Temperature Programmed Reduction (TPR) is used to understand the interaction bet

Question

Temperature Programmed Reduction (TPR) is used to understand the interaction between the catalytic component and the carrier. (Refer to the figure). Explain TPR and how it is performed. What do the peaks at low temperatures (134-140oC) relative to those at higher temperature (219oC) mean? Describe how this is important for catalytic activity.

183 215 134 00 150 200 250 300 350 400 450 50 100 150 200 250 300 350 400 450 500 Temperature (°C) Temperature (°C) 218 140 138 00 150 200 250 300 350 400 450 500 00 150 200 250 300 350 400 450 500 Temperature (°C) Temperature (°C) Fig. 7. H2-TPR patterns of Cuo/CeO2 catalysts calcined at 500 °C: (a) Cuo/CeO2-A, (b) CuOlCeO2-B, (c) CuOlCeO2-C and (d) CuOlCeO2-D

Explanation / Answer

Temperature Programmed Reduction(TPR) is a technique used for chemical characterization of solid materials. It tells us about the most efficient reduction conditions for a solid material.

Application : In the chemical industries, it is mostly used for heterogenous catalysis to find the most efficient reduction conditions for that catalyst. And hence, when catalyst can be reduced easily, for a redox reaction, its turnover number would also be high. Thus, the rate of reaction will be maximum at that point.

Procedure :

Different peaks denote that at that temperature, the reduction is maximum. Also, area under the peak denote the extent of reduction. Now, if more than one peaks are appearing at different temperature as in the graphs in the question, this shows that the metal can exist in two different oxidation states and at different temperature can be reduced to them differently. Above graphs are given for copper, which at low temperatures reduces to Cu+ and at high temperatures reduces to Cu2+ . That's what different peaks at different temp. tell us about the material.

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