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.

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.

Lignin reactions in oxygen delignification catalysed by Mn(II)-substituted molybdovanadophosphate polyanion

Holzforschung ◽  
2004 ◽  
Vol 58 (6) ◽  
pp. 640-649 ◽  
Author(s):  
Armindo Gaspar ◽  
Dmitry V. Evtuguin ◽  
Carlos Pascoal Neto
Keyword(s):  
Eucalyptus Globulus ◽  
Oxidative Degradation ◽  
Reaction System ◽  
Reaction Products ◽  
Oxygen Delignification ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Qualitative And Quantitative ◽  
Lignin Model ◽  
Oxidative Delignification

Abstract The lignin oxidation in the oxygen delignification/bleaching process catalysed by Mn(II) substituted heptamolybdopentavanadophosphate polyanion (HPA-5-MnII) was studied using monomeric lignin model compounds and Eucalyptus globulus dioxane lignin adsorbed on the bleached sulphite pulp. The analysis of reaction products after lignin models oxidation in the presence HPA-5-MnII and the parent heptamolybdopentavanadophosphate polyanion (HPA-5) showed similar qualitative and quantitative patterns, indicating the identical lignin oxidative delignification mechanisms with both catalysts. The higher delignification selectivity of the pulp in the reaction system HPA-5-MnII/O2 than with HPA-5/O2 was explained by the protective effect of MnII in the heteropolyanion towards oxidative degradation of polysaccharides. The study of lignin adsorbed on bleached sulphite pulp, in the HPA-5-MnII/O2 delignification system, showed the cleavage of β-O-4 linkages as the major contribution to the lignin depolymerisation. The formation of Cα-O-polysaccharide linkages in β-O-4 structures of lignin during the delignification was observed.

Lignin Degradation in Oxygen Delignification Catalysed by [PMo7V5O40]8- Polyanion. Part II. Study on Lignin Monomeric Model Compounds

Holzforschung ◽  
2000 ◽  
Vol 54 (5) ◽  
pp. 511-518 ◽  
Author(s):  
D.V. Evtuguin ◽  
C. Pascoal Neto ◽  
H. Carapuça ◽  
J. Soares
Keyword(s):  
Reaction System ◽  
Veratryl Alcohol ◽  
Vanillyl Alcohol ◽  
Coupling Reactions ◽  
Reaction Products ◽  
Oxygen Delignification ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Oxidation ◽  
Lignin Model

Summary Vanillyl and veratryl alcohols were used as monomeric lignin model compounds in experiments aiming to enhance the understanding of the lignin oxidation mechanisms involved in the oxygen delignification in acidic media catalysed by [PMo7V5O40]8− (HPA-5) heteropolyanion. Based on the model compound experiments, the first step of lignin oxidation is suggested to be a one-electron oxidation by the catalyst. This step is followed by coupling reactions and/or by further oxidation by the catalyst. The ratio of coupling/oxidation reaction products depends on the oxidation conditions and decreases with temperature raise. The higher oxidation rate of vanillyl alcohol as compared to the veratryl alcohol in the reaction system O2/HPA-5 was explained by the redox properties of the catalyst. The insufficiently high redox potential of HPA-5 did not allow the efficient oxidation of veratryl alcohol. The former was oxidised by VO2 + ions dissociated from the HPA-5 under the acidic conditions. The reactivity of different lignin structural units in the reaction system O2/HPA-5 was estimated by electrochemical methods using various lignin model compounds.

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.

Lignin to Value-Added Chemical Synthesis

2020 ◽  
Vol 16 ◽  
Author(s):  
Mahdieh Sharifi ◽  
Ramyakrishna Pothu ◽  
Rajender Boddula ◽  
Inamuddin
Keyword(s):  
Ionic Liquids ◽  
Lignocellulosic Biomass ◽  
Academic Research ◽  
Power Saving ◽  
Value Added ◽  
Glycerol Ether ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Biomass Activity ◽  
Lignin Model

Background: There is a developing demand for innovation in petroleum systems replacements. Towards this aim, lignocellulosic biomass suggested as a possible sustainable source for the manufacturing of fuels and produced chemicals. The aims of this paper are to investigate different kinds of β-O-4 lignin model compounds for the production of value-added chemicals in presence of ionic liquids. Especially, a cheap β-O-4 lignin model Guaiacol glycerol ether (GGE) (Guaifenesin) is introduced to produce valuable chemicals and novel products. Methods: Research related to chemical depolymerization of lignocellulosic biomass activity is reviewed, the notes from different methods such as thermal and microwave collected during at least 10 years. So, this collection provides a good source for academic research and it gives an efficient strategy for the manufacturing of novel value-added chemicals at an industrial scale. Results: This research presented that ionic liquid microwave-assisted is a power saving, cost efficient, fast reaction, and clean way with high selectively and purity for production of high value chemicals rather that conversional heating. Guaiacol and catechol are some of these valuable chemicals that is produced from β-O-4 lignin model compounds with high word demands that are capable to produce in industry scale. Conclusion: The β-O-4 lignin model compounds such as Guaiacol glycerol ether (GGE) (Guaifenesin) are good platform for developing food materials, perfumery, biorefinery, and pharmaceutical industry by ionic liquids-assisted lignin depolymerization method.

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