Selective ring-opening of furfuryl alcohol to 1,5-pentanediol over Pt/aluminosilicates†

Abstract

Biomass-derived diols are key chemical building blocks for the sustainable chemical manufacturing of textiles and plastics, however their synthesis by a selective, scalable process from holocellulose is challenging. Furfuryl alcohol (FALC) is a potential precursor to 1,5-pentanediol (1,5-PeD) through acid-catalysed hydrogenolysis, and hence the impact of oxide support acidity on this reaction over Pt nanoparticles was investigated under batch and continuous flow in toluene. Platinum dispersed over weakly acidic fumed silica and mesoporous SBA-15 supports was almost inactive towards furfuryl alcohol at 150 °C and 10 bar H₂ and promoted decarbonylation and hydrodeoxygenation of FALC to furan and methyltetrahydrofuran, respectively. The introduction of Al³⁺ into silica supports, to form either an amorphous silica-aluminate (ASA) or mesoporous Al-SBA-15, selectively activated the cyclic ether bond at the C2–O position, increasing the specific activity for FALC conversion in continuous flow from 20 mmol g_Pt⁻¹ h⁻¹ (Pt/SBA-15) to 295 mmol g_Pt⁻¹ h⁻¹ (Pt/ASA), and 1,5-PeD selectivity from ∼25% (Pt/SBA-15) to 65% (Pt/ASA). This synergy between metal and acid sites resulted in a >25-fold enhancement in 1,5-PeD productivity, reaching 186 mmol g_Pt⁻¹ h⁻¹ for Pt/ASA, and was maintained for 7 h time-on-stream with negligible deactivation or metal leaching. A moderately acidic Pt/γ-Al₂O₃ catalyst exhibited reactivity intermediate between that of the Pt/silica and Pt/aluminosilicate catalysts. The yield of 1,5-PeD was directly proportional to the support acid site loading, indicating a common reaction mechanism. These findings demonstrate the striking promotion of metal catalysed hydrogenation that can be achieved through judicious support selection, and its translation from batch to flow with similar reaction kinetics.