Development of a kinetic model of ethylene methoxycarbonylation with homogeneous Pd catalyst using a capillary microreactor

- Kinetics of ethylene methoxycarbonylation were studied in a capillary reactor.
- The methanolysis of the Pd-hydride cycle was the rate limiting step.
- A ranking of experiments approach improved kinetic parameter estimability.

The kinetics of gas-liquid methoxycarbonylation of ethylene using 0.0013 mol/L Pd(dtbpx)(dba) homogeneous catalyst at 100 °C and 10 bar were studied in a continuous flow Hastelloy capillary microreactor of 1 mm internal diameter. Characterisation of the hydrodynamics was conducted to confirm plug flow behaviour and evaluate liquid volume fraction, both important for reactor modelling. Reaction experiments were carried out to investigate the effect of ethylene, methanol and carbon monoxide concentrations on the observed reaction rate. Vapour-liquid equilibrium was employed to calculate component concentrations at the inlet and outlet reactor conditions from the experimental data. In conjunction with a reactor model, the results were used to evaluate kinetic models based on the Pd-hydride catalytic cycle. A kinetic model considering methanolysis as the rate limiting step agreed with the experimental data. A model-based design of experiments strategy was applied for selecting the most informative experiments to achieve a precise estimation of the kinetic model parameters.

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