A Simple Two-Step Method for the Selective Conversion of Hemicellulose in Pubescens to Furfural

Abstract

A two-step method was adopted to produce furfural from the selective dissolution and conversion of hemicellulose in pubescens. First, in GVL­(γ-valerolactone)-H2O co-solvent at 160 °C, H2O promoted the cleavage of chemical bonds linking hemicellulose, lignin, and cellulose, and GVL further helped the co-dissolution of hemicellulose (93.6 wt %) and lignin derivatives (80.2 wt %), leaving a high purity cellulose (83.3 wt %). Heating to 200 °C, the liquid system obtained with NaCl and THF added, achieved the maximum yield of 76.9 mol % with 82.2% selectivity to furfural based on the moles of converted hemicellulose using a 5 wt % pubescens to solvent ratio. It was demonstrated that NaCl with GVL promoted the depolymerization of oligomers to small molecular products (Mw < 150 Da), while the co-contribution of NaCl and co-solvent improved the selectivity to furfural. Cl– could interact strongly with C-OH-2,3,4 of the xylose unit, and the dehydration of xylose to form furfural might first occur on C-OH-4 of xylose, then on C-OH-2,3 of xylose, which enhanced the dehydration and ring open reaction via the cleavage of C1–O6 bonds, then promoted the formation of furfural by inhibiting the retro-aldol reaction to form lactic acid. The co-contribution of NaCl and co-solvent was benefical not only for the selective conversion of the mixture containing hemicellulose-derived monomers and oligomers to furfural but also for obtaining a lower molecular weight lignin derivatives (150–500 Da) that could be further used.

pH‐Controlled Efficient Conversion of Hemicellulose to Furfural Using Choline‐Based Deep Eutectic Solvents as Catalysts

“…The isolated yield of furfural was determined comparing its peak area with that of the areas obtained by previously injecting standard furfural solutions in water of known concentration. The purity of furfural obtained was further confirmed by 1 H and 13 C NMR spectroscopy, which was found to be in full agreement with the data previously reported in literature [43] …”

“…Additionally, the development of various reaction systems for the synthesis of furfural has also been thoroughly investigated. Various approaches for the production of furfural have been reported in the literature, mainly focusing on the development of different catalytic systems including mineral acids, [11,12] metal salts, [13–15] zeolites, [16–18] Amberlyst, [19] and heterogeneous solid acid catalysts either in monophasic or biphasic systems, such as H 2 SO 4 in water/THF, [20] metal halides in water/toluene, [21] and SAPO‐44 in water/toluene [22] . However, the complication with the reported methodologies is their tedious reaction protocols.…”

Hydrolysis of Hemicellulose and Derivatives—A Review of Recent Advances in the Production of Furfural

“…Using metal salts, biphasic systems were developed making use of similar solvents as mentioned above. Isolation of hemicelluloses from Rubescens using a water-GVL biphasic system heated at 180°C was studied (Luo et al, 2017 ). The hemicelluloses rich lignin fraction was then warmed up in presence of NaCl and THF giving a furfural yield of 77%.…”

Acid‐Catalyzed Conversion of Carbohydrates into Value‐Added Small Molecules in Aqueous Media and Ionic Liquids

“…HMF may be produced through AlCl 3 ‐catalyzed transformation of biomass in a biphasic system, H 2 O–NaCl/THF, under microwave heating . These conditions enable a range of lignocellulosic materials (corn stover, pine wood, grass, poplar) to be transformed into HMF in high yields (Table ), and this solvent system can also be used to produce furfural in high yield (77 %) . Additionally, furfural was obtained as a second major product in impressive yields of up to 65 % (based on the weight of pentose in the substrate), which is in the order required for a commercializable processes .…”

“…[79,80] These conditions enable ar ange of lignocellulosic materials (corn stover,p ine wood,g rass, poplar) to be transformed into HMF in high yields (Table 1), and this solvents ystem can also be used to produce furfural in high yield (77 %). [81] Additionally,f urfural was obtained as as econd major product in impressivey ields of up to 65 %( based on the weighto fp entose in the substrate), which is in the order requiredf or ac ommercializable processes. [82] The appearance of furfural is ascribed to the presence of hemicellulose in the lignocellulosic biomass, which consists primarily of d-pentose sugars (xylose, arabinose, rhamnose, etc.)…”