*3.2.5 27Al MAS NMR*

**Figure 9** shows 27Al solid-state NMR spectra for ZSM-5 h before and after modification with acid and metal oxide. There is one main peak at 52 ppm in all ZSM-5 h zeolites, which can be assigned to the tetrahedral framework Al [16, 18]. Furthermore, 27Al NMR spectra of HZSM-5 h, Co/NaZSM-5 h, and Co/HZSM-5 h were more noisy than the parent NaZSM-5 h, as a result of minor damages on zeolite framework due to acidity modification and cobalt impregnation. Furthermore, another peak at vicinity near 0 ppm, that is, attributed to octahedral non-framework Al species [21, 22], also appeared in 27Al NMR spectra of Co/NaZSM-5 h and Co/HZSM-5 h.

**Figure 9.** *27Al NMR spectra of ZSM-5 h and Co/ZSM-5 h zeolites.*
