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Co: Mo = 1:2

__\ Mo

100 200 300 400 500 600 700 800

Temperature (°C)

100 200 300 400 500 600 700 800

Temperature (°C)

Figure 23. Temperature programmed oxidation of all the carbonaceous species formed over a CoMo/SiO2 catalyst after disproportionation of CO at 700 °C, compared to monometallic Co/SiO2 and Mo/SiO2 catalysts, treated in an identical way. Reprinted with permission from [29], B. Kitiyanan et al., Chem. Phys. Lett. 317, 497 (2000). © 2000, Elsevier Science.

ratio in the Co-Mo/SiO2 catalysts. Figure 24 shows that, in agreement with the TEM characterization, the TPO of the Co:Mo = 1: 2 sample indicates that this sample produced mostly SWNTs, with a small amount of amorphous carbon. An increase in the Co:Mo ratio did not enhance the production of SWNTs, but it did accelerate the formation of MWNTs and graphitic carbon, as shown by the increasing size of the peaks in the region 600-700 °C. From the TPO data, selectivity values were estimated by curve fitting. They were 57% SWNT and 31% MWNT for the Co:Mo (2:1), 80% SWNT and 4% MWNT for the Co:Mo (1:1), and 88% SWNT and 4% MWNT for the Co:Mo (1:2). It is important to note that, in all cases, the quantitative data agreed very well with the qualitative observations made by TEM.

Raw HipCo material w Q

Raw HipCo material

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