| As an organic solvent, organic raw material and a composition of the synthesis process of polyamide fiber products, Cyclohexane can be gained by Benzene hydrogenation and oil fractions recovery. With the requiements of Cyclohexane increasing rapidly, oil fractions recovery can not afford it in quantity and quality, so Benzene hydrogenation has been the main method to Cyclohexane. In pace with the progress of refining coal coking products, it has been an important study field for Benzene refined form coking crude Benzene to Cyclohexane. Currently, the active component in Benzene hydrogenation catalysts is mainly noble metal. The common method of improving catalytic activity is to increase the loading, which leads to increase the consumption of noble metal and reduce economic benefit. In order to reduce process cost, strengthen production capacity and the reasonable application of natural resources in the field of coal-coking refined process, it is imperative to develop a kind of economical and practical benzene hydrogenation catalyst with lower loading. In this paper, the catalysts were prepared using volumetric immersion method which was used in benzene hydrogenation by integral cyclohexane reactor. The properties were characterized by XRD, TPR and IR etc. Taken the conversion rate and selectivity of Cyclohexane as the evaluation standard of catalysts, the benzene hydrogenation catalytic process and catalysts of preparating Cyclohexane were studied in the aspects of reaction operating conditions optimization, support selection and additives, support and preparation process conditions. The main conclusions were:(1) With Ni(NO3)2 precursor, Ni/γ-Al2O3(loading mass percent is 30%, Ni-30%) catalyst was synthesized. The effect of reaction temperature(T), Hydrogen-Benzene mole ratio(H2/C6H6), Benzene liquid space velocity(VLSP) and reaction pressure(P) on Ni-based catalyst activity was investigated and the optimum operation condition obtained by orthogonal test was:T 220℃, H2/C6H6 6:1, VLSP 0.5-1.Oh-1 and P 2.0 MPa.(2) y-A]2O3 and TiO2 were chosen as catalyst supporters respectively, then Ni/γ-Al2O3 and Ni/TiO2 (Ni-10%) catalysts were parepared and evaluated on the same operating conditions. The results show that the conversion rate of Ni/γ-Al2O3 is 30% and the conversion rate of Ni/TiO2 is only 8.06%. XRD and H2-TPR show that NiO is distributed uniformitily on the surface ofγ-Al2O3 and crystallized on the TiO2.(3) Ni-based catalysts, withγ-Al2O3 catalyst support, were parepared by loading four different additives(La, Ce, Mo, Cu, loading mass percent is 1%) and evaluated on the same operating conditions. The experimental results show that the conversion rate of La-Ni/γ-Al2O3, Cu-Ni/γ-Al2O3, Ce-Ni/γ-Al2O3, Mo-Ni/γ-Al2O3 is 65.17%,58.91%,46.92% and 36.49% respectively, which means the addition of La and Cu can remarkably enhance the activity of Ni catalysts. There are no diffraction peaks of additives and NiO in the XRD diffraction spectrum diagram, which means NiO is distributed uniformitily on the supporters'surface. The starting reduction temperature of Cu-Ni/yγ-Al2O3 is 200℃and others are all over 400℃by analyzing the results of H2-TPR. IR shows that the offset degree of Ni-O bond is different when different additives were added in the catalysts.(4) P-Ni/TiO2 and P-Ni/γ-Al2O3 (P-1%, Ni-10%)catalysts were parepared through phosphoric acid modification. The catalytic performances were investigated at the same operating conditions. The results show that NiO is distributed uniformitily on the surface of support; the conversion rate of benzene is 57.17% and 25.10% respectively. So the catalyst activity can be increased remarkably through phosphoric acid modification. But excessive phosphoric content results in reduction of the activity because of NiO crystallization.(5) With the catalyst of P-Ni/γ-Al2O3(P-1%, Ni-10%), the effect of the calcination temperature on the catalyst activity was studied. The results show that the conversion rate in the range of 350-600℃is the highest one,57.17%, at the calcination temperature of 450℃...
|
PDF Full Text Request