Multiscale Mechanistic Insights of Shaped Catalyst Body Formulations and Their Impact on Catalytic Properties

Abstract

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.

A Facile Strategy to Prepare Shaped ZSM-5 Catalysts with Enhanced Para-Xylene Selectivity and Stability for Toluene Methylation: The Effect of In Situ Modification by Attapulgite

“…Calculated from the saturation adsorption amounts, the n-hexane to cyclohexane adsorption ratio of HZ-bo increased from 1.8 to 1.9 after regeneration, whereas that of HZ-atp decreased from 1.9 to 1.7 after regeneration. It means that the initial para-selectivity increment for regenerated Z5-bo was not only due to the reduced acidity but partially due to the more restricted pore openings, which might be caused by the aluminum species migration in alumina-bound ZSM-5 extrudates [20,31,36]. In the HZ-atp case, the extent of pore openings reduction decreased after regeneration, which indicated that the in-situ modification of acidity was the main reason for the increase of para-selectivity over HZ-atp.…”

Influence of Nanoscale Intimacy and Zeolite Micropore Size on the Performance of Bifunctional Catalysts forn-Heptane Hydroisomerization

“…Acetic acid was added as a peptizing agent for the boehmite particles, to aid in mixing and adhesion with the zeolite particles. 52 The mixture was dried overnight at 120 °C in static air followed by calcination at 550 °C for 2 h with a ramp of 5 °C min –1 . Afterward, the product was crushed and sieved to obtain grains of 212–500 μm diameter.…”

Effect of Mesoporosity, Acidity and Crystal Size of Zeolite ZSM‐5 on Catalytic Performance during the Ex‐situ Catalytic Fast Pyrolysis of Biomass

“…For zeolitic materials, which have poor self‐binding properties, the inclusion of binders ‐ typically, alumina, silica or clays [16–17] ‐ is needed to attain durable catalyst bodies with the required strength and attrition resistance [18] . Yet, the selection of the specific binder or other additives, as well as the proportions used are of crucial importance, as they induce important modifications in the overall properties of the catalyst material and thus in activity [15,19–20] . Some examples of technical zeolite ZSM‐5 based catalysts extruded with clay minerals as binders can be found in the literature.…”