Home > Services > Catalyst Evaluation
 

Catalyst Evaluation

Catalyst performance can be evaluated during and after installation to ensure compliance with all environmental regulations over the lifetime of the catalyst.

Catalyst activity is evaluated by Johnson Matthey’s synthetic catalyst activity test (SCAT) while potential causes of deactivation can be investigated using several analytical techniques. The appropriate tests are tailored to the specific application and operating conditions. Test results are used to advise the customer of the appropriate course of action.

Evaluating catalyst performance in the laboratory.

Evaluating catalyst performance
in the laboratory.

Activity Test

Johnson Matthey’s SCAT involves measuring the activity of a catalyst sample under controlled conditions. The test reactor allows complete control of flow rate, temperature and gas composition which can include NOx, CO, hydrocarbons and SO2. Based on accumulated experience with characteristic performance profiles under standard conditions, it is often possible to predict the performance of the catalyst in the field from the SCAT data.

X-Ray Fluorescence

X-ray fluorescence (XRF) is used to semi-quantitatively identify contaminants in catalyst samples. XRF results can be used to identify elements such as phosphorus, silicon and sulfur which can poison a catalyst and result in deactivation.

BET Surface Area Analysis

The BET surface area analysis uses adsorption of nitrogen at liquid nitrogen temperatures to measure the total surface area of the catalyst sample. Loss of surface area and porosity is indicative of sintering which occurs upon exposure to excessive temperatures and results in catalyst deactivation.

Pore Structure Analysis

The porous structure of the catalyst allows diffusion of the reactants into the catalyst and access to the active sites. Blockage of the pores can result from accumulation of contaminants and destruction of the pore system can result from exposure to excessive temperatures. Both will impede the gas transport and diminish the overall activity of the catalyst.

Three characteristics are measured:

  • Pore volume [mm³/g] and
  • Average pore radius [Å] by Hg intrusion method
  • Total porosity [%]
Optical and SEM micrographs of catalyst coated on ceramic substrate

Optical and SEM micrographs
of catalyst coated on ceramic substrate
Optical and SEM micrographs of catalyst coated on ceramic substrate

Optical and SEM micrographs
of catalyst coated on ceramic substrate

X-ray diffraction (XRD) can identify physical changes in the catalytic materials such as sintering and crystalline phase changes that are characteristic of exposure to excessive temperatures.

Thermogravimetric analysis (TGA) is an analytical technique in which changes in composition or physical properties of the catalytic material are measured as a function of temperature. It is especially useful in identifying coking by measuring CO2 that evolves as the sample is heated.

Scanning electron microscopy/energy dispersive x-ray (SEM/EDX): SEM is used to generate high resolution images of catalysts by targeting the catalyst surface with an electron beam and detecting the backscattered electrons. SEM images can reveal characteristics and structural defects too small to be detected with optical microscopy. SEM is often used in tandem with EDX which provides quantitative elemental composition.