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).