Acid sites, BrSnsted

The activity in consecutive cyclohexene reactions will now be compared. The data presented in Table 2 and in Figure 2 indicate that only strong Bronsted acid sites are active in this reaction. BOR 1, not containing strong sites, is inactive. The activity in consecutive reactions increases in the order BOR 1 < BOR 2 < H-ZSM-5, i.e., in the same order as the strong BrSnsted acid sites content. 

As mentioned above, Pt/HZSM-5 showed higher activity than Pt/NaZSM-5 in the hydrodesulfurization of thiophene. This indicates that the BrSnsted acid site of HZSM-5 in Pt/HZSM-5 catalyst plays an important role for the hydrodesulfurization of thiophene.lt can be assumed that the Brdnsted acid site in the Pt/HZSM-5 catalyst is one site active for the activation of thiophene, whereas R is an active site for the activation of hydrogen. In other words, Pt/HZSM-5 catalyst is a bifunctional catalyst for the hydrodesulfurization of thiophene, in which both Brdnsted acid and platinum metal sites are active sites. 

Fig.l describes the evolution of the number and the strength of acidic sites on Al(Ga)PON catalysts with increasing nitrogen content. The total number of acid sites decreases when the nitrogen content increases for AlPON as well as for AlGaPON catalysts. Previous in-depth works from our laboratory [6, 7] showed that both BrSnsted and Lewis acid sites are present on the Al(Ga)PON surface. The presence of Bronsted acid sites is mainly due to the P-OH species. The presence of Lewis acid sites is probably due to the existence of coordinatively unsaturated tetrahedral Al or Ga atoms. 

Acid sites on sulfated zirconia. (a) BrSnsted, (b) Lewis and [Pg.8]

From the spectra in Figure 14 it is shown that the component 2 corresponding to weak BrSnsted acid centers is dominant in all five spectra. It seems thus that XPS is specially sensitive to the presence of these sites compared to bulk techniques such as IR spectroscopy. This suggests that the weak Brdnsted sites may be surface species. One possibility [49] is that these OH s would be adjacent to a surface silanol ... 

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