Thermochemical liquefaction of high-diversity grassland perennials

Abstract

The hydrothermal liquefaction of low-input high-diversity mixtures of native grassland perennials (LIHD), LIHD pretreated with dilute acid, and lignin extracted from LIHD was studied. The liquid yields were optimized using the following treatment variables: heating rate (5–140 °C/min), cooling rate (5–66 °C/min), reaction temperature (300–450 °C, corresponding to a pressure range of 10–35 MPa), residence time (1–30 min), particle sizes, and catalysts (1% and 0.1% sulfuric acid, 1% NaOH, solid superacid SO 4 2−/ZrO 2–Al 2O 3, and solid alkali CaO–ZrO 2). The liquefaction yields were found to be dependent on the final liquefaction temperature, the liquefaction time, and the heating rate. The highest liquid yield, 82.1%, was achieved within a short residence time of 1 min at 374 °C. The major compounds of the liquid products from the various LIHD fractions were identified by GC–MS. LIHD could be a good candidate for the liquefaction process with a fast heating rate.