High-Pressure Acid-Catalyzed Isomerization and Hydration of Fumaric Acid in a Homogeneous Nonisothermal Batch Reactor

A set of chemical kinetic and phase-transition experiments was performed to investigate the competing conversions of fumaric acid into maleic and malic acids by isomerization and hydration, respectively. The reactions were carried out in sealed stainless steel batch reactors operated up to ∼1600 kPa and jacketed with glycerol at 398, 423, 448, and 473 K. The catalyst used was 0.97 M hydrochloric acid. To avoid excessive data near equilibrium, the reaction time was reduced from 720000 to 12600 s as the temperature of the heating fluid was increased. To ensure a homogeneous reaction, the solubility of fumaric acid in water was determined in the temperature range from 293 to 473 K using a high-pressure variable-volume sapphire view cell. The variation in the species concentration with time was determined by HPLC analysis of 12 reaction mixture samples per reaction run conducted twice under identical conditions. The parameters of the Arrhenius equation for the isomerization and hydration reactions were tuned on the kinetic experimental data by applying the Simplex method of optimization (k 20 = 1.27 × 10–7 s–1, k 30 = 1.29 × 107 s–1, E a2/R = −2815 K, E a3/R = 11260 K).