| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 87 === Searching for a good bifunctional catalyst for hydroisomerization of benzene was the gaol of this investigation. The search started with choosing a proper metal. Nickel, palladium, and platinum were the metals studied. Catalysts of these metals were prepared using Hβ as support. After the metal had been determined, the optimum metal loading was examined. Finally, the effects ofβ-zeolite modifiction were studied. Four modifiedβ-zeolites, designated as Hβ(β-zeolite ion-exchanged with H+ once),HHβ(β-zeolite ion-exchanged with H+ twice), Dβ(β-zeolite dealuminated with HCl for 4 hours), and DDβ(β-zeolite dealuminated with HCl for 6 hours)were prepared. Catalysts of these modified β-zeolite were prepared and their activities in benzene hydroisomerization were investigated.
The catalysts used in this research were all preapred by incipient impregnation. Characterizations of these catalysts were made by BET, XRD, ICP-AES. Activities of these catalysts were tested in a continuous flow tublar reactor under atmospheric pressure.
The results showed 10%Ni/Hβ and 1%Pt/Hβ were more active than 1%Pd/Hβ. Since serious deactivation was found in 10%Ni/Hβ catalysts, the best metal, therefore, was assigned to Pt. The yield of methylcyclopentane on 1%Pt/Hβ reached a maximum at 240-260℃. A further increase in the reaction temperature would lower the conversion of benzene. The reasion for the decrease was the reasion fell in equilibrium region. Activity test of Pt/Hβ catalysts of 0.2-1wt% metal loading showed 1%Pt/Hβ catalyst was the most active one. Increasing the partial pressure of hydrogen could increase the yields of methylcyclopentane but the temperature of maximum yield was also increased. Increasing the number of ion exchange could increase the activity of resulting catalyst. The same effect could be found by the time of dealumination. A significant decrease in the number of acid site was found onβ-zeolite after dealumination. However, the number of strong acid site could be enhanced by dealumination. In the BET measurements, one could found the surface area of β-zeolite was decreased by modifications(ion exchange and dealumination). Since the area of micropores was also decreased, this mean part of theβ-zeolite was destructed by the modification. Among the catalysts prepared from the modifiedβ-zeolite, 1%Pt/DDβ was the most active one. The presence of strong acid sites in 1%Pt/DDβ could be the reason for the catalyst to more active than the others. The result indicated increasing the number of strong acid site could enhance the yield of methylcyclopentane.
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