Optimization of levulinic acid conversion into methyl levulinate via methyl esterification catalyzed with aluminum sulfate

The use of low-cost, widely available environmental friendly catalysts may strengthen the sustainability of lignocellulosic biomass conversion into levulinic esters. In this respect, the present study aimed to optimize the methyl esterification reaction between levulinic acid (LVA) and aluminum sulfate [Al 2 (SO 4 ) 3 ] with a view to producing methyl levulinate (MLV). The Box–Behnken design for three factors was applied to investigate the influence of reaction time (60, 120, and 180 min), alcohol:acid molar ratio (4:1, 8:1, and 12:1), and catalyst concentration (0.02, 0.04, and 0.06 mol L −1 ) on LVA conversion into MLV. The reactions occurred in a Parr Instruments stainless steel reactor, at a temperature of 140 ºC and 733 rpm rotation. The results indicated that the interaction between molar ratio and catalyst concentration has a significant influence on LVA conversion. The regression model obtained is significant and predictive, with an R 2 value of 0.86. Analyses of response surfaces showed that a 60 min reaction time produces high conversion, irrespective of the amount of catalyst. Fixing the shortest reaction time and lowest Al 2 (SO 4 ) 3 concentration, the molar ratio indicated for the reaction would be 1:6. The levels selected provide conversions varying from 86.83% to 99.27%, demonstrating the efficiency of a low-cost catalyst at low concentrations.