EXPLOITING X-RAY DIFFRACTION TECHNIQUES FOR CATALYTIC MATERIALS CHARACTERIZATION

Structural Analysis

Catalysts have become critical materials for a wide variety of applications in our modern-day industrial world. Among the different types of techniques utilized to characterize catalytic materials, X-ray diffraction (XRD) holds a unique place in that it can be utilized to obtain both qualitative and quantitative phase information of crystalline materials as well as for the analysis of amorphous and nanomaterials. While heterogeneous catalysts are ideally suited for XRD analysis, both homogeneous and biocatalysts can also be studied via this method. In a recent white paper, Characterization of Catalytic Materials on Laboratory-Based X-Ray Diffraction Platforms, we highlight several techniques that you can perform on Malvern Panalytical’s floor-standing and compact XRD platforms to assist in the characterization of catalytic materials. Many may be familiar with X-ray powder diffraction (XRPD) for the analysis of crystalline materials (i.e. phase identification and quantification) through Bragg’s Law, as depicted in Figure 1. Malvern Panalytical’s line of X-ray diffraction instruments can provide this information for both crystalline and amorphous phases as well as providing information about crystallite size and microstrain through the examination of the peak breadths.

Figure 1 Illustration of Bragg diffraction from a crystalline material. At a specific angle (θ) the two waves scattered from atoms separated by a distance (d) will interfere constructively and a signal will be detected, (n = 1,2, 3…).

In addition, specialized XRD methods such as non-ambient (NA) measurements along with X-ray scattering techniques such as pair distribution function analysis (PDF) and small-angle X-ray scattering (SAXS), can provide a more in-depth understanding of catalytic materials. One can examine catalytic samples under relevant non-ambient conditions to explore reaction pathways, observe phase changes, and examine the material’s thermal stability. Utilizing various non-ambient stages, available on both floor standing and compact models, the temperature, humidity, and atmosphere can all be precisely controlled during measurements. Furthermore, one can obtain information about particle size and shape as well as short- and intermediate-range order through the aforementioned X-ray scattering techniques which have traditionally been relegated to synchrotron facilities. However, thanks to technologies such as our ScatterX78 stage and GaliPIX3D detector, these measurements can now be performed in-house [1,2].

Instrument Versatility

Standard powder X-ray diffraction measurements, including those under non-ambient conditions (up to 500° C), are easily performed on the Aeris compact X-ray diffractometer. This instrument has a comparable resolution, scan-times, and peak intensities to the floor standing Empyrean system. Furthermore, all of the standard PXRD measurements, as well as the aforementioned advanced techniques (NA, SAXS, and PDF), can be performed on a single Empyrean instrument with Malvern Panalytical’s PreFIX (Pre-aligned Fast Interchangeable X-ray modules) technology. This allows stages and optics to be quickly exchanged without the need for re-alignment of the instrument. Figure 2 shows an example of a component mounted on the Empyrean instrument utilizing the PreFIX technology.

Figure 2 Image of an XRD accessory (beam knife) inserted in a PreFIX block on the Empyrean instrument.

Powerful Software

Our HighScore (Plus) software can be utilized for the analysis of data from both the Empyrean and Aeris platforms. With this package, phase identification and quantification can be easily performed along with more advanced analysis techniques such as the determination of lattice parameters, peak widths, crystallite size, micro-strain, and PDF analysis [3]. Furthermore, features like cluster analysis are also included in the HighScore Plus package and can be exploited for processing large datasets such as those obtained from non-ambient measurements [4]. Lastly, Malvern Panalytical’s EasySAXS software provides a straightforward method for obtaining relevant information from data collected during SAXS experiments. These include the volume-weighted size distribution, particle shape, and specific surface area [5]. Figure 3 shows examples of analysis performed in the two packages.

Figure 3 Analysis performed in the HighScore (Plus) software package: A.) Phase identification and quantification, B.) Cluster analysis, C.) PDF analysis. Additionally, an example of the EasySAXS user interface (D.) is shown.

True power comes from combining data

No doubt, X-ray diffraction techniques can provide a more in-depth understanding of catalytic materials. Our white paper highlights several techniques that can be performed on Malvern Panalytical’s floor standing and benchtop XRD platforms to assist in their characterization.

 

Written by: Brad Losey, posted by: Malvern Panalytical (www.materials-talks.com)

 

References

  1. Te Nijenhuis, J., Gateshki, M., & Fransen, M. J. (2009). Possibilities and limitations of x-ray diffraction using high-energy x-rays on a laboratory system. Zeitschrift Für Kristallographie Supplements, 2009(30), 163-169. doi:10.1524/zksu.2009.0023
  2. Confalonieri, G., Dapiaggi, M., Sommariva, M., Gateshki, M., Fitch, A. N., & Bernasconi, A. (2015). Comparison of total scattering data from various sources: The case of a nanometric spinel. Powder Diffraction, 30(S1), S65. doi:10.1017/s0885715614001389
  3. Degen, T., Sadki, M., Bron, E., König, U., & Nénert, G. (2014). The HighScore suite. Powder Diffraction, 29(S2). , S13-S18. doi:10.1017/s0885715614000840
  4. Automatic analysis of large amounts of X-ray diffraction data with HighScore Plus. Malvern Panalytical application data sheet.
  5. Bolze, J.; Kogan, V.; Beckers, D.; Fransen, M. High-performance small- and wide-angle X-ray scattering (SAXS/WAXS) experiments on a multi-functional laboratory goniometer platform with easily exchangeable X-ray modules. Review of Scientific Instruments2018, 89(8), 085115.Bolze, J., Kogan, V., Beckers, D., & Fransen, M. (2018). High-performance small- and wide-angle X-ray Scattering (SAXS/WAXS) experiments on a MULTI-FUNCTIONAL laboratory Goniometer platform with easily EXCHANGEABLE x-ray modules. Review of Scientific Instruments, 89(8), 085115. doi:10.1063/1.5041949

 

IAGeo SDAR Reference Materials

 NIST soil samples have long been the go-to solution for analysts looking for standards of varying levels of contaminants when testing sediment and soil samples for contamination. IAG has developed a solution to the higher priced NIST CRMS in the form of three RM materials which closely match the composition of each of the popular NIST Soils 2709, 2710 and 2711.

SDAR Samples

The SdAR series of reference materials have been designed to resemble the sediments, soils and related materials which are typically sampled when monitoring levels of environmental contamination. This contamination  is often associated with, discharges from mining operations or industrial pollution. The preparation of these materials was carefully considered, and was done to maintain the properties which make a natural sample so desirable. Each sample is a carefully prepared combination of ore-grade material from multiple locations, diluted with baseline soils and sediment. The use of natural materials maintains the effect of mineralogy on chemical analysis, and the use of distinct blending ratios provides a smooth and gradual calibration over a wide concentration range.

Each of these three standards are available in polycarbonate bottles containing 80g of material.

This unique series of reference materials have been designed as substitutes for the expensive NIST 2709-2711 metal-bearing sediment SRMs of similar composition (see diagrams). A low (SdAR-L2), medium (SdAR-M2) and high (SdAR-H1). These reference materials are intended for use in the calibration of portable XRF instruments and in routine laboratory analysis.

SdAR-H1-vs-SRM-2710a  SdAR-M2-vs-SSRM-2711a

New analysis has been conducted on these materials to include data based on aqua-regia selective extraction procedures, which is now available in an addendum to the original certificates. This information will be particularly useful for laboratories seeking reference materials for aqua-regia  extractions performed at 90 to 110°C, reflecting the procedures commonly used by commercial laboratories which service the industries for mining and geochemical exploration, and for environmental monitoring.

These standards are available individually or as a set with special set pricing.

To see the full data-set for all standards, including the aqua-regia extraction, download the certificate

SdAR Soils Cert

Posted by: ARMI MBH on https://www.armi.com/sdar-reference-set