Hydrolysis of Dimethyl Methylphosphonate (DMMP) in Hot-Compressed Water

Dimethyl methylphosphonate (DMMP)
is often used as a chemical surrogate
for organophosphate nerve agents, as it exhibits similar physiochemical
properties while having significantly lower toxicity. Continuous hydrolysis
of DMMP in hot-compressed water is performed at temperatures from
200 to 300 °C, pressures of 20 and 30 MPa, and residence times
from 30 to 80 s to evaluate the effects of pressure and temperature
on reaction kinetics. DMMP hydrolysis is observed to follow pseudo-first-order
reaction behavior, producing methylphosphonic acid and methanol as
the only detectable reaction products. This is significant for the
practical implementation of a continuous hydrothermal reactor for
chemical warfare agent neutralization, as the process only yields
stable, less-toxic compounds. Pressure has no discernible effect on
the hydrolysis rate in compressed liquid water. Pseudo-first-order
Arrhenius parameters are determined, with an activation energy of
90.17 ± 5.68 kJ/mol and a pre-exponential factor of 107.51±0.58 s–1.