497 / 2018-09-10 08:15:29

Pyrolysis Characteristics of Lignin Extracted from Willow by Deep Eutectic Solvents (DESs)

全体主题 > 生物质液体燃料

Lignin extracted by deep eutectic solvent (DES) treatments has been reported to have high yield, high purity, and low molecular weight, which would be of benefit for future valorization. As the domain of aromatic nuclei found in nature, lignin has great potential to be converted into aromatic chemicals or biofuels through thermochemical depolymerization. In the present examination, the pyrolysis characteristics of DES-lignin samples (D6h, D12h, D18h, D24h), i.e., lignin extracted from willow (Salix matsudana cv. Zhuliu) by DES (1:10 molar ratio of choline chloride and lactic acid) treatment at 120 °C for 6 h, 12 h, 18 h, 24 h, were investigated with the techniques of TG, Py-GC/MS, and in-situ diffuse reflectance infrared pyrolysis (in-situ-FTIR). The thermal behaviours and the evolution profiles from each sample pyrolysis were compared and discussed in depth focusing on reveal the relationship between the structure of DES-lignin and the properties of pyrolysis product. The results showed little difference in thermogravimetric properties and the types of pyrolysis products of DES-lignin isolated with different extraction times. The thermal degradation of DES-lignin mainly occurred at 300-600 ºC with significant cleavage of side chain chemical bonds in lignin molecules, and the residue char yield was about 40% when elevated to 800 ºC. The pyrolysis products contained various types of alkylated and/or oxyalkylated phenolic compounds, among which the G- and S-type phenols (derived from Guaiacyl and Syringyl units) reached the maximum yield of 47.1% and 32.4% at 450 and 550 ºC, respectively. In addition, product distribution was remarkably affected by pyrolysis temperature as well as the DES treatment time used for isolate lignin.