Novel hydrogenation reaction of renewable furfural into furfuryl alcohol using highly efficient and selective water-soluble platinum catalysts modified with phosphines and nitrogen-containing ligands in green aqueous media

Abstract

The renewable platform chemical furfuryl alcohol (FOL) plays a pivotal role in the development of biorefineries and is manufactured by the catalytic hydrogenation reaction of furfural (FAL) which is, after bioethanol, the 2nd highest demanded biomass downstream product. High catalytic activities (TOF > 20000 h⁻¹) with essentially quantitative selectivities to the desired product FOL (> 99 mol%) have been achieved in the novel hydrogenation of FAL employing water-soluble platinum catalysts modified with the industrially applied benchmark ligand trisulfonated triphenylphoshine (TPPTS) under mild and neutral conditions in the green and sustainable aqueous solvent. The apparent activation energy of the Pt/TPPTS catalyst amounts 4.7 kJ/mol. This usually low value points out the presence of a highly active platinum TPPTS catalytic system to convert efficiently the aldehyde moiety of FAL into an alcohol group to yield selectively FOL in water. Five recovery and recycling experiments of the Pt/TPPTS catalytic system showed that the catalyst possesses some stability and keeps its very high selectivity towards FOL in the aqueous solvent. The work disclosed here is consistent with six of the twelve principles of Green Chemistry which are: i) high atom economy i.e. low E-factor due to the clean incorporation of molecular hydrogen to the substrate FAL to yield selectively FOL, ii) use of innocuous solvents i.e. water, iii) use of renewable biomass-derived FAL, iv) use of catalytic reagents, v) designing safer chemicals because the products are bio-based value added chemicals, and vi) inherent safer chemistry for accident prevention because of the high heat capacity of the aqueous solvent which renders exothermic reactions such as hydrogenation reactions more safe especially in the large industrial scale.