Maximizing Pd/C Hydrogenation Performance with Continuous Flow CSTR Cascades at Ambient Pressure

Abstract This study demonstrates the efficient implementation of heterogeneous gas–liquid–solid hydrogenation at ambient pressure using a continuous-flow reactor composed of a vertical cascade of ten continuously stirred tank reactors (CSTRs). The system enables simple operation by continuously feeding a suspended catalyst slurry alongside hydrogen gas,without the need for complex catalyst immobilization. Active agitation throughout the cascade ensures homogeneous and vigorous mixing, which in turn facilitates rapid hydrogenation even under ambient pressure conditions. Under optimized conditions, the system achieved 80% conversion of ethyl cinnamate within 4.7 min of residence time and exhibited apparent gas–liquid mass transfer coefficients (kLa) in the range of 1000–5000 h–1,comparable to those reported for advanced microreactors. Moreover, the relatively large reactor volume enabled superior productivity compared to the microstructured reactors under ambient pressure. The results demonstrate the applicability of the reactor to continuous hydrogenation, with efficient mass transfer, simple operation, and compatibility with slurry-based catalytic processes.