Impact of feed injection and batch processing methods in hydrothermal liquefaction

Abstract Starch hydrothermal liquefaction (HTL) using batch and feed injection methods was studied at 300 °C and 10, 30, 60 min residence times with 2% feedstock concentration. The authors found much higher solid yield in batch mode compared to feed injection mode and that the solid yield increased linearly with feedstock injection rate. The HTL oil formation pathway was established that light water-soluble oil (ethyl acetate extracted liquid phase oil) forms first, followed by heavy water-soluble oil (dichloromethane extracted liquid phase oil), and then heavy acetone-soluble oil (dichloromethane extracted acetone wash phase oil). Solid hydrochar was formed mainly through heavy acetone-soluble oil repolymerization as the reaction residence time increased. The oil compositions and HPLC analysis of the aqueous phase indicated that at an injection rate of 20 ml/min, the reaction followed the alkaline pathway while at higher injection rates of 50 and 100 ml/min, the reaction shifted to the acidic pathway.