Acid-Catalyzed Direct Synthesis of Methyl Levulinate from Paper Sludge in Methanol Medium

Abstract

A direct synthesis of methyl levulinate from the degradation of paper sludge in a methanol medium at moderate temperatures (≤ 230 °C) was performed using low-concentration sulfuric acid (≤ 0.05 mol/L) as the catalyst. Response surface methodology with a four-factor, five-level central composite rotatable design was employed to optimize the process conditions for maximized methyl levulinate production under the condition of controlling the dehydration of methanol to dimethyl ether. The yields of methyl levulinate and dimethyl ether as a function of the process variables were fitted to second-order polynomial models through application of multiple regression analyses. A good agreement between the experimental and modeled data was obtained. When the controlled yield of dimethyl ether was less than 20%, a maximum methyl levulinate yield of 54.8% was achieved, corresponding to 27.7% (w/w) overall yield for dry paper sludge. The findings indicated that paper sludge can act as a potential biomass material for upgrading and converting into high value-added chemicals.