Intensification of carboxylic acid esterification using a solid catalyst in a mesoscale oscillatory baffled reactor platform

- Clear steady states were obtained at all conditions for the multi-steady states.
- Dynamic screening required 16% less time to run compared to the multi-steady states.
- Least process development time was obtained for multi-dimensional screening.
- Multi-dimensional approach required 30% less resources than multi-steady states.
- Amberlyst™ 70 entirely regained its catalytic activity after water spiking.

Intensified production of carboxylic acid esters has been investigated using a mesoscale oscillatory baffled reactor (meso-OBR), operated in continuous multi-steady states, dynamic and multi-dimensional modes. This study was performed to investigate the suitability of the reactor for solid-liquid reactions, capacity for quality steady states and rapid process development. A heterogeneously catalysed hexanoic acid esterification with methanol was studied in a meso-OBR packed with Amberlyst™ 70 resin as an acid catalyst. The esterification conditions investigated were feed molar ratios in the range of 1.5:1-30:1 and residence times in the range of 1 min-20 min. The meso-OBR was operated at oscillatory conditions of 4.5 Hz frequency and 8 mm amplitude (centre-to-peak) and reaction temperature of 60 °C. Clear steady states were achieved at all the residence times used, with maximum hexanoic acid to methyl hexanoate conversion of 95.4 ± 1.0% obtained at 20 min residence time and 30:1 methanol to acid molar ratio. Methyl ester conversions were 98.5 ± 1.5% at 20 min residence time and 30:1 methanol to acid molar ratio for dynamic screening, and 98.2 ± 1.1% at 14 min residence time and 21:1 methanol to acid molar ratio for the multi-dimensional mode. Use of dynamic screening required 16% less time and reactant compared to the multi-steady states approach. A more significant reduction in the process development time and reactants requirement, approximately 30% compared to the multi-steady states approach, was achieved using the multi-dimensional approach. This demonstrates a substantial reduction in process development time, another major advantage of the meso-OBR platform as the choice reactor in process development for multiphase reactions. The Amberlyst™ 70 entirely regained its catalytic activity after water spiking, and was not permanently deactivated by water.