Zeolite-based catalysts are globally
employed in many industrial
processes, such as in crude-oil refining and in the production of
bulk chemicals. However, to be implemented in industrial reactors
efficiently, zeolite powders are required to be shaped in catalyst
bodies. Scale-up of zeolite catalysts into such forms comes with side
effects to its overall physicochemical properties and to those of
its constituting components. Although fundamental research into “technical”
solid catalysts is scarce, binder effects have been reported to significantly
impact their catalytic properties and lifetime. Given the large number
of additional (in)organic components added in the formulation, it
is somehow surprising to see that there is a distinct lack of research
into the unintentional impact organic additives can have on the properties
of the zeolite and the catalyst bodies in general. Here, we systematically
prepared a series of alumina-bound zeolite ZSM-5-based catalyst bodies,
with organic additives such as peptizing, plasticizing, and lubricating
agents, to rationalize their impacts on the physicochemical properties
of the shaped catalyst bodies. By utilizing a carefully selected arsenal
of bulk and high-spatial resolution multiscale characterization techniques,
as well as specifically sized bioinspired fluorescent nanoprobes to
study pore accessibility, we clearly show that, although the organic
additives achieve their primary function of a mechanically robust
material, uncontrolled processes are taking place in parallel. We
reveal that the extrusion process can lead to zeolite dealumination
(from acid peptizing treatment, and localized steaming upon calcination);
meso- and macropore structural rearrangement (via burning-out of organic
plasticizing and lubricating agents upon calcination); and abating
of known alumina binder effects (via scavenging of Al species via
chelating lubricating agents), which significantly impact catalytic
performance. Understanding the mechanisms behind such effects in industrial-grade
catalyst formulations can lead to enhanced design of these important
materials, which can improve process efficiency in a vast range of
industrial catalytic reactions.
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