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Preparation Of New Amorphous Alloy, Structural Characterization And Catalytic Hydrogenation Of Glucose,

Posted on:2004-06-09Degree:MasterType:Thesis
Country:ChinaCandidate:H B GuoFull Text:PDF
GTID:2191360092999406Subject:Physical chemistry
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Amorphous alloys represrnt a new class materials with short-range ordering while long-range disordering structure which may proviede pathways to the excellent catalytic properties, such as the high catalytic activity and selectivity, the strong resistance to the sulfur and amine poison, especially the low and even none environmental pollution during heterogeneous catalysis. These topics are still very active because of the industrial reqirements on the atomic reactions and green chemistry. Although the study of amorphous alloy catalysts only covers two decades, plenty of experimental data have strongly shown a good potential for their industrial application.In the present thesis, both the ultrafine and supported Ru-B amorphous alloys, the bimetallic amorphous alloy (Ni-Co-B), and the amorphous alloy with co-metalloid (Ni-P-B and Co-P-B) were prepared by chemical reduction. The catalytic performance of the amorphous alloy catalysts was measured during liquid phase hydrogenation of glucose to sorbitol. The catalytic activity of the Ru-B amorphous alloy was further enhanced by adding the Cr-dopant. The relationship between the structure, surface electronic state of the amorphous alloy and the catalytic performance was systematically studied based on a series of characterization of catalysts, together with the kinetic studies. Meanwhile, the promoting effects of the support on the thermal stability and catalytic activity of the amorphous alloy catalysts have been discussed by considering the interaction between amorphous alloys and the support as well as the dispersing role of the support. Furthermore, by alternating the kinds of the additives and their amount in the amorphous alloys, the modification of several admixtures on the structure of the amorphous alloy has been investigated, which could account for their promoting effect on the catalytic behaviors. The researching work in the present thesis could besummarized as follows.1. Catalyst preparation. By adding KBH4 into a solution containing (1) RuCl3 only, (2) both RuCl3 and CrCl3, (3) both NiCl2 and CoCl2, (4) both NiCl2 and NaH2PO2, and (5) both CoCl2 and NaH2PO2, the ultrafine amorphous alloys of Ru-B, Ru-Cr-B, Ni-Co-B, Ni-P-B and Co-P-B were prepared, which were thoroughly washed with distilled water and stored in in distilled water until the time of use.Meanwhile, the Ru-B/SiO2 amorphous catalyst was prepared by impregnating the SiO2 support with Ru3+ solution, followed by drying, calcinations, and KBH4 reducing. The resulting Ru-B/SiO2 sample was washed in the similar way to that metioned above and also kept in distilled water until the time of use.2. Activity test. All the glucose hydrogenation reactions were carried out in a autoclave containing certain amount of the as-prepared catalysts, glucose aqueous solution and 4.0 MPa hydrogen at a desired temperature. The hydrogenation activity was determined by monitoring the drop of the hydrogen pressure inside the autoclave. The conversion of the glucose and the selectivity to sorbitol was obtained according to the product analysis by either gas chromatograph or chemical titration with Fehlings agent. All the amorphous alloy catalysts exhibited much higher catalytic activity than Raney Ni, which was widely used in industrial process of glucose hydrogenation, showing a good potential in industrial application.3. Correlation of the catalytic performance to the structure of the catalysts.(1). The amorphous alloys usually exhibited much higher activity than their corresponding crystalline counterpart. On one hand, in viewpoint 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. On the other hand, this could also be ascribed to the electronic interaction between the metal and the metalloin in the amorphous alloy. For all metal-B amorphous alloys, the metal always acceted part...
Keywords/Search Tags:Ultrafine and supported amorphous catalysts, Ru-(Cr)-B, Ni-Co-B, Ni(Co)-P-B, glucose hydrogenation, dopant
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