The key role of pretreatment for the one-step and multi-step conversions of European lignocellulosic materials into furan compounds

Abstract

Nowadays, an increased interest from the chemical industry towards the furanic compounds production, renewable molecules alternatives to fossil molecules, which can be transformed into a wide range of chemicals and biopolymers. These molecules are produced following hexose and pentose dehydration. In this context, lignocellulosic biomass, owing to its richness in carbohydrates, notably cellulose and hemicellulose, can be the starting material for monosaccharide supply to be converted into bio-based products. Nevertheless, processing biomass is essential to overcome the recalcitrance of biomass, cellulose crystallinity, and lignin crosslinked structure. The previous reports describe only the furanic compound production from monosaccharides, without considering the starting raw material from which they would be extracted, and without paying attention to raw material pretreatment for the furan production pathway, nor the mass balance of the whole process. Taking account of these shortcomings, this review focuses, firstly, on the conversion potential of different European abundant lignocellulosic matrices into 5-hydroxymethyl furfural and 2-furfural based on their chemical composition. The second line of discussion is focused on the many technological approaches reported so far for the conversion of feedstocks into furan intermediates for polymer technology but highlighting those adopting the minimum possible steps and with the lowest possible environmental impact. The focus of this review is to providing an updated discussion of the important issues relevant to bringing chemically furan derivatives into a market context within a green European context.

Fig. 1. Main molecules derived from 5-HMF or 2-F exploited for the design of new biobased polymers and additives (non-exhaustive list).

Fig. 2. Hydrothermal conversion of d-glucose (A) and d-fructose (B) into 5-HMF and derivatives. Reaction intermediates and/or subsequent decomposition (or rearrangement) products are not mentioned.

Fig. 3. Multi-step conversion of lignocellulosic resources into furanic compounds. ILs stands for ionic liquids.

Fig. 4. Reaction pathways in the hydrothermal treatment of lignocellulosic biomass towards sugars and degradation products.

Fig. 5. Correlation of xylan solubilization/removal and biomass solubilization with hydrothermal (LHW) pretreatment temperature and time. Data are from ref. , , , , , .

Fig. 6. Correlation of xylan solubilization/removal and biomass solubilization with hydrothermal pretreatment conditions, expressed by log R_o and LSR. Data are from ref. , , , , , .

Fig. 7. Correlation of biomass solubilization with log R_o in dilute acid (H₂SO₄, wt%) HT pretreatment. Data are collected from ref. , , , .

Fig. 8. Furanic production via LHW pretreatment. Numbers correspond to acid concentrations: 1 : 0.5% v/v H₂SO₄, 2 : 1%v/v H₂SO₄, 3 : 1.6 w/v H₂SO₄, 4 : 400 g kg⁻¹ CH₃COOH, 5 : 3 wt% H₂SO₄, 6 : 0.5 wt% H₂SO₄, and 7 : 3% w/v H₂SO₄. Purple numbers correspond to furfural and blue numbers to 5-HMF. Data are from ref. , , , , , , , , , , and .

Fig. 9. General scheme for the preparation of furanic derivatives in IL-based processes.

Fig. 10. Schematic representation of the main interactions involved in the dissolution and activation for hydrolysis of polysaccharide fiber in ILs.

Fig. 11. Some examples of ILs used for the processing and transformation of lignocellulose.

Fig. 12. Some examples of DESs used for the processing and transformation of lignocellulose. ChCL: choline chloride, LA: lactic acid, CA: citric acid, N₂₂₂₂: tetraethylammonium, and EG: ethylene glycol.