Process intensification of 2-amylanthraquinone hydrogenation in a micro-packed-bed reactor for H2O2 synthesis†

In the synthesis of hydrogen peroxide, the hydrogenation reaction in the Riedl–Pfleiderer process faces operational risks and inefficiency challenges. This work pioneers the application of micro-packed-bed reactors (μPBRs) in 2-amylanthraquinone (AAQ) hydrogenation, establishing a transformative strategy for enhancing the Riedl–Pfleiderer process. By utilizing microscale effects, we achieved a record space–time yield of 336.8 g_H2O2 g_Pd⁻¹ h⁻¹ — 25× and 21× higher than those of conventional slurry reactors and trickle-bed reactors, respectively. For the first time, AAQ demonstrated superior performance over 2-ethylanthraquinone (EAQ) in μPBRs, addressing the critical challenge of balancing hydrogenation efficiency (10.13 g L⁻¹) with 99.9% effective anthraquinone retention, which could not be achieved in prior systems. Additionally, systematic optimization of solvent composition (3 : 1 TMB/TOP), reaction parameters (50 °C, 300 kPa), and catalyst utilization revealed μPBRs' intrinsic advantages: ultra-short apparent residence time (9 s), minimized over-hydrogenation risk, and exceptional stability (99.1% effective anthraquinone retention after 10 cycles). Furthermore, a validated mass transfer model (prediction error <20%) was established for understanding the intrinsic mechanisms within gas–liquid–solid interactions, offering a predictive tool for reactor design. This study provides a safety-enhanced paradigm for H₂O₂ synthesis, overcoming long-standing limitations in industrial process intensification.