What are the best techniques for characterizing catalysts?

1 Activity and conversion

One of the simplest and most important ways to characterize a catalyst is to measure its activity and conversion. Activity is the rate of reaction per unit mass or surface area of the catalyst, while conversion is the fraction of reactants that are transformed into products. You can determine these parameters by conducting a kinetic experiment, where you vary the temperature, pressure, and concentration of the reactants and products, and monitor the changes in the reaction rate. By plotting the data, you can calculate the activation energy, the frequency factor, and the reaction order of the catalyst.

2 Selectivity and yield

Another way to characterize a catalyst is to measure its selectivity and yield. Selectivity is the ratio of the desired product to the total products formed, while yield is the ratio of the desired product to the reactants consumed. These parameters reflect the ability of the catalyst to direct the reaction towards a specific outcome, avoiding unwanted by-products or side reactions. You can measure selectivity and yield by analyzing the composition of the product stream, using techniques such as gas chromatography, mass spectrometry, or infrared spectroscopy.

3 Surface area and porosity

A third way to characterize a catalyst is to measure its surface area and porosity. Surface area is the total area of the exposed surface of the catalyst particles, while porosity is the fraction of the volume of the catalyst that is occupied by pores. These parameters affect the availability and accessibility of the active sites on the catalyst, where the reaction occurs. You can measure surface area and porosity by using techniques such as adsorption isotherms, mercury porosimetry, or nitrogen physisorption.

4 Structure and morphology

A fourth way to characterize a catalyst is to measure its structure and morphology. Structure is the arrangement of atoms and molecules in the catalyst, while morphology is the shape and size of the catalyst particles. These parameters influence the electronic and chemical properties of the catalyst, such as its reactivity, stability, and dispersion. You can measure structure and morphology by using techniques such as X-ray diffraction, scanning electron microscopy, or transmission electron microscopy.

5 Spectroscopy and microscopy

A fifth way to characterize a catalyst is to use spectroscopy and microscopy techniques. These techniques can provide detailed information about the nature, location, and interaction of the active sites, the adsorbed species, and the reaction intermediates on the catalyst surface. They can also reveal the changes in the catalyst during the reaction, such as sintering, poisoning, or coking. Some examples of spectroscopy and microscopy techniques are Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance, and atomic force microscopy.

6 Modeling and simulation

A sixth way to characterize a catalyst is to use modeling and simulation techniques. These techniques can help you understand the underlying mechanisms and dynamics of the catalytic reaction, such as the reaction pathways, the rate-determining steps, the energy barriers, and the reaction kinetics. They can also help you design and optimize new catalysts, by predicting their performance, stability, and selectivity. Some examples of modeling and simulation techniques are density functional theory, molecular dynamics, kinetic Monte Carlo, and computational fluid dynamics.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?