Silica-poly(styrenesulphonic acid) nanocomposites for the catalytic dehydration of xylose to furfural

• SiO2–PSSA nanocomposites with improved stability were prepared by sol–gel routes.
• Amino-functionalisation of the SiO2 is required for minimising the polymer leaching.
• These inorganic–organic nanohybrid can be used as acid catalysts.
• SiO2–PSSA nanocomposites present promising activity in conversion of xylose to furfural.

This investigation reports on the catalytic properties and hydrothermal stability of hybrid organic–inorganic nanocomposites based on aminopropyl-functionalised SiO2 and poly(styrenesulphonic acid) (PSSA). The nanocomposites were characterised by chemical analysis, thermogravimetric analysis (TGA), N2 adsorption–desorption isotherms, transmission electron microscopy (TEM), as well as Raman, Diffuse Reflectance Infrared Fourier Transform (DRIFT), X-ray Photoelectron (XPS) and 1H and 13C solid Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) spectroscopies. The results have proved that the presence of amino-functionalised silica results in stabilisation of the polymer molecules within the particle network of SiO2. The polymer is anchored to the silica matrix via electrostatic interactions between the sulphonic groups of the polymer molecules and the amino-functions present in the silica. These nanocomposites exhibited promising catalytic activity in xylose dehydration to furfural (at 443 K and after 5 h, ca. 90% xylose conversion, 65% furfural selectivity). When reused for several cycles, deactivation during the first run was observed due to polymer leaching. In successive runs catalytic properties remain stable.

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