scholarly journals Kraft Process—Formation of Secoisolariciresinol Structures and Incorporation of Fatty Acids in Kraft Lignin

2021 ◽  
Author(s):  
Maarit H. Lahtinen ◽  
Joona Mikkilä ◽  
Kirsi S. Mikkonen ◽  
Ilkka Kilpeläinen
Keyword(s):  
Fatty Acids ◽  
Kraft Lignin ◽  
Kraft Process ◽  
Process Formation

Dissociation of Phenolic Groups in Kraft Lignin at Elevated Temperatures

Holzforschung ◽  
2000 ◽  
Vol 54 (5) ◽  
pp. 519-527 ◽  
Author(s):  
Magnus Norgren ◽  
Birger Lindström
Keyword(s):  
Molecular Weight ◽  
Elevated Temperatures ◽  
Kraft Lignin ◽  
Degree Of Dissociation ◽  
Molecular Weights ◽  
Kraft Process ◽  
Poisson Boltzmann ◽  
Dissociation Curves ◽  
Complete Dissociation ◽  
Good Agreement

Summary The dissociation of the phenolic groups in a polydisperse, low molecular weight kraft lignin (Indulin AT) was studied in alkaline aqueous solutions in the temperature interval 21–70 °C, using a UV-spectrophotometric method. It was found that at a constant concentration of hydroxide ions, the degree of dissociation was decreasing when the temperature was elevated. Dissociation curves and apparent pΚ 0 values were also calculated for the polydisperse sample at the same conditions, using the van't Hoff and the Poisson-Boltzmann equations. At degrees of dissociation exceeding α ≈ 0.4, the outcome of the theoretical approach showed to be in good agreement with the experimentally obtained results. Furthermore, calculations were performed for different molecular weights of kraft lignin and from this it was found that the apparent pΚ 0 is shifted to higher values by increasing molecular weight, due to an increased electrostatic attraction of the hydrogen ions, which is arising from a less curved surface. Predictions of the dissociation behavior at temperatures reached in the kraft process were performed and under these conditions, higher molecular weight lignin fragments seem never to reach the point of complete dissociation. It was also found that an increase in temperature results in phase separation in kraft lignin solutions with high ionic strengths and pH values close to the pΚ a of the phenolic groups.

scholarly journals Catalytic Liquefaction of Kraft Lignin with Solvothermal Approach

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 875
Author(s):  
Woldemichael Sebhat ◽  
Ayman El Roz ◽  
Pascal Fongarland ◽  
Léa Vilcocq ◽  
Laurent Djakovitch
Keyword(s):  
Palladium Catalysts ◽  
31P Nmr ◽  
Inert Atmosphere ◽  
Kraft Lignin ◽  
Chemical Transformations ◽  
Paper Pulp ◽  
Solid Catalysts ◽  
Kraft Process ◽  
The Impact ◽  
Water Alcohol

Lignin is a natural biopolymer present in lignocellulosic biomass. During paper pulp production with the Kraft process, it is solubilized and degraded in Kraft lignin and then burned to recover energy. In this paper, the solvolysis of Kraft lignin was studied in water and in water/alcohol mixtures to produce oligomers and monomers of interest, at mild temperatures (200–275 °C) under inert atmosphere. It was found that the presence of alcohol and the type of alcohol (methanol, ethanol, isopropanol) greatly influenced the amount of oligomers and monomers formed from lignin, reaching a maximum of 48 mg·glignin−1 of monomers with isopropanol as a co-solvent. The impact of the addition of various solid catalysts composed of a metal phase (Pd, Pt or Ru) supported on an oxide (Al2O3, TiO2, ZrO2) was investigated. In water, the yield in monomers was enhanced by the presence of a catalyst and particularly by Pd/ZrO2. However, with an alcoholic co-solvent, the catalyst only enhanced the formation of oligomers. Detailed characterizations of the products with FTIR, 31P-NMR, 1H-NMR and HSQC NMR were performed to elucidate the chemical transformations occurring during solvolysis. The nature of the active catalytic specie was also investigated by testing homogeneous palladium catalysts.

Fatty Acids and Glycerides

1979 ◽  
Vol 7 (4) ◽  
pp. 813-814
Author(s):  
J. L. HARWOOD
Keyword(s):  
Fatty Acids
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