Cellulose proposed pathway

Scheme 2.—Proposed Pathway for the Biosynthesis of Cellulose in Algae.82...

Fig. 15 Proposed pathway for converting cellulose to glycolic acid. Adapted frran [156]...

Several products were also detected in base-degraded D-fructose solution acetoin (3-hydroxy-2-butanone 62), l-hydroxy-2-butanone, and 4-hydroxy-2-butanone. Three benzoquinones were found in the product mixture after sucrose had been heated at 110° in 5% NaOH these were 2-methylbenzoquinone, 2,3,5-trimethylbenzoquinone, and 2,5-dimethyl-benzoquinone (2,5-dimethyl-2,5-cyclohexadiene-l,4-dione 61). Compound 62 is of considerable interest, as 62 and butanedione (biacetyl 60) are involved in the formation of 61 and 2,5-dimethyl-l,4-benzenediol (63) by a reduction-oxidation pathway. This mechanism, shown in Scheme 10, will be discussed in a following section, as it has been proposed from results obtained from cellulose. 

Pyrolysis as defined is a process of thermal decomposition occurring in the absence of oxygen. Pyrolysis of biomass is a complicated multistage reaction for which many pathways and mechanisms have been proposed.551-558 The best known is the model developed by Broido and Shafizadeh559,560 for pyrolysis of cellulose that can be also applied, at least qualitatively, to whole biomass (Fig. 33.30). 

Biomass is a complex polymeric material and its thermal deconqiosition is a multistage complicated process. Many pathways and mechanisms have been proposed to illustrate/cxplain the fundamental steps in pyrolysis (e.g. 5, 6, 7, 8, 9, 10, 11, 12, 13). Broido-Shafizadeh type kinetic models are perhaps the most widely used for cellulose pyrolysis but they can be also applied, at least qualitatively, to the whole biomass (see Figure 1). 

It was determined that these ceriporic acids suppressed iron redox reactions to attenuate OH production by the Fenton reaction in the presence of iron reductants such as hydroquinone and cysteine. It was proposed that the suppression of the cellulolytic active oxygen species, OH, by this metabolite contributes to the selective lignin-degradation with a minimum loss of cellulose. The absolute configuration of ceriporic acids, their stereoselective biosynthetic pathway and the diversity of their metabolites have been largely discussed. 

Chemiluminescence has also been proposed as a novel tool in paper conservation studies [654,655]. CL phenomena can be used for assessing the thermal and oxidative degradation pathways of paper-based historical documents. In contrast with the usual accelerated degradation experiments in climatic chambers, measurement of isothermal CL is quick. The influence of all paper components (alkalinity, metal content, cellulose peroxides and carbonyl groups, moisture) and exposure to light will be investigated in the framework of the PAPYLUM project (ending October 2004). 

Cellulose (with phenol) Temperature 130°C Catalyst 0.4 g H SO (1.0 wt. % based on phenol) Cellulose/phenol ratio 1/3 An acid-catalyzed hydrolysis pathway of cellulose was proposed. The product composition was dependent on phenol/cellobiose ratio, catalyst concentration, temperature and reaction time. Lin et al. (2004)... 

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