Research in Catalyst Field Using XRD

We talked about how catalyst materials are characterized according to elemental composition and how particle size and shape measurements are important for catalyst packing, flow, and surface area on this page. Here, we will delve deeper to consider what happens between atoms and ions on the reactive surface of catalyst materials and the internal crystal structure of catalysts.

X-ray diffraction (XRD) is one of the most powerful analytical methods for understanding the crystal structure of materials, playing a crucial role in identifying the components of catalysts and discovering what happens to their crystal structures during operation.

Simple single-element catalysts like platinum nanoparticles are not particularly beneficial with interesting XRD techniques unless accessed using SAXS and WAXS uses available on Empyrean. You can measure particle size and verify phase and unit cell parameters at once.

Most catalysts are composed of multi-phase inorganic materials with well-defined microstructures. These should be mechanically robust and chemically stable compounds that maintain their shape and chemical properties during their production and subsequent use. From initial research projects for discovering new catalyst candidates to quality inspections of catalysts during and post-use, XRD plays a significant role. Therefore, Malvern Panalytical offers various XRD devices for measuring in different settings and workflows, from detailed research to quick, automated throughput for quality control.

Crystallography of Catalysts

Investigations of the crystal structures of these powerful crystalline materials can be conducted on Aeris and Empyrean equipment. The most common measurements are confirming changes in crystal structure, amorphous vs. crystalline ratios, and identifying the phases and compositions of multi-phase mixtures. Empyrean can also be used to investigate subtle changes in strain within crystalline unit cells. With PDF (Pair Distribution Function) analysis, advanced measurement methods like ‘total scattering’ can be used to study highly amorphous or defective structures. Due to highly sensitive detectors, total scattering profiles previously only visible at synchrotron X-ray sources can now be collected and analyzed in the lab.

Sometimes catalysts are a combination of a porous inorganic substrate with ‘loaded’ catalytic elements like noble metals. X-ray diffraction is highly sensitive to changes in the crystal lattice caused by the presence of new atoms and can be a good method for measuring the impact of loading on the integrity of crystalline substrates.

Some catalyst materials are designed to be porous within the lattice with interconnected channels to provide increased surface area to facilitate catalytic reactions. New materials like designed mesoporous substrates and MOF (Metal-Organic Framework) materials always emerge with new and exciting potential. Micro, meso, and nanopores often required in catalyst materials are highly aligned, can exist on multiple length scales, providing complex surface systems, offering far greater catalytic activities than non-porous materials. Besides XRD structural enhancements, X-ray scattering methods such as SAXS grazing incidence SAXS (GI-SAXS) and reflectivity measurements can be utilized in the Empyrean XRD system. Together they investigate porosity scaling from lattice gaps to nanopores.

Exploring Catalyst Operando

Initial research on catalytic systems often involves mechanical understanding at the atomic and molecular level. However, when applied to real scenarios, the catalytic environment can become much more complex. For example, you may need to operate catalysts under gradually changing physical and thermal conditions to reduce reactor downtime. With Empyrean, operando phase or structural analysis measurements can be performed under various simulated reactor conditions. Such laboratory studies allow understanding and charting safe temperature-pressure-chemical regimes, saving time and costs in later stages.

Crystallographers are Happy People

Overall, catalysts have much to satisfy crystallographers. New inorganic materials are already a crystallographer’s dream, but when adding porous and operando studies, the pleasures of using an X-ray diffractometer are endless.

To learn more about all our solutions for catalyst production, download the full brochure here.

Interested in MOFs? Find the MOF Solutions brochure here!