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Korean Journal of Chemical Engineering, Vol.14, No.4, 249-256, 1997
Aromatization of Pentane Catalyzed over Various Metallosilicates
Various metallosilicates were synthesized using a hydrothermal method and characterized by SEM, XRD, 29Si MAS NMR, chemical analysis and surface area measurements. These results showed that they had a MFI structure. The pentane aromatization reaction was carried out over these metallosilicates in a continuous flow reactor at 550℃, He/pentane=3, WHSV=1.5 h-1 and 1 atm. Among the various metallosilicates, [Ga]ZSM-5(20) (52.3%) and [Zn]ZSM-5(40) (37.6%) showed higher aromatic selectivities for pentane aromatization. When [Al]ZSM-5(40) was ion-exchanged with gallium nitrate and zinc chloride, the selectivities for aromatics increased from 23.0% to 35.5% and to 32.7%, respectively. The Si/metal mole ratios of [Ga]ZSM-5 and [Al]ZSM-5 were changed from 20 to 250 and NH3 temperature programmed desorption (TPD) was carried out. As the Si/metal ratio was changed from 250 to 20, the selectivities for aromatics were increased from 5.3% to 52.3% over [Ga]ZSM-5 and from 10.1% to 25.7% over [Al]ZSM-5. NH3 TPD of [Ga]ZSM-5 indicated that the sites of medium acidity play an important role in the formation of aromatics. When H2 and CO were added to the reactant of pentane, the production of methane and ethane increased and that of aromatics decreased.
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