Renewably sourced phenolic resins from lignin bio‐oil

Abstract

Traditional lignin pyrolysis generates a bio-oil with a complex mixture of alkyl-functionalized guaiacol and syringol monomers that have limited utility to completely replace phenol in resins. In this work, formate assisted fast pyrolysis (FAsP) of lignin yielded a bio-oil consisting of alkylated phenol compounds, due to deoxyhydrogenation, that was used to synthesize phenol/formaldehyde resins. A solvent extraction method was developed to concentrate the phenolics in the extract to yield a phenol rich monomer mixture. Phenolic resins were synthesized using phenol (phenol resin), FAsP bio-oil (oil resin), and an extract mimic (mimic resin) that was prepared to resemble the extract after further purification. All three phenolic sources could synthesize novolac resins with reactive sites remaining for subsequent resin curing. Differential scanning calorimetry and thermogravimetric analysis of the three resins revealed similar thermal and decomposition behavior of phenol and the mimic resins, while the oil resin was less stable. Resins were cured with hexamethylenetetramine and the mimic resin demonstrated improved curing energies compared to the oil resin. The adhesive strength of the mimic resin was found to be superior to that of the oil resins. These results confirmed that extracting a mixture of substituted aromatics from FAsP bio-oil could synthesize resins with properties similar to those from phenol and improved over the parent bio-oil.

Limited life cycle and cost assessment for the bioconversion of lignin‐derived aromatics into adipic acid

“…To apply both products in the industry their use must be characterized as a drop‐in product. Phenol–formaldehyde resins produced from the organic phase with increased homogeneity are expected to have an appropriate reactivity and reduced viscosity (Vithanage et al, 2017). For adipic acid, which is produced from monomeric aromatics present in the aqueous phase, the presence of methylated adipic acid from o ‐, m ‐, and p ‐cresol must be elucidated (Kohlstedt et al, 2018).…”

“…However, the presence of the methoxy-phenols such as syringol, guaiacol, and catechol causes a resin having diminished properties as lower reactivity and a higher viscosity due to their limited cross-linking reactivity with formaldehyde. As shown in this study, syringol is not present in bio-oil from softwood kraft and organosolv lignin (de Wild, Huijgen, Kloekhorst, Chowdan, & Heeres, 2017), and the application of hydrodeoxygenation reduces the concentration of guaiacol ( Vispute, Zhang, Sanna, Xiao, & Huber, 2010;Vithanage et al, 2017). To date, the resulting aqueous phase only generates a limited value, for example, as a source of biogas via anaerobic digestion/wastewater treatment of the low molecular weight substances present such as acetic acid and methanol.…”

Bio-oil yield and quality enhancement through fast pyrolysis and fractional condensation concepts

“…The bio-oil contains about 300 organic compounds, where different functional groups such as organic acids, ketones, aldehydes, esters, phenols, furans, and anhydrous sugars can be found (Pittman et al, 2012;Ren et al, 2016). Pyrolytic oil can be used for electricity production, heating (Fu et al, 2017;Kalargaris et al, 2017), and chemical extraction (Onorevoli et al, 2017;Vithanage et al, 2017). The production cost per energy unit of pyrolytic biooil is around $4.04 -$21.73/GJ (Mirkouei et al, 2017;Treedet and Suntivarakorn, 2018).…”

Preparation of highly phenol substituted bio‐oil–phenol–formaldehyde adhesives with enhanced bonding performance using furfural as crosslinking agent

“…However, phenol is derived from nonrenewable petroleum. Increasing attention has been paid to finding suitable and renewable aromatic units to substitute for the petroleum‐based phenol . Therefore, it is urgent to develop sustainable methods to prepare phenolic resin.…”