Industrial Catalyst Impregnation: Modern Equipment, Techniques, and Scaling Challenges

Impregnation remains the dominant manufacturing route for supported metal catalysts because it combines formulation flexibility, scalability, and comparatively low capital requirements. However, its apparent simplicity hides persistent challenges, most notably nonuniform metal distributions, sensitivity to solution chemistry and drying conditions, and limited reproducibility when transferring protocols from laboratory practice to industrial equipment. This review consolidates recent advances in impregnation science and technology, with a dedicated focus on both techniques and hardware. The governing fundamentals of wetting, capillary penetration, intraparticle transport, precursor speciation, and evaporation-driven redistribution are first revisited, emphasizing how these coupled phenomena set radial/axial metal profiles and dispersion. Conventional approaches (incipient wetness, wet impregnation, co- and sequential impregnation, and deposition–precipitation) are then benchmarked against emerging strategies, including strong electrostatic adsorption, charge-enhanced dry impregnation, engineered gradient formation, and hybrid coating/deposition concepts. An equipment-centered perspective follows, comparing rotating drums, pan coaters, high-intensity mixers, and fluidized-bed coaters across scales, and mapping critical process parameters (CPPs) to critical quality attributes (CQAs) within a manufacturing-oriented CPP→CQA framework. Industrial case studies illustrate how profile control and drying trajectories translate into measurable performance differences, while the sustainability section highlights solvent minimization, solvent/metal recovery loops, nitrate burden reduction, and process analytical technologies (PAT) as levers to reduce waste and improve safety. Finally, the main academia–industry gaps are identified and research directions are proposed to enable robust scale-up, including regime-aware multiphysics modeling, in situ/time-resolved characterization during drying/calcination, and data-driven control strategies for reproducible catalyst manufacture.