3D-printed packed bed reactor for continuous catalytic hydrogenation of nitroaromatic compounds

• Re -based catalyst for efficient NACs hydrogenation and AAMs production is developed. • Catalyst enables high-volume processing with minimal by-products in flow mode. • Sub-nanometric Re particles enhance catalytic activity in 3D-printed PBR reactors. • Achieved 90–96 % NAC conversion rates, with diffusion limits for multi-nitro compounds. • Potential for wastewater treatment and scalable industrial applications demonstrated. Aromatic amines (AAMs) are essential compounds for producing a wide range of industrial and pharmaceutical products. However, traditional synthesis methods using nitroaromatic compounds (NACs) pose environmental and health risks due to byproduct contamination and the carcinogenic nature of NACs. In this context, this study introduces a novel catalyst containing rhenium ( Re ) active sites. While this approach does not eliminate the carcinogenic risks associated with NACs, it aims to improve process efficiency. The catalyst, synthesized within a styrene-based matrix functionalized with 1,1′-carbonyldiimidazole, combines high affinity for NACs with the catalytic prowess of Re that may be also a tool in achieving process selectivity. Characterization via XPS and HRTEM confirmed the presence of highly dispersed Re species within the polymer matrix. The catalyst demonstrated superior activity in batch hydrogenation of various NACs, achieving high conversion rates. A 3D-printed packed bed reactor (PBR) was then developed for continuous flow-mode reduction of 4-nitrophenol (4-NP), achieving significant processing capacity and highlighting its potential for scalable applications. This innovative approach not only addresses environmental concerns associated with NACs but also enhances the efficiency of AAM production, presenting a viable solution for industrial processes.