the oxide surfaces. The Lewis and Brønsted acidity
of the materials was characterized using pyridine adsorption followed
by FTIR spectroscopy. Various surface reaction pathways are proposed
based on the diverse array of surface species that formed. The results
provide insights into the trends in surface chemistry of sugars on
Lewis acidic, Brønsted acidic, redox active, and inert metal
oxide surfaces.