Integrated reduction and acid-catalysed conversion of furfural in alcohol medium using Zr,Al-containing ordered micro/mesoporous silicates

Ordered porous silicates of the type TUD-1 and zeolite beta possessing zirconium and aluminium sites were evaluated as eco-friendly heterogeneous, multifunctional catalysts for the integrated reduction-acid conversion of furfural (Fur, industrially produced from hemicellulosic components of biomass) to useful bio-products, namely, furfuryl alcohol (FA), alkyl furfuryl ethers (FEs), alkyl levulinate esters (LEs), levulinic acid (LA), angelica lactones (AnLs), and ␥-valerolactone (GVL); the bio-products spectrum was obtained by GC × GC-ToFMS. Carrying out the one-pot conversion of Fur to bio-products using a multi-functional catalyst is challenging since various reactions are involved and it is difficult to control all of these to meet high reaction efficiencies and selectivities. Aiming at designing improved multifunctional catalysts for this reaction system, the TUD-1 and zeolite beta type silicates possessing zirconium and aluminium sites in different ratios were prepared and characterised on microstructural and molecular levels. Systematic characterisation, catalytic testing using 2-butanol as dual functional solvent-H-donor, and kinetic modelling studies were performed using the Zr,Al-containing micro- and mesoporous materials. Different steps of the overall reaction of Fur were studied separately starting from intermediate products using the same materials, which helped understand the influence of the material properties on reactivity of intermediates and reaction selectivity. Zr-sites of the silicate catalysts were essential for effectively initialising the overall process (reduction of Fur to FA), and for the reduction of LEs to GVL; the co-presence of Al-sites promoted acid-catalysed steps (FA to FEs, LEs, AnLs, LA). The good stability of the catalysts was verified by catalytic and characterisation studies of the spent catalysts.