RenFuel (Sweden)

Lignin is an abundant polymeric renewable material and thus a promising candidate for incorporation in various commercial thermoplastic polymers. One challenge is to increase the dispersibility of amphiphilic lignin in lipophilic thermoplastic polymers We altered Kraft lignin using widely available and renewable fatty acids, such as oleic acid, yielding more than 8 kg of lignin ester as a light brown powder. SEC showed a molecular weight of 5.8 kDa with a PDI = 3.80, while the Tg of the lignin ester was concluded to 70 °C. Furthermore, the lignin ester was incorporated (20%) into PLA, HDPE, and PP to establish the thermal and mechanical behavior of the blends. DSC and rheological measurements suggest that the lignin ester blends consist of a phase-separated system. The results demonstrate how esterification of lignin allows dispersion in all the evaluated thermoplastic polymers maintaining, to a large extent, the tensile properties of the original material. The impact strength of HDPE and PLA blends show substantial loss upon the addition of the lignin ester. Reconverting the acetic acid side stream into acetic anhydride and reusing the catalyst, the presented methodology can be scaled up to produce a lignin-based substitute to fossil materials.

Blackliquor (BL) from the kraft pulping process has been treatedat elevated temperatures (380 °C) in a batch reactor to givehigh yields of a bio oil comprising monomeric phenolic compounds thatwere soluble in organic solvents and mineral oil and a water fractionwith inorganic salts. The metal content in the product was <20ppm after a simple extraction step. A correlation between concentration,temperature, and reaction time with respect to yield of desired productwas found. At optimal reaction conditions (treating BL with 16 wt% dry substance at 380 °C for 20 min), the yield of extractableorganics was around 80% of the original lignin with less than 7% ofchar. The product was analyzed by gel permeable chromatography, massspectroscopy, nuclear magnetic resonance, elemental analysis, andinductively coupled plasma. It was found that a large fraction composedof mainly cresols, xylenols, and mesitols. This process provides apathway to convert a major waste stream from a pulp mill into a refineryfeed for fuel or chemical production, whereas at the same time theinorganic chemicals are recovered and can be returned back to thepulp mill.

Precipitated kraft lignin from black liquor was converted into green diesel in three steps. A mild Ni-catalyzed transfer hydrogenation/hydrogenolysis using 2-propanol generated a lignin residue in which the ethers, carbonyls, and olefins were reduced. An organocatalyzed esterification of the lignin residue with an in situ prepared tall oil fatty acid anhydride gave an esterified lignin residue that was soluble in light gas oil. The esterified lignin residue was coprocessed with light gas oil in a continous hydrotreater to produce a green diesel. This approach will enable the development of new techniques to process commercial lignin in existing oil refinery infrastructures to standardized transportation fuels in the future.