Pyrolysis of lignin

Figure 53 Antals tentative reaction tree of the pyrolysis of lignin [67].

A catalog of degradation products from the analytical pyrolysis of lignin has been published recently (Faix et al. 1990a,b). The compilation comprises retention time data and the complete mass spectra of 82 compounds. 

Pyrolysis of lignin models compared to ion fragments formation. 

Pyrolysis of lignin generates gases, tar, and char with yields depending on the lignin type and pyrolytic conditions. A typical result for kraft lignin pyrolysed at 650° C is shown in Table 9.1.2. 

Pyrolysis of lignin in the presence of acids, bases, or salts. 

Pyrolysis of lignin and wood at 650°C yields as pyrolysis products phenols, aldehydes, ketones, acids, and alcohols, generally with the retention of original substituents (OH, OCH3) on the phenyl ring (Figure 8.4). ... 

In 1979, Martin et al. (2468a) not only reported the results of their own research on the generation of a variety of phenols during the pyrolysis of lignin derived from several sources but also reviewed the results of their own and earlier studies by other investigators on lignin pyrolysis. 

Figures. Contrast between plasma and thermal pyrolysis condensable volatile fraction (tars) produced in solvent free pyrolysis of lignin...

Yu YQ, Li XY, Su L, Zhang Y, Wang YJ, Zhang HZ (2012) The role of shape selectivity in catalytic fast pyrolysis of lignin with zeolite catalysts. Appl Catal A 447 115... 

Judging from the success of the analytical model in Section 7.4.3.1 to reproduce substituent effects on a//3-selectivities, we will soon be able to model the pyrolysis of lignin model compounds including a complete set of relevant reactions. In a future vision, the combination of hundreds of computational studies of model compounds in the kinetic simulation of biomass conversion will enable us to bridge the gap between molecular understanding and industrially applicable processing techniques. 

The composition of the vapors is unknown and, usually, it is estimated by mass spectrometry technique. There are different polymerized products which decompose sequentially into trimers, dimers, and monomers in the liquid and gas phases. For example, a study for determining the boiling point of monomers/dimers from pyrolysis of lignin and cellulose based on empirical correlations of petroleum fractions was conducted by Beckman et al. (1985). 

For the pyrolysis of lignin, the aromatics and phenols and their alkyl substituted fractions may be formed by recombination and cyclization reactions. 

Production of pitch fibers was first investigated in Japan. In 1963, Sugio Otani obtained pitch fibers by the pyrolysis of lignin and later of PVC pitch. The first commercial product was the fiber from a pitch derived from crude oil pyrolysis, produced by Kureha,... 

Increasing the activation temperature produces the decrease of the carbon yield due (i) to the pyrolysis of lignin up to 600 °C (ii) to the activation by KOH and K2CO3 that starts at 450-500°C. The dissociation of the two phenomena, pyrolysis and activation, is impossible because lignin have already reacted with KOH in some extent before pyrolysis finishes. 

For example, the main phenol with antioxidative and antimutagenic activities that occurs in crude canola oil is 2,6-dimethoxy-4-vinylphenol known as canolol, which is produced from syringic acids. The major products of caffeic acid pyrolysis at 225 °C are pyrocatechol, 4-vinylpyrocatechol and 4-ethylpyrocatechol (see Section 8.3.4). A more complex mixture of products arises by pyrolysis of lignin, in the smoke condensates used in the meat industry, more than 150 different phenols, and dozens of aromatic alcohols, phenolic acids and hydroxylated heterocyclic compounds have been identified. 

Jackson, M. A., Compton, D. L., Boateng, A. A. Screening heterogeneous catalysts for the pyrolysis of lignin. J Anal Appl Pyrolysis 2009,85,226-230. 

To begin, we discuss the upgrading of bio-oils by means of cracking and hydrodeoxygenatioa This will be followed by upgrading pyrolysis vapors and cataljdic pyrolysis. Finally, a short overview of catalytic fast pyrolysis of lignin will close this part of the chapter. 

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