Thermally assisted hydrolysis and alkylation of lignins in the presence of tetra-alkylammonium hydroxides

Pyrolytic alkylation-gas chromatography-mass spectrometry of model polymers Further insights into the mechanism and scope of the technique

“…In agreement with the results reported by other authors, the pyrogram of DHP is somewhat similar to that of pine lignin (representative of softwood), composed exc1usively of guaiacyl units [6]. In the presence of TMAH, its behaviour (Fig.…”

“…The process is considered to be a thermally assisted hydrolysis followed by alkylation, rather than a true pyrolysis followed by 'in situ' alkylation of the products [1,2,6,9]. It is therefore different to the conventional pyrolysis where the pyrolysis compounds are generated from the macromolecular substances by bond breaking induced by heat only.…”

“…(TMAH) [1][2][3][4][5] and tetrabutylammonium hydroxide (TBAH) [6] has been introduced for the release of moieties bearing carboxyl groups from different polymers and macromolecules upon pyrolytic techniques. Use of the butylating reagent avoids one of the main limitations of pyrolytic methylation -its inability to distinguish between the methoxyl groups originally present in the macromolecule and the free hydroxyl groups that become methylated after the pyrolysis.…”

Effects of biological treatment on the chemical structure of dissolved lignin-related substances in effluent from thermomechanical pulping

“…The use of TMAH enables pyrolysis at a lower temperature (Challinor 2001;Hardell and Nilvebrant 1996), thus decreasing the formation of new compounds by thermal degradation and secondary reactions, which at conventional pyrolysis temperatures may lead to incorrect conclusions regarding the chemical structure of the polymer under study (Saint-Jimenez 1994). Methylation also enables the detection of carboxylic acids that otherwise, in conventional pyrolysis, would be eliminated by decarboxylation (Saiz-Jimenez 1994; Martin et al 1995). Hardell and Nilvebrant (1996) report 1-veratrylglycerol trimethyl ethers, obtained from β-ether linked units, as the main degradation products formed from lignins by THM, and the identification of such peaks also in the present experiment verified the lignin origin (β-O-4 ether bonds) of the investigated samples.…”

Structural Characterization of the Lignin in the Cortex and Pith of Elephant Grass (Pennisetum purpureum) Stems

“…Py/TMAH induces cleavage of alkyl aryl ether bonds in lignin and releases products similar to those obtained upon CuO alkaline degradation, including methylated hydroxybenzaldehydes (peaks 6, 12 and 18), hydroxyacetophenones (peaks 15 and 22) and hydroxybenzoic acids (peaks 10, 16 and 24). 13,14,49,50 As seen in Figure 2, Py/TMAH of the cortex and pith released high amounts (over 45% of the total peak area) of the fully methylated derivative of p-coumaric acid, i.e., trans-3-(4-methoxyphenyl)propenoic acid methyl ester, or methyl trans-4-O-methyl-p-coumarate (peak 23), as well as lower amounts (nearly 5% of total peak area) of the fully methylated derivative of ferulic acid, i.e., trans-3-(3,4-dimethoxyphenyl)propenoic acid methyl ester, or methyl 4-O-methyl-ferulate (peak 29). In addition to the trans-forms of methylated p-hydroxycinnamic acids, minor amounts of the cis-isomers (peaks 17 and 26) were also identified.…”