Modification of amorphous alloy catalysts(2)


As additives, rare earth metals mainly modify the structure and properties of amorphous alloys from two aspects: geometric effects and electronic effects. The catalytic activity of Ni-P—Ce ultrafine amorphous alloy prepared by chemical reduction method was studied, and it was found that CE additives could significantly improve the benzene hydrogenation activity and thermal stability of ultrafine Ni-P amorphous alloy catalyst. Analyzing the reasons, there may be two aspects: first, Ce increases the disorder and dispersion of ultrafine Ni-P amorphous alloys, thereby increasing the number of surface-active centers; Second, ce has a synergistic effect with the catalytic active center, or changes the electronic structure of the Ni-P amorphous active center. The effects of heavy rare earth elements (Dy, H0, Er, Tm, Yb, Lu) and light rare earth elements (Ce, Pr, Nd) on the hydrosulfur resistance of Ni.B amorphous alloy catalysts were studied. The catalysts were characterized by XRD, DSC, CO chemisoption, TPR and TPD. The results show that there is a certain interaction between rare earth oxides and Ni-B alloys. The combined effect of the electronic and geometric effects of rare earth RE on Ni.B alloy leads to an increase in the number of active centers, an increase in the surface area of active Ni, a significant increase in hydrogen absorption and a weakening of hydrogen absorption strength. At the same time, the thermal stability, activity and sulfur resistance of Ni-B alloy were improved, and the activation energy of benzene hydrogenation reaction of Ni.B amorphous alloy catalyst was reduced, which increased the hydrogenation activity.
  
As a new type of catalytic material, amorphous alloy catalysts do have obvious characteristics, and there is a catalytic active center on the surface of crystalline alloys, which may be an active center composed of groups composed of several atomic groups. Amorphous alloy is a promising catalyst because it has superior activity, selectivity and poisoning resistance than crystalline alloy, especially less environmental pollution during the preparation process.

 

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Reni nickel catalyst science knowledge(1)

Physical and chemical properties: Reni nickel catalyst before activation is silver-gray amorphous powder (nickel-aluminum alloy powder), with a moderate degree of flammability, partial activation in the presence of water and the production of hydrogen easy agglomeration, long-term exposure to air is easy to weather. Nickel-aluminum alloy powder is activated into gray-black particles, accompanied by active hydrogen, extremely unstable, oxidative combustion in the air, must be immersed in water or ethanol for preservation. It was first used by American engineer Murray Rainey as a catalyst in the hydrogenation of vegetable oils. The preparation process is to treat nickel-aluminum alloy with concentrated sodium hydroxide solution, in this process, most of the aluminum will react with sodium hydroxide and dissolve, leaving a lot of micropores of different sizes. In this way, the surface of Raininickel is a fine gray powder, but from a microscopic point of view, each tiny particle in the powder is a three-dimensional porous structure, this porous structure greatly increases its surface area, and the large surface area brings high catalytic activity, which makes Raininickel widely used as a heterogeneous catalyst in organic synthesis and industrial hydrogenation reactions. Since "Rainey" is a registered trademark of Grace Chemicals, strictly speaking, only products manufactured by the company's Davidson Chemical Division can be called "Lanny Nickel". The term "metal backbone catalyst" or "sponge-metal catalyst" is used to refer to catalysts with a microporous structure and physical and chemical properties similar to Raney nickel.