Pyrolysis of lignin in ZnCl2-based molten salts: Optimization of bio-oil yield under continuous-flow conditions and characterization of bio-products

Influence of parameters temperature, time, and nitrogen flowrate on product yields were investigated in an optimized gram-scale reactor using conventional statistical methods (i.e. ANOVA test). LignoBoost lignin was used as feedstock and typical values of yields for slow pyrolysis were obtained with zinc chloride based molten salt media. Water content in liquid phase was evaluated using Karl Fisher tritation method and best conditions for bio-oil yield were obtained. GC-MS technique and analysis as NMR were performed on collected liquid samples; most phenol-derivates (i.e. guaicol) were detected. Comparison between liquid samples and feedstock by GPC revealed the degradation effects with loss in MW average value. Quantitatively gas phase analysis using thermo conductivity detector revealed typical syngas compounds as carbon dioxide and carbon oxide; also, hydrogen presence at high temperature was observed. Solid products analysis, using conventional method (Elemental Analysis, XRD) was performed with a particular but not extensive focus on salt’s recyclability possibility in pyrolysis process testing different physical treatments. Temperature revealed its important role in pyrolysis processes as governor in parallel phenomena as gasification. For each analysis, comparison with and without molten salts revealed the gain in process whenever they were used, promising for this mixture a good media in pyrolysis’s technology