I ran a CO-TPR experiment on an gamma-alumina supported iron catalysts. I'm getting two invert peaks, a small peak at the beginning and a large peak at the end of the temperature range. Iron oxide is normally reduced at around 300C, 480C, and 600C, while I'm just getting the second peak around 480C. I used 10%CO/90%Ar blend as the analysis gas. Sample was degassed under flow of He at 500C, then cooled down to ambient prior to the experiment. Does anyone have any idea why the invert peak is showing up? I have attached the TPR graph and also the experiment log.
The gas you used was CO in He not in Ar, as it is seen from exp. log. Helium has higher thermal conductivity than CO , that is why signal incereases, when consumption of CO takes place.
Dear Colleagues, I have a question related to this topic. I appreciate if you answer my question also.
TPR test is usually performed at atmospheric pressure, what is pressure effects on the TPR results?
Increasing of pressure has a positive effect on reducibility of metal oxides through increasing kinetic.
So the time of reduction would be lowered by increasing of pressure.
Also the overall percentages of metal ions would be increased by increasing pressure during reduction proscedure in comparison with atmospheric pressure in the same time.
I am not sure, but increasing pressure during H2 reduction may accelerate hydrogen spillover. That's why the kinetic would be accelerated by increasing H2 pressure.
I highly recommend an article titled *hydrogen reduction of nickel oxide under High pressure* written by Toshio Kurosawa and their colleagues.
With Best regrads,
For consumption, you will observe the positive peak and for desorption of surface species, you may observe the dipping or inverted peaks in TPR
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