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Lignin-phenol-formaldehyde (LPF) resoles were prepared using different types of lignin at various levels of phenol replacement by lignin (0 to 40 wt.%). Adhesive properties including thermal behavior as determined by differential scanning calorimetry (DSC), time-dependent development of bond strength during hot pressing as determined by automated bonding evaluation system (ABES), tensile shear strength of solid beech wood lapjoints, and free formaldehyde content of the adhesives were investigated. Preparation of phenol-formaldehyde (PF) resole was accomplished using molar ratios of formaldehyde/phenol and NaOH/phenol of 2.5 and 0.3, respectively. Four different types of technical lignins were studied: Sarkanda grass soda lignin, wheat straw soda lignin, pine kraft lignin, and beech organosolv lignin. The synthesis of the resoles was optimized for 20 and 40 wt.% phenol replacement by lignin. Increasing substitution of phenol resulted in faster gain of LPF viscosity for all studied lignins. The best curing performances of the LPF resoles were observed for pine kraft lignin at both 20 and 40% phenol replacement. The amount of formaldehyde not consumed during cooking increased with increasing level of phenol replacement. However, no differences in free formaldehyde content were observed between the different lignin samples at comparable levels of phenol replacement.

Hydroxymethylfurfural (HMF) is a high‐value platform chemical derived from renewable resources. In recent years, considerable efforts have been made to produce HMF also at industrial scale, which still faces some challenges regarding yield as well as sustainable and economic process designs. This critical Review evaluates the industrial process development of sustainable biomass conversion to HMF. Qualitative and quantitative guidelines are defined for the technological assessment of the processes described in patent literature. The formation of side products, difficulties in the separation and purification of HMF as well as catalyst regeneration were identified as major challenges in the HMF production. A first small‐scale, commercial HMF production plant with a capacity of 300 t HMF per year has been operating in Switzerland since 2014.

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Oxidation of cellulose with periodate under aqueous conditions yields dialdehyde cellulose, a promising functional cellulose derivative. The main obstacles for this oxidation have been its slow kinetics and the dilute reaction conditions, requiring considerable amounts of water and energy. In this study, these drawbacks are overcome by conducting the oxidation at high cellulosic pulp consistency with a cellulose/water weight ratio of 1:4. The oxidizer, cellulose, and water are efficiently mixed in a ball mill. Oxidation occurs mostly in the subsequent step, during the resting time (no further milling/mixing is required). The reaction and resource efficiency of the process are optimized by experimental design and a maximum aldehyde content of 8 mmol g−1 is obtained with a periodate/cellulose molar ratio of 1.25, a milling time of 2 min, and a resting time of 8 h. The developed method allows fine tuning of the oxidation level and is a key step towards the sustainable periodate oxidation of cellulose also on larger scale.

Lignin phenol formaldehyde (LPF) resols were produced using depolymerized lignin fractions at various levels of phenol substitution (50 to 70 wt %). To produce monomeric-rich (BCD-oil) and oligomeric (BCD-oligomers) bio-based phenolic compounds, softwood kraft lignin was base-catalysed degraded. These base-catalysed depolymerized (BCD) building blocks were further used to substitute phenol in the synthesis of phenolic resins and were characterized in detail (such as viscosity, free formaldehyde and phenol content, chemical composition, curing and bonding behaviour). The adhesive properties were compared to a phenol formaldehyde (PF) reference resin and a LPF with untreated kraft lignin. The resins synthesized with the two depolymerized lignin types differ significantly from each other with increasing phenol substitution. While with LPF-BCD-oligomers the viscosity increases and the bonding strength is not effected by increasing lignin content in the resin, a reduction of these properties could be observed with LPF-BCD-oil. Furthermore, LPF-BCD-oil showed similar curing behaviour and ultimate strength as the reference LPF. Adhesive bonds made using LPF-BCD-oligomers exhibited similar strength to those made using PF. Compared to the reference resins, it has been demonstrated that modified renewable lignin based phenolic components can be an equally performing alternative to phenol even for high degrees of substitution of 70%.

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