Thermodynamic parameters governing the stereoselective degradation of arylglycerol-B-aryl ether bonds in milled wood lignin under kraft pulping conditions
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Behzad C. Ahvazi
Abstract
During this investigation, softwood (picea mariana) milled wood lignin was subjected to kraft pulping conditions at the temperature range 100-160 oC, for variable lengths of time. After quantitative isolation of the treated lignins, they were subjected to 31PNMR analyses which allowed the absolute rates of scission of the erythro and thewo diastereomers of the arylglycerol-B-aryl ether structures present in lignin to be derived.The plots of the kinetic data revealed that two kinetic regimes operate i.e. an initial fast phase that is followed by another slower phase. In agreement with previous accounts, the rate constants for these scission reactions were found to follow a pseudo-first-order rate law, during both phases. Rate constant data obtained during this effort, invariably indicated that the erythro isomers of the R-0-4 units of softwood milled wood lignin cleave faster than their thr-eo counterparts during both phases. At elevated temperatures (160 "C) the difference was found to be augmented. The general stability of the threo diastereomers toward kraft pulping seems to be the manifestation of a considerably slower reaction of the pulping reagents with the threo diastereomers of the B-aryl ethers. Arrhenius and Eyring plots o i these data supplied the complete profile of thermodynamic parameters governing this commercially important ether scission reaction.
© 2018 by Walter de Gruyter Berlin/Boston
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- The steady-state compressibility of saturated fibre webs at low pressures
- Dynamic simulation of a thermomechanical pulp refiner
- Identification of carton board qualities using gas chromatography or gas sensitive sensors in combination with multivariate data analysis
- Thermodynamic parameters governing the stereoselective degradation of arylglycerol-B-aryl ether bonds in milled wood lignin under kraft pulping conditions
- Calendering of coated paper and board in an extended soft nip
- List of dissertations in the field of pulp and paper 1996 (previously not published) and 1997
- Annual index for 1997
Artikel in diesem Heft
- Lamellar cracks, do they appear during radial compression of wood?
- Characterization of surfaces of CTMP fibers using inverse gas chromatography combined with multivariate data analysis
- Residual phase lignin in haft cooking related to the conditions in the cook
- Fibre characteristics and paper properties of formic acid / peroxyformic acid birch pulps
- Pulp washing: Influence of temperature on lignin leaching from kraft pulps
- Effect of headbox slice geometry during the stratified forming of woodfree paper
- Surface characterization of a rosin sizing agent in paper by means of EPMA, ESCA and TOF-SIMS
- The steady-state compressibility of saturated fibre webs at low pressures
- Dynamic simulation of a thermomechanical pulp refiner
- Identification of carton board qualities using gas chromatography or gas sensitive sensors in combination with multivariate data analysis
- Thermodynamic parameters governing the stereoselective degradation of arylglycerol-B-aryl ether bonds in milled wood lignin under kraft pulping conditions
- Calendering of coated paper and board in an extended soft nip
- List of dissertations in the field of pulp and paper 1996 (previously not published) and 1997
- Annual index for 1997
