Study On Catalytic Properties Of Nickel Loaded On ZrO₂ And ZrO₂ Based Composite Support For Benzene Hydrogenation

In the first part of this thesis, ZrO₂ support was prepared by microemulsion (M) and precipitation (P) methods. Using ZrO₂ as support, Ni/ZrO₂ catalysts were prepared by impregnation. The effect of support prepared method on the activity of Ni based catalyst for benzene hydrogenation was tested. The supports and catalysts were characterized by X-ray diffraction (XRD), Temperature-programmed reduction (TPR), Temperature-programmed desorption (TPD) of H₂ and benzene and nitrogen adsorption. It was found that Ni/ZrO₂ (M) catalyst exhibited higher activity than Ni/ZrO₂(P) for benzene hydrogenation. As compared with ZrO₂(P) prepared by precipitation, the ZrO₂ (M) prepared by microemulsion had larger BET surface area. The Ni/ZrO₂ (M) catalyst had larger active surface area, more adsorption center, the weaker intensity of H₂ adsorption than Ni/ZrO₂ (P), which was favorable for benzene hydrogenation.In the second part, a series of ZrO₂-Al₂O₃ composite supports with different ZrO₂ content were prepared by impregnation precipitation method (I-P). The composite supports were used as support of nickel catalysts prepared by impregnation. The effect of Zr/Al atomic ratio on the Specific areas of supports and the activity of Ni catalyst for benzene hydrogenation were tested, and the results were compared with Ni catalyst loaded over single support. It was found that the S_BET of composite supports decreased with increase the Zr/Al atomic ratio, the Ni catalyst supported on the composite support ZA20(I-P), where Zr/Al atomic ratio was 0.14, exhibited higher activity for benzene hydrogenation than that on the single-component support. Zirconia exist as amorphous phase in ZA20(I-P). Ni/ZA20 was more easily reduced than the other catalysts, and the more numbers of adsorption center existed.The ZrO₂-Al₂O₃ composite support (Zr/Al atomic ratio 0.14) was perpared by microemulsion(M) and co-precipitation(C-P) methods, and compared with ZA20(I-P). Effect of support preparation method on catalytic activity, reduction and adsorption capability of Ni/ZA20 were studied. The results indicated that the order of catalytic activity was Ni/ZA20(I-P)＞Ni/ZA20(M)＞Ni/ZA20(C-P), and Ni/ZA20(I-P) can adsorb more reactants to react, favoring in the reaction.In the third part, amorphous Ni-B alloy was fixed on ZA20(I-P) andγ-Al₂O₃ by impregnation and chemical reduction. The result indicated that compared with unsupported Ni-B catalyst, the weight of nickel in the bulk composition on amorphous Ni-B/γ-Al₂O₃ and Ni-B/ZrO₂-Al₂O₃ was decreased, and their surface area of active nickel was 7 and 12.2 times of unsupported Ni-B alloy, respectively. The thermal stability of Ni-B/ZrO₂-Al₂O₃ was higher and more reactants could be adsorbed on its surface, leading to higher catalytic activity for benzen hydrogenation.