Amorphous Alloy Preparation, Characterization, And In The Hydrogenation Of Nitriles

Amines were very important chemical intermediates and applied widely in chemical synthetic industries. Some of them were synthesized from the hydrogenation of nitriles.Acetonitrile was a byproduct in the acrylonitrile production, and it possessed 1.0 -2.0% of acrylonitrile output, which had a huge mass every year all over the world. At the same time, It become a troublesome and urgent question in some area how to deal with acetonirile.Catalytic hydrogenation of acetonitrile to ethylamines was a potential process for both the utilization of acetonitrile and the production of ethylameines, and also an useful model reaction.Amorphous alloy was a kind of new materials with short-range ordering while long-range disordering structure, and as a catalyst, it was of higher activity, better selectivity, and stronger resistance to the sulfur and amine poison as well as less or even no environmental pollution during the catalyst preparation and its application.In the present thesis, the four supported amorphous alloys catalysts, Co-B/SiO₂, Co-Fe-B/SiO₂, Co-B/Al₂O₃ and Co-Fe-B/SiO₂-Al₂O₃ were prepared by chemical reduction. Their catalytic performances were measured by hydrogenation of acetonitrile both in gas phase and in liquid phase. The relationship between the catalytic performances and the structural and electronic characteristics incluing promoting effect of adopted metal and support was systematically studied by combining a series of characterizations and the kinetic studies. Furthermore, uniform sphere and 1D chain structure of Co-B amorphous alloy materials were synthesized by ammonia coordination combining ultrasonic wave and sulfur alcohol inducing self-assembling respectively, and their property of catalysis was evaluated, their mechanism of formation and relationship between structure and performance were also discussed.1. Catalyst preparation. Supported Co-B/SiO₂ amorphous catalyst was prepared by impregnating SiO₂ support with Co2+ solution, followed by drying, calcining, and reducing with KBH4. Other supported amorphous catalysts were prepared in the similar way. The Co-B amorphous alloy with uniform sphere and 1D chain structure were synthesized by ultrasonic assistant and self-assembly induced by surfactant respectively. All amorphous catalysts obtained were stroed in ethanol for use.2. Activity test(1) The catalytic hydrogenation of acetonitrile was carried out in continueos feed in fixed bed and in branch in an autoclave containing certain amount of supported amorphous alloy catalysts.(2) Adding a certain amount of Co-B amorphous alloy material with uniform sphere in an autoclave, the reaction condition of hydrogenation of acetonitrile at 3.0 MPa and 110℃.3. The relationship between catalytic performance and the structure of catalyst.(1) The supported amorphous alloys usually exhibited good catalytic performance. On one hand, in view point of the structural effect, this could be attributed to the unique amorphous structure (i.e., the short-range ordering but long-range disordering structure), the homogeneous distribution of the active sites, and the highly coordinative unsaturation of these active sites and the electronic interaction between the metal and the metalloid in the amorphous alloy also had effect. For all amorphous alloys, the metal always accepted partial electrons from the alloying B, making it electron-enriched while the B electron-deficient. On the other hand, dispersion of amorphous alloy particles on a suitable support seemed favorable for improvement of its thermal stability and activity. Such promoting effect could be interpreted in terms of the interaction between amorphous alloy and support as well as the dispersion of active metal.(2) The activity raise of the supported Co-B amorphous alloy by doping Fe could be accounted for by considering its dispersion effect.(3) The supported amorphous alloys usually exhibited much higher activity than their corresponding crystalline counterpart. At higher temperature, the amorphous alloy catalysts lost its catalytic activity significantly, possibly due to the crystalline transformation from their amorphous structure, the deconstructure of the metal-metalloid, as well as the agglomeration of alloy particles, which cause an abrupt decrease in the active surface area.(4) The Co-B amorphous alloy material with uniform sphere had much higher catalytic activity than the traditional Co-B amorphous alloy material. The reason could be that the homogeneous dispersion of the catalyst particles and the accretion of the activity surface area. Meanwhile, ultrasonic wave enhance the interaction between the metallic cobalt and the metalloid B.