Synthesis of Malic Acid on Montmorillonite K10: A Langmuir-Hinshelwood Kinetic Study

To accelerate the reaction of hydration of fumaric acid (F) to produce malic acid (M), Montmorillonite K10 (MK10) was tested as a solid acid catalyst. The experiments were performed in a stirred pressurized batch reactor at a catalyst concentration of 4.7%-9.4% (w:w), and temperatures of 448-493 K for times up to 36000 s. The concentrations of F, M, and maleic acid (Mx) formed from a secondary isomerization reaction were determined at different reaction times by UPLC analysis. MK10 increased the final conversion of F to at least 20% without any observed decay of its catalytic activity for four cycles of use. A reliable catalytic model that assumes that the surface reactions of isomerization and hydration of F are the rate-controlling steps was suggested. External mass-transfer resistances and diffusional limitations were not important.