Pyrolysis of kraft lignin in molten ZNCL2-KCL media with tetralin vapor addition

Kraft lignin was pyrolyzed in molten salt media of ZnCl₂-KCl mixture with tetralin vapor added in 0.4 and 4 mol% diluted with N₂ in the temperature range of 400 to 700°C. The gas chromatographic analyses of pyrolysis products revealed that the yield of H₂ was not increased by tetralin vapor addition. This fact implies that the hydrogen radical produced from tetralin is consumed in the formation of phenolic compounds and light liquids but not in the formation of H₂. p-Cresol was the most abundant phenolic compound. The yield of total phenolic compounds with 4 mol% tetralin vapor added was increased by ca. 80% as compared to that in neat pyrolysis of Kraft lignin.     

Pyrolysis of kraft lignin in the presence of molten ZnCl2-KCl mixture

Pyrolysis of kraft lignin was carried out using small reactors with an added ZnCl₂-KCl mixture at three levels of temperature, 500°C, 550°C and 600°C, and three levels of salt-to-lignin ratio (SR), 1, 2 and 3. Nineteen kinds of phenolic compound were identified and their quantitative determinations were made by gas chromatography. The yield of gaseous products determined gravimetrically exhibited a strong dependence on the added amount of salt mixture, and its lowest value was obtained at SR of 1. The formation of gaseous products, apparently stemming from decomposition of liquid products and tar, was observed at reaction times longer than 30 min. At SR of 1 and a temperature of 550°C, all phenolic compounds attained their maximum yields almost synchronously at a reaction time of 15 min. Cresol's formation was slightly increased with the amount of added salt mixture. At a temperature of 550°C, cresols and guaiacols decomposed according to a pseudo-first-order lumping model, while catechols did not follow the similar model.