Progress in catalysis has been, is, and will always be motivated by societal needs (e.g. environment, energy, chemicals, fuels), with the ultimate aim of improving process efficiency on a technical scale. Technical catalysts are often complex multicomponent millimetre-sized bodies consisting of active phases, supports, and numerous additives in shaped forms suitable for their commercial application. They can differ strongly in composition, structure, porosity, and performance from research catalysts, i.e. laboratory-developed materials constituted by a single bulk or supported active phase in powder form, which are the predominant focus of academic investigations. The industrial manufacture of heterogeneous catalysts, encompassing the upscaled preparation, formulation, and structuring, is encircled by secrecy and is decisive for the overall process viability. Yet despite the tremendous relevance, understanding the added complexity of these multicomponent systems and the consequences for the respective structure-property-function relationships has been largely neglected. Accordingly, our review examines the intricacies of the scale up of heterogeneous catalysts. While emphasising the lack of fundamental knowledge we point out the multiple functions that additives could provide by enhancing the mass and heat transfer properties, acting as co-catalysts, or imparting improved chemical, mechanical, or thermal stability. Recent exemplary studies developing rational approaches to prepare, characterise, and evaluate technical catalysts are analysed in detail and new directions for research in this field are put forward.

A major challenge in the implementation of laboratory-designed catalysts is the scale-up into technically relevant forms. Advanced characterization is essential to understand and optimize catalyst assembly and function in industrial reactors. This Article presents an integrated approach to visualizing millimetre-sized extrudates and granules of a hierarchical MFI-type zeolite, displaying trimodal networks of micropores (0.56 nm), intracrystalline mesopores (∼10 nm) and macropores (∼200-300 nm). As exemplified for the conversion of methanol to olefins, the hierarchical zeolite yields a superior performance compared to its conventional analogue. The combination of dedicated specimen preparation with state-of-the-art optical, X-ray and electron-based microscopic and tomographic techniques proves a powerful methodology to reveal otherwise inaccessible information regarding structural organization over the whole range of length scales. It is expected that these tools will play a crucial role in the rationalization of scale-up principles in catalyst development.

The scale-up of zeolite catalysts from powder to industrially relevant shapes is widely neglected in fundamental research because of the added preparative and analytical complexity. Binders incorporated to improve mechanical stability and related structuring steps can cause decisive performance alterations, which are currently difficult to predict. Here, by characterizing physical, extruded, and milled admixtures of MFI zeolites with common silica, alumina, or clay binders, we elucidate the cause and magnitude of property variations induced by shaping. Subsequent evaluation in the conversion of methanol to hydrocarbons confirms the corresponding catalytic impacts. Our findings show that binder effects can, without optimization, match or even exceed those of hierarchically structuring the porosity of the MFI crystals. The macroporosity and related mass transfer properties of the technical bodies are enhanced on extrusion with attapulgite and kaolin as a result of their larger particle size. Comparatively, the acid site density and speciation is binderdependent. Although a decreased Brønsted acidity, due to the partial dealumination or ion exchange of the zeolite framework, reduces the intrinsic activity of the catalysts, no direct correlation is observed with the selectivity or catalyst lifetime. The unique role of attapulgite in promoting the longevity and light-olefin selectivity of the zeolite is correlated with the reversible neutralization of the framework by mobile Mg species. Ball-milling proves a complementary tool to rapidly screen for potential reactions between component phases with small sample quantities. An improved understanding of the complex morphological and chemical interactions within zeolite−binder composites and of how they can be effectively tuned will ultimately accelerate the development of superior catalytic technologies.