Comparison of crystallization rates of [Al]-and [Ga]-MFI-type zeolites

Characterization of bifunctional Pt/H[Ga]ZSM5 and Pt/H[Al]ZSM5 catalysts

“…1a and b) the peaks characteristic of the MFI structure [25]. They seem to have high purity and crystallinity, as no extra-framework Ga or Al were detected (absence of Ga 2 O 3 or Al 2 O 3 signals).…”

Incorporation of Gallium into Zeolites: Syntheses, Properties and Catalytic Application

“…A relatively fast crystallization of [Ga]-ZSM-5 has been reported by Gianetto et al They compared the rates of crystallization for [Al]-ZSM-5 and [Ga]-ZSM-5 (Si/Al and Si/Ga ratios amounting to 58 and 60, respectively) at 170 °C from sodium aluminosilicate/gallosilicate gels containing tetrapropylammonium bromide. The pH value of nearly 9 adjusted by the addition of sulfuric acid guaranteed optimal condensation of Al, Ga, and Si oligomers and enhanced nucleation and growth of zeolite crystals.…”

Performance of MFI Zeolite Catalysts in n-heptane Conversion Reaction Test

“…Ni-ion exchange ZSM-5 was less effective in the aromatization of n-heptane that Ag-and Zn-HZSM-5 [82,83]. n-Heptane conversion over Metal-HZSM-5 obtained by ionic exchange occurs via a complex sequence of cracking, dehydrogenation, and/or H transfer, oligomerization, isomerisation, cyclization, β-scission (scheme 1) [12,49,82,83].…”

“…Although the metal-modified HZSM-5 catalysts exhibit a significant improvement in the selectivity to total aromatics, the detailed reaction pathways of the aromatization on such catalysts have not yet been understood but extensively discussed. Giannetto et al [12,13] suggested that the direct aromatization of n-hexane and n-heptane yielding toluene, C 8 aromatics and benzene, respectively, took place over Ga-HZSM-5 catalysts, thereby proposed that the direct aromatization occurred via the * email: gisandu@yahoo.com and adi_spac@yahoo.com dehydrogenation step on the metal sites, followed by cyclization over acid sites. Recent reports on the aromatization of n-heptane over Zn-HZSM-5 and Ga-HZSM-5 catalysts proposed that the aromatization started with cracking of n-heptane, followed by oligomerization to higher alkenes, before the dehydrocyclization steps.…”