Basic silica catalysts for the efficient dehydration of biomass-derived compounds – Elucidating structure-activity relationships for Na2O/SiO2-type materials

Abstract

The gas-phase dehydration of biomass-derived N-(2-hydroxyethyl)-2-pyrrolidone by Na2O/SiO2-type catalysts propounds a promising route to polyvinylpyrrolidone, a high-value polymer. Thus, an optimization of said catalysts via variations of the silica parent, sodium precursor and sodium loading was performed. The combination of resulting performance data with in-depth characterization via FTIR spectroscopy, CO2-TPD and physisorption techniques leads to a clear structure-activity correlation. Most importantly, catalyst activity is promoted by a balance between weak basic sites (Si-ONa) and surface hydroxyls (Si-OH), which comes about through ion exchanging a fraction of the initial silanol in mild conditions. The optimal synthesis procedure and recipe are thus a function of the type of parent silica. With this renewed molecular understanding of the reaction, the scope of application of the Na2O/SiO2 materials was expanded to the dehydration of other biomass-derived chemicals of interest in the polymer industry.