Supporting Ex Situ Catalyst Experiments with a Gas Analyzer

Technical Research Engineer Marien Bremmer MSc with the gas analyzer (blue) in the background

Technical Research Engineer Marien Bremmer MSc with the gas analyzer (blue) in the background

The performance of the catalyst before moving into the TEM was proven in this ex-situ experiment. DENSsolutions introduces a new Gas Analyzer specifically designed to work seamlessly with the Climate in situ Gas & Heating solution. By enabling analysis of reaction products, it transforms the Climate into the only platform in the market able to combine TEM-based data with information about the kinetics of the reaction under examination.

The Experiment

Palladium nanoparticles drop casted inside a Climate MEMS-based Nano-Reactor were used for the catalyst. The Climate G+ system was used for the gas supply as it is possible to mix up to three gases with this. The system was loaded with reactive gases, oxygen and methane, and reaction products, measured carbon monoxide and carbon dioxide.

Sample temperature (top) and gas partial pressure (middle & bottom) measured as a function of time.

Figure 1. Sample temperature (top) and gas partial pressure (middle & bottom) measured as a function of time.

Catalyst Performance

To measure the catalyst performance, the gas analyzer was used first in combination with accurate temperature control. As shown in the middle graph in Figure 1, the supply of reactants was maintained at a constant level. At the same time, as shown in the top graph in Figure 1, the DENSsolutions Impulse in situ control software was used to automatically ramp up the Nano-Reactor temperature from 300 to 700 °C in 60 seconds. This resulted in a drop in the level of reactant gases and a rise in the level of reaction products as shown in the bottom graph in Figure 1. When the temperature is constant the levels stabilize.

High Activity Phase Shifting

Gas mixture composition into the Nano-Reactor (top), partial pressures of gases flowing out of the Nano-Reactor (middle) and dissipated power by the Nano-Reactor heater (bottom) as a function of time.

Figure 2. Gas mixture composition into the Nano-Reactor (top), partial pressures of gases flowing out of the Nano-Reactor (middle) and dissipated power by the Nano-Reactor heater (bottom) as a function of time.

For the next experiment in Figure 2, the palladium sample was kept at a constant temperature while the concentration of methane (CH4) was increased from 5% to 10% (top graph). Fluctuations in the level of reaction products are observed at around t = 300 seconds (middle graph). The catalyst shifts in and out of a high activity phase, which is reached at elevated temperatures.

In this high-activity phase, oscillations are observed in the partial pressure of the gas reaction products. A change of activity at the sample is also indicated by oscillations in power dissipated by the heater (bottom graph).

The level of methane is dropped in steps of 0.5% from t = 500 seconds using Impulse software. The CO2 level was measured with a gas analyzer and the influence of the first drop in concentration is clear to see - the CO2 production rate becomes unstable.

The frequency of the fluctuations increases when the concentration is dropped by another 0.5% and the third drop in concentration causes the catalyst to shift back to its normal activity phase. The fourth drop stabilizes the CO2 production.

High Time Resolution

Detailed results for partial pressure (top) and power dissipation (bottom) measurements.

Detailed results for partial pressure (top) and power dissipation (bottom) measurements

Figure 3. Detailed results for partial pressure (top) and power dissipation (bottom) measurements.

Zooming in at points A and B, Figure 3 shows the results from the gas analyzer along with those from the power dissipated by the 4-point probe temperature control system. This allows for the two measurements to be correlated. The reaction gases are in a counter phase of each other and the tops of the measured power align with their extremes. This demonstrates very high stability in temperature control as well as a very high time resolution.

Conclusions

This experiment showed that a high-accuracy gas analyzer and heating control and measurement allows ex-situ experiments to be carried out to give valuable data. This data could facilitate discoveries or could be used to prepare better in situ experiments.

Marien Bremmer who conducted the experiment commented:
“Using the Climate G+ in combination with the Gas Analyzer allows you to characterize your catalyst sample ex situ, finding the best gas and temperature conditions for your reaction, and with this data to go to the TEM to finalize your research with real in situ images and spectroscopy.”

This information has been sourced, reviewed and adapted from materials provided by DENSsolutions .

For more information on this source, please visit DENSsolutions.

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