Levulinic acid production based on extrusion and pressurized batch reaction

Abstract

Levulinic acid is a highly versatile chemical with numerous industrial uses, having the potential to become a commodity chemical. It can be used as a raw material for resins, plasticizers, textiles, animal feed, coatings and antifreeze. Starches and sugars are typically converted to levulinic acid using a batch reactor. Blends of corn starch (70%), sulfuric acid (5%), and water (25%) were extruded using a laboratory-scale, twin-screw extruder equipped with a static mixer and a condenser. The extrudates were further reacted, under pressure, with additional water and sulfuric acid. For any given set of reaction conditions, the levulinic acid yields in high amylose corn starch (HAS) samples were about 3% higher than those in normal corn starch (NS) samples. The levulinic acid yield increased as reaction time increased from 20 to 60 min. However, the yields in the samples containing 25% (w.b.) extruded starch and further reacted at 40 and 60 min of reaction time were not significantly different. The levulinic acid yield increased as the sulfuric acid content of the secondary treatment was increased from 2 to 4%. A sulfuric acid content greater than 0.3% by weight of starch did not increase levulinic acid yield. The levulinic acid yield increased from 7 to 47% as reaction temperature increased from 160 to 200 °C under pressure, whereas the glucose yield decreased from 77 to 0%. The levulinic acid yields from the extruded samples were higher than those from unextruded starch samples. The difference increased from 0.4 to 11.3% as reaction temperature increased from 160 to 200 °C. The maximum yields of glucose, hydroxymethyl furfural (HMF), and levulinic acid were obtained at 160, 180, and 200 °C reaction temperatures, respectively. Glucose and levulinic acid yields increased as extrusion temperature increased and screw speed decreased. The maximum yield of levulinic acid was 47.5% when extruded HAS was reacted at 200 °C after being extruded at 180 °C and 20 rpm screw speed.