CO2 temperature programmed desorption (TPD) measurements
were utilized to study the basic properties of the prepared catalysts
and the results are shown in Fig. 3. The results clearly demonstrate
that the chicken bone derived catalysts calcined at three different
temperatures (800 C, 900 C and 1000 C) possess broad peaks in
the higher temperature range of 357e600 C, showing the existence
of strong basic sites on the surface of catalysts, thus supporting
the XRD results. Moreover, the results suggest that the
catalyst prepared from chicken bones at 900 C shows greater
uptake of CO2 and therefore, shows greater number of basic sites on
the catalyst surface as compared to catalysts prepared at 800 C and
1000 C (Table 2). The C800 catalyst also shows a small peak in the
temperature range of 585e645 C, which may be attributed to the
presence of very strong basic sites on the surface of the catalyst.
Thus all catalysts show strong basic sites on the surface.