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Temperature Programmed/Pulse/Vacuum/Flow


Our laboratories have two very versitile systems in which we can do many temperature programmed, pulse/vacuum/flow experiments. The AutoChem 2020 is a fully automated instrument with four independently calibrated mass flow controllers capable of flowing a wide range of gas compositions.

Experiments can be programmed with a user-defined sequence in order to perform pretreatment and analysis procedures automatically by the instrument. The available furnace temperature range is from subambient (-70oC with a CryoCooler) to 1100 oC.

The Autochem features include:

Temperature-programmed reactions (desorption, reduction, and oxidation)
Pulse chemisorption for active metal surface area and distribution analysis
Equipped with a vapor generator which can precisely dose vapor as an analysis gas into the reactor
External ports available to allow products from the reaction chamber to be directed to a mass spectrometer or other external detector.
Single-point BET surface area analysis by physical adsorption with in situ pretreatment feature

 



Our in-lab constructed temperature programmed and pulse/vacuum/flow system is highly versatile. Some of its features are:



Built in TCD detector for separate TPR
Newport i-series controllers for DAQ/control
Alcatel Vacuum system (10-5 Torr)
Valco electronic actuated switching valves
On-line mass spectrometry
 



We perform a wide range of experiments using this system, including:Valco electronic actuated switching valve

- Temperature programmed:
- Oxidation/Reduction/Sulfidation/Reaction/Desorption
- Pulse chemisorption
- Isotopic labeling studies (transient and steady-state switches)
- Combination experiments (Reaction + Mass Spec + TGA/DSC)


Temperature-Programmed Reduction (TPR) determines reduction sites present in the catalyst bulk and reveals the temperature at which the reduction at each site occurs.  The TPR analysis begins by flowing an analysis gas through the sample, usually at ambient temperature. While the gas is flowing, the temperature of the sample is increased linearly with time and the consumption of hydrogen (or other reductant) by adsorption/reaction is monitored.

To examine competitive adsorption effects between separate gas phase species and to assess how the adsorption sites could be affected through this competition, we can perform a variety of Temperature Programmed Desorption (TPD) experiments using one or more adsorbates and after varying pre-treatments.  In a variation of this experiment, a Temperature Programmed Reaction (TPRxn) can follow adsorption by allowing a species in the gas phase to react with the adsorbed species.