Abstract

Additive manufacturing of catalyst and sorbent materials promises to unlock large design freedom in the structuring of these materials, and could be used to locally tune porosity, shape and resulting parameters throughout the reactor along both the axial and transverse coordinates. This contrasts catalyst structuring by conventional methods, which yields either very dense randomly packed beds or very open cellular structures. Different 3D-printing processes for catalytic and sorbent materials exist, and the selection of an appropriate process, taking into account compatible materials, porosity and resolution, may indeed enable unbounded options for geometries. In this review, recent efforts in the field of 3D-printing of catalyst and sorbent materials are discussed. It will be argued that these efforts, whilst promising, do not yet exploit the full potential of the technology, since most studies considered small structures that are very similar to structures that can be produced through conventional methods. In addition, these studies are mostly motivated by chemical and material considerations within the printing process, without explicitly striving for process intensification. To enable value-added application of 3D-printing in the chemical process industries, three crucial requirements for increased process intensification potential will be set out: i) the production of mechanically stable structures without binders; ii) the introduction of local variations throughout the structure; and iii) the use of multiple materials within one printed structure.

Highlights

  • Catalysis is a field in chemical engineering which has made tremendous progress in the past decades

  • Direct Ink Writing (DIW) is one of the many synonyms that exist for extrusion-based methods, all of which function on the same principle, but with subtle differences (Travitzky et al, 2014)

  • Whilst the latter method did take significantly longer due to the various steps of post-processing, activation and impregnation, it is an important development for the application of the 3D-printing concept in catalysis; in the first place because impregnation of the shaped body unlocks a larger variety of catalyst holdups compared to washcoating; and secondly, because the ability to apply chemical functionality after printing allows for the production of more generic structures that can be tailored for specific reactions by impregnation

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Summary

INTRODUCTION

Catalysis is a field in chemical engineering which has made tremendous progress in the past decades. For the structuring of catalysts and sorbents this technology holds potential for providing a very high degree of design freedom, which allows for the tailoring of structures to specific operating windows and overcome the limitations of conventional shaping methods Most interesting in this regard is the spatial variations of catalyst geometry that can be created throughout the reactor. With the reviewed cases and process intensification principles in mind, the potential operating benefits of 3D-printed structures over conventional technologies can be considered Such an analysis is vital, since it should be realized that the use of additive manufacturing to produce components in bulk is not an obvious choice. It will be argued that 3D-printing of sorbent and catalyst, either as separate structures or in an integrated multi-material configuration, holds potential for key applications in the chemical process industries

CONVENTIONAL SHAPING METHODS
Granules
Pellets
Extrudates
Honeycomb Monoliths
MATURE ADDITIVE MANUFACTURING TECHNIQUES FOR CATALYST AND SORBENT MATERIALS
Direct Ink Writing
Digital Light Processing
The Reactor Scale
Logpile Structures
Washcoated and Metal Structures
POTENTIAL FOR INCREASED PROCESS INTENSIFICATION
Binderless Printing
Local Variations
Multi-Material Printing
CONCLUSION
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