An Integrated Two-Stage Strategy for Efficient Lactic Acid Production via Ionic Liquid-Assisted Mechanochemical Pretreatment and Catalytic Conversion

Efficient conversion of cellulose to value-added lactic acid remains challenging because the rigid crystalline structure of cellulose limits its accessibility and subsequent conversion. This study developed an integrated strategy combining ionic liquid-assisted ball milling with catalytic lactic acid production. Ionic liquid type, ball-milling time, ionic liquid concentration, and glucose addition were examined during cellulose pretreatment. Among the ionic liquids tested, 1-butyl-3-methylimidazolium acetate ([Bmim][OAc]) provided the highest apparent water-soluble fraction. After 60 min of ball milling with 0.17 M [Bmim][OAc], the apparent water-soluble fraction increased from 5.1% for untreated cellulose to 63.7%, while the crystallinity index decreased from 78.1% to 44.0%. The catalytic stage was then evaluated using D-glucose as a model substrate with rehydrated hydrotalcite (r-HT) in a Ba(OH)2 medium. The r-HT/Ba(OH)2 system achieved the highest lactic acid yield of 43.6 C-% at 100 °C for 2 h, compared with 9.1 C-% for r-HT and 38.2 C-% for Ba(OH)2 alone. These results demonstrate the potential of this integrated strategy to improve cellulose accessibility while enhancing lactic acid formation from glucose, providing a basis for further development of cellulose-to-lactic-acid conversion pathways.