H2-TPR technique is used to analyze the reducibility of PtSnIn/xCa–Al catalysts.
The results are illustrated in Fig. 3.
It can be seen that all catalysts except for c-Al2O3 support have three reduction peaks with a maximum at about 380 C or even lower temperature(peak I), 524 C (peak II) and 798 C (peak III). The peak III is attributed to the reduction of OH groups or aluminum ions of c-Al2O3 support [45].
In general, the peak I may be ascribed to the reduction of Pt oxide species.
It can be observed that the intensity of peak I gradually increases as Ca loading increases up to 1.5 wt.%.
The phenomena imply that the addition of Ca (61.5%) could reduce Pt–Al interaction, which promotes the reducibility of Pt oxides supported on Al2O3.
With the further increase of Ca loading, the intensity of peak I slightly increases and shifts to lower temperature at 368 and 344 C for PtSnIn/1.8Ca–Al and PtSnIn/2.4Ca–Al catalysts,20