Lignin Utilization I. Kinetics of Base-Catalyzed Condensation Reactions of Lignin Model Compounds

1972 ◽  
Vol 2 (3) ◽  
pp. 271-275 ◽  
Author(s):  
G. E. Troughton ◽  
J. F. Manville
Keyword(s):  
Condensation Reaction ◽  
Activation Energies ◽  
The Self ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Temperature Range ◽  
Condensation Reactions ◽  
Lignin Model ◽  
Lignin Utilization ◽  
Kinetics Of

Rates of formation were measured for the base-catalyzed condensation reactions occurring between 4-alkylguaiacol compounds and their 6-methylol derivatives over the temperature range 85.5–100 °C. It was found that both the intercondensation reaction between the 4-alkylguaiacol compound and its 6-methylol derivative and the self-condensation reaction of the latter compound occurred at significant rates. In the 4-propylguaiacol – 4-methyl-6-methylolguaiacol system, the above two condensation reactions occurring in this system had the same activation energies, 35 kcal/mol. Similarly, in the 4-methylguaiacol – 4-propyl-6-methylolguaiacol system these two condensation reactions had equivalent activation energies, but slightly lower than in the former system, 32 kcal/mol. The kinetic results found for the model guaiacol compounds in this study demonstrate the possibility that a lignin-derived compound having more than one reactive position can be developed into a phenolic-type resin.

The self-condensation reactions of the lignin model compounds, vanillyl and veratryl alcohol

1980 ◽  
Vol 33 (4) ◽  
pp. 917 ◽  
Author(s):  
JA Hemmingson ◽  
G Leary
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Veratryl Alcohol ◽  
The Self ◽  
Benzyl Ether ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Condensation Reactions ◽  
Lignin Model

Self-condensation of the lignin model compounds vanillyl and veratryl alcohol leads to the formation of benzyl ether and diphenylmethane structures. It is suggested that these structures may be formed within lignin as it ages in the plant cell wall.

Study of kinetics of reaction of lignin model compounds with propylene oxide

Holzforschung ◽  
2008 ◽  
Vol 62 (2) ◽  
pp. 169-175 ◽  
Author(s):  
Krishna K. Pandey ◽  
Tapani Vuorinen
Keyword(s):  
Chemical Reaction ◽  
Propylene Oxide ◽  
Aqueous Media ◽  
Reaction Products ◽  
Model Compounds ◽  
Rapid Reduction ◽  
Visible Absorption ◽  
Lignin Model Compounds ◽  
Lignin Model ◽  
Kinetics Of

Abstract The etherification of phenolic groups has been found to inhibit photodegradation in wood and lignin rich pulps. The precise understanding of kinetics of chemical reaction between lignins or their model compounds and the etherifying agent is the first step for developing a viable modification procedure. In this study, we have investigated the reaction of lignin model compounds (namely, phenol and guaiacol) with propylene oxide in aqueous media. The kinetics of etherification reaction was studied under varying pH conditions in the temperature range 30–60°C. The etherified reaction products were characterized by gas chromatogram-mass spectrum (GC-MS). The extent of etherification of phenols and the rate of chemical reaction was followed by UV-Visible absorption spectroscopy. The reaction between lignin model compounds and propylene oxide was indicated by a rapid reduction in the absorbance accompanied by the development of a new band corresponding to etherified products. The reaction kinetics was investigated at pH ∼12 under the condition of excess concentration of propylene oxide. The reaction followed first order kinetics and rate constants increased linearly with an increase in the temperature and concentration of propylene oxide. The MS fragment data of reaction product support the proposed reaction scheme. The activation energy of the reaction of propylene oxide with phenol and guaiacol, calculated with the Arrhenius equation, was 56.2 kJ mol-1 and 45.4 kJ mol-1, respectively.

Radical Formation in Ozone Reactions with Lignin and Carbohydrate Model Compounds

Holzforschung ◽  
1999 ◽  
Vol 53 (3) ◽  
pp. 292-298 ◽  
Author(s):  
M. Ragnar ◽  
T. Eriksson ◽  
T. Reitberger
Keyword(s):  
Hydroxyl Radical ◽  
Metal Ions ◽  
Ph Dependence ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model ◽  
Kinetics Of ◽  
Radical Yield ◽  
Ozone Reactions ◽  
Ozone Bleaching

Summary Using different independent methods, the kinetics of ozone consumption and the initial radical yield in reactions of ozone with lignin and carbohydrate model compounds were investigated. It was demonstrated that ozone reacts with phenolates several orders of magnitude more rapidly than with corresponding undissociated phenols. The pH dependence of the radical yield does not completely follow the pK a-value of the phenols. In fact, the radical yield starts to increase at pH 3 for all the phenolic model compounds investigated. Several indications suggest that superoxide rather than the hydroxyl radical is initially formed when ozone reacts with lignin model compounds. In contrast to lignin model compounds no radicals were detected in ozone reactions with carbohydrate model compounds or olefins. On the basis of this study, it may be concluded that ozone bleaching should preferably be performed at pH 3 and at a higher consistency. No significant effect of metal ions was observed.

Comparison Activating Ability of Three Hydrogen Peroxide Activators

2013 ◽  
Vol 641-642 ◽  
pp. 215-218
Author(s):  
Sheng Guo ◽  
De Yi Huang ◽  
Ji Feng She ◽  
Xiang Qun Liang
Keyword(s):  
Hydrogen Peroxide ◽  
Half Life ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Bleaching Process ◽  
Peroxide Bleaching ◽  
Lignin Model ◽  
System 1 ◽  
Kinetics Of ◽  
H2o2 System

The bleaching efficiency of hydrogen peroxide can be promoted by using suitable activator. In our research, two methods were applied to compare the activating ability of three activators, TAED (tetraacetylethylenediamine), acetamide and dicyandiamide. The first part was hydrogen peroxide bleaching. TAED was excellent, because the brightness improvement was the maximum; the viscosity was acceptable. Acetamide was an applied activator in peroxide bleaching，for it could get same effects as TAED if the bleaching process had enough time and enough dosage. In the last part our study was about the kinetics of a lignin model compounds, acetovanillone, in peroxide-alone system, TAED/H2O2 system, acetamide/H2O2 system and dicyandiamide/H2O2 system. The rate constant, k and half-life period, t1/2 can be used to compare the rate of oxidation of acetovanilone. Compared to peroxide-alone system, three systems with activator and H2O2 could accelerate the reactions of hydrogen peroxide and acetovanillone. The t1/2 of TAED/H2O2 system was least of them. It was just 1/5 of t1/2 of peroxide-alone system, 1/4 of t1/2 of acetamide/H2O2 system and dicyandiamide/H2O2 system. The activating ability order of activators was: TAED> acetamide> dicyandiamide.

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