Automated Catalyst Characterization System - A catalyst characterization laboratory enclosed in one cabinet.

The AutoChem II 2920 is a fully automated chemisorption analyzer that can provide your laboratory with the ability to conduct a comprehensive array of highly precise studies of chemical adsorption and temperature-programmed reactions.

With this single instrument, you can acquire valuable information about the physical properties of your catalyst, catalyst support, or other materials. It can determine catalytic properties such as percent of metal dispersion, active metal surface area, acid strength, surface acidity, distribution of strength of active sites, BET surface area, and more.

The AutoChem II 2920 performs pulse chemisorption, temperature-programmed reduction (TPR), desorption (TPD), oxidation (TPO), and reaction analyses and does it automatically.

Wide Variety of Features and Benefits:

Chemical adsorption (chemisorption) analyses can provide much of the information needed to evaluate catalyst materials in the design and production phases, as well as after a period of use. The chemical adsorption isotherm reveals information about the active surface of a material have emerged as an indispensable companion to chemisorption isotherm analyses in many areas of industry.

• Four internal temperature-controlled zones can be heated independently up to 150 °C. This prevents condensation in the flow path and allows studies to be performed with vapors.
  
• Low internal plumbing volume assures high resolution, fast detector response, and reduces error.
  
• Highly sensitive linear thermal conductivity detector (TCD) assures the calibration volume remains constant over the full range of peak amplitudes so the area under the peak is directly proportional to the volume of gas reacted.
  
• Four high-precision mass flow controllers provide extremely accurate, programmable gas control.
  

• Corrosion-resistant detector filaments are compatible with most destructive gases and reduce the likelihood of filament oxidation.
  
• Clamshell furnace can heat the quartz sample reactor to 1100 °C. Any number of ramp rates and sequences facilitate customized experiments.
  
• Four gas inlets each for the preparation, carrier, and loop gases permit four-gas sequential experiments, such as TPR/TPO cycles.
• Mass spectrometer port and software integration allows virtually simultaneous detection on both the thermal conductivity detector and mass spectrometer.
  
• Optional Vapor Generator permits analysis using vaporized liquids in an inert carrier stream.
  
• Optional CryoCooler enables the start of an analysis at sub-ambient temperature.

Hardware Advantages:

The AutoChem II features stainless-steel construction, fully automated flow and pressure control, an embedded microprocessor with real-time control, and an intuitive graphical user interface for reactor control. A temperature-controlled, stainless-steel flow path provides an inert and stable operating environment, and reduces the potential for condensation in the flow path.

• Analysis gas may be introduced to the carrier stream by a precision automated loop.
  
• Thermal conductivity detector (TCD) is capable of detecting minute differences in the concentration of gases flowing into and out of the sample reactor. Its corrosion-resistant filaments are operated at constant temperature to prevent thermal runaway.
  
• The extremely low volume of the internal plumbing minimizes peak spreading and significantly enhances peak resolution.

The AutoChem II Technique:

During the TPR, a metal oxide reacts with hydrogen to form a pure metal. This reaction is referred to as a reduction; for example, TPR of a catalyst containing platinum. Argon, which has a very low relative thermal conductivity, is used as a component in the carrier gas.

It is blended in a fixed proportion with hydrogen, the reducing gas with a much higher thermal conductivity. Then the gas mixture flows through the analyzer, through the sample, and past the detector. When the hydrogen and argon gas blend begins flowing over the sample, a baseline reading is established by the detector.

This baseline is established at a low enough temperature so that no reduction of the sample occurs. The baseline level indicated by the detector is that of the thermal conductivity of the two gases in their fixed proportion.

The temperature is then raised and, when a critical temperature is reached, hydrogen atoms in the gas flow react with the sample, forming H2O molecules. The H2O molecules are removed from the gas stream using a cold trap.

As a result, the amount of hydrogen in the argon/hydrogen gas blend inside the analyzer decreases, and the proportion between the two gases shifts in the direction of argon, as does the mixture’s thermal conductivity.

Since argon has a lower thermal conductivity than hydrogen, the mixture’s thermal conductivity consequently decreases. The flowing gas removes heat from the filament more slowly, requiring less electricity to maintain a constant filament temperature.

The instrument records the electrical demand as it changes (this is called the detector signal). The detector signal is recorded continuously over a range of temperatures. When these readings are graphed, the data form one or more peaks. Peaks can be positive or negative.

Chemisorption:

Chemical adsorption is an interaction much stronger than physical adsorption. In fact, the interaction is an actual chemical bond where electrons are shared between the gas and the solid surface. While physical adsorption takes place on all surfaces if temperature and pressure conditions are favorable, chemisorption only occurs on certain surfaces and only if these surfaces are clean. Chemisorption, unlike physisorption, ceases when the adsorbate can no longer make direct contact with the surface; it is therefore a single layer process.

Click on image above to view the Chemisorption Poster