摘要:

Methylation analysis was used to investigate the bonds to lignin of the carbohydrates remaining after enzymatic hydrolysis and alkaline reduction of ball-milled loblolly pine wood and red pine compression wood. The carbohydrates exist as oligomeric chains with degrees of polymerization of 7–14. Approximately one sugar unit per oligomer chain is bonded to lignin. Bonding at C-6 of the hexose units is favored, and the arabinose is bonded exclusively at C-5. Galactan and arabinan are structurally of the 1–4 and 1–5 linked types respectively, characteristic of the so-called “pectic group substances.”

ISSN:0277-3813    

DOI:10.1080/02773818208085116

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The depolymerization of hydrochloric acid sweetgum lignin by hydrotreating in hydrogen-donor solvents in the temperature range of 375–425°C (707–797°F) has been studied. Analysis of the phenolic products showed that the principal depolymerization reactions were the cleavage of ether and Cα–Cβbonds. A maximum yield of approximately 11% monomeric phenols was obtained, with the intermediate compounds for the most part being further degraded into gases and neutral products. The reaction kinetics were found to be first order, with an activation energy of 24 Kcal (100 kJ). The addition of a heterogeneous catalyst did not increase the yield of monomeric phenols.

ISSN:0277-3813    

DOI:10.1080/02773818208085117

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

HC1 lignin, prepared from sweetgum wood(Liquidambar styraclfluaL.) by hydrolysis of the carbohydrates with super concentrated hydrochloric acid, was reductively depolymerized in alkali using various heterogeneous catalysts. A maximum yield of 18% distillable products was obtained by this alkaline hydrolysis-catalytic hydrogenolysis treatment. Surprisingly, it was found that few covalent bonds were being cleaved by the catalysts, with the majority of the bonds having been broken by alkaline hydrolysis. GC analysis showed that a large portion of the monomeric phenolic products had been dealkylated at the para-position. A reaction scheme has been proposed to explain the alkaline hydrolysis mechanism involved. Lignin tar, which was formed by alkaline hydrolysis of HC1 lignin alone, was subjected to subsequent reduction using selected catalysts. This sequential hydrolysis-hydrogenolysis treatment caused the lignin to recondense, apparently because of the inability of the catalysts to reduce groups which are capable of polymerizing together.

ISSN:0277-3813    

DOI:10.1080/02773818208085118

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

9,10-Anthraquinone (AQ), anthraquinone-2-sulfonic acid (AMS), and anthraquinone-1-acetic acid (AMA) were determined in alkaline pulping liquors by adsorption on Amberlite XAD-2 from liquors diluted with ethanol (AQ) or water (AMS and AMA). After washing, AQ was eluted with 99% ethanol, AMS with acidified 25% ethanol and AMA with alkaline 25% ethanol.

ISSN:0277-3813    

DOI:10.1080/02773818208085119

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A series of substituted anthraquinones has been prepared to determine the influence of hydrophilic and hydrophobic substituents on the efficiency of delignification in soda pulping of Douglas fir. Regardless of redox potential and proximity to the ring system of the parent anthraquinone, carboxyl groups strongly diminish the activity of AQ. This effect is believed to be the result of increased hydrophilicity of the carboxyl derivatives relative to unsubstituted anthraquinone. Conversely, nonpolar hydrocarbon sidechains tend to increase the activity of anthraquinone in soda pulping. These effects suggest that adsorption phenomena may play a strong role in additive performance, and that hydrophobic substituents tend to concentrate the additive in the wood phase, while hydrophilic derivatives tend to remain in the liquid phase.

ISSN:0277-3813    

DOI:10.1080/02773818208085120

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The rapid delignification rates associated with anthraquinone-alkaline pulping could be due to the formation and reactions of lignin qulnonemethide-anthrahydroquinone (QM-AHQ) adducts. The chemistry of some simple QM-AHQ adducts is examined here. Upon heating in aqueous alkali, the QM-AHQ adducts fragment to QMs and AHQ. At 100° the adducts are reduced by AHQ dianion to afford QM-anthrone adducts and anthraquinone. At typical pulping temperatures (173°), the adducts are extensively, but not completely, decomposed, releasing AHQ and/or anthraquinone.

ISSN:0277-3813    

DOI:10.1080/02773818208085121

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Anthrahydroquinone and anthrone readily react with stabilised quinone methides in alkaline solution to give 10-substituted oxan thrones and an thrones respectively. Similarly, reaction of a vinyl-substituted quinone methide gives the corresponding anthrone, both as the keto and enol adducts, and the substituted oxanthrone. Whilst both forms of the substituted anthrone can be partially converted to 3-arylbenzanthronea analogous to 3-guaiacylbenzanthrone formed during pulping, the oxanthrone adduct affords practically none of thi3 product. This indicates that it is reduction of anthraquinone to its anthrone oxidation state which results in benzanthrone formation during pulping.

ISSN:0277-3813    

DOI:10.1080/02773818208085122

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0277-3813    

DOI:10.1080/02773818208085115

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor