fig1

Figure 1. (A) ²⁷Al single-pulse MAS NMR spectra of HZSM-5 before and after steam treatment at 100 ~ 500 °C for 2 h. Note that the intensities have been normalized by mass. ²⁷Al MQ MAS NMR spectrum of HZSM-5 (B); HZSM-5-200-2 (C); HZSM-5-300-2 (D); HZSM-5-300-2-NH₄ (E) and HZSM-5-500-2 (F). All samples are fully hydrated.