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Ultrasonic Assisted Preparation Of Amorphous Alloys And Their Catalytic Maltose Hydrogenation Reaction

Posted on:2008-08-02Degree:MasterType:Thesis
Country:ChinaCandidate:D S ChuFull Text:PDF
GTID:2191360218450165Subject:Industrial Catalysis
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As a new type of sweet agent, Maltitol have good taste, reduced caloric value, versatility and its high level of sweetness compared to most other polyols facilitates its commonly use, such as diabetes and fat peoples. Now Maltitol of China mainly depend on import, which were produced by the result of hydrogenation of maltose. It usually use the catalyst of Raney-type Ni, but it is a fragile catalyst, the efficiency of hydrogenation is deficiency and the process of the preparation of Raney -type Nickel catalysts will result in alkali pollution. At the same time they need high temperature and pressure in the action of maltose to maltitol. Amorphous alloys is a new class materials at present with short-range ordering and long-range disordering structure which may provide pathways to the excellent catalytic properties, such as higher catalytic activity and selectivity, stronger resistance to the poison, especially low and even none environmental pollution in the course of catalysts preparation. These topics are still attracting because of the industrial requirements on the atomic reactions and green chemistry.Amorphous alloys was prepared by the chemical reduction method, which can cause the particles of catalyst assemble, and reduce the activity and selectivity. Sound chemistry is the across subject which have been widely used in organic synthesis, polymer science, environment science and the preparation of catalysis material. Ultrasound is a very activity field in the sound chemistry, and can use to device a new way to change the catalysis property.In the present thesis, ultrafine Ru-B, Ru-P, and Ru-B/SBA amorphous alloy were prepared through the chemical reduction with the help of the ultrasonic wave. According to choice the different frequency and power of ultrasound, the property of catalyst can be observed and studied clearly. In this dissertation, we have tried to prepare some special appearance Ru-B alloy. The effect of ultrasound on their structural and electronic characteristics, as well as the catalytic performances, including activity, selectivity were investigated and discussed briefly.I. Catalyst preparation.(1) Ultrasound-assisted preparation of Ru-B amorphous alloy catalysts: By adding KBH4 into a solution containing RuCl3, at the same time adding a ultrasound irradiation, obtain the black ultrfine Ru-B amorphous alloy catalyst.(2) Complex-ultrasound-assisted preparation of Ru–B amorphous alloy catalysts: By adding KBH4 into a solution containing NH3.H2O and RuCl3, at the same time adding a ultrasound irradiation, obtain the black ultrfine Ru-B amorphous alloy catalyst.(3) Preparation of supported Ru-B amorphous catalysts: By impregnating SBA-15 support with a solution containing Ru3+ , then impregnating by ultrasound irradiation, and followed by calcining and KBH4 reducing.(4) Preparation of Ru-P amorphous catalysts: solution containing RuCl3,NaH2PO2 and CH3COONa was mixed in certain temperature or ultrasound irradiation situation and pH value was adjusted with NaOH solution. And finally amorphous alloy Ru-P was obtained.(5) Preparation of special appearance Ru-B alloy catalysts: By adding KBH4 into a solution containing NH3.H2O, RuCl3 and SDBS, obtain the black ultrfine Ru-B alloy catalyst.II. Activity test.All the hydrogenation reactions were carried out in a autoclave containing certain amount of the as-prepared catalysts, 40 wt.% maltose aqueous solution and different pressure 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 maltose and the selectivity to maltitol was obtained according to the product analysis by either gas chromatograph. All the amorphous alloy catalysts exhibited much higher catalytic activity than Raney Ni, which was widely used in industrial process of maltose hydrogenation, showing a good potential in industrial application.III. The correlation of catalytic performance to catalysts'structure(1) The ultrasound didn't alter the amorphous structure of catalyst which can be proved by the XRD and SAED.(2) The ultrasound made the electron transfer change very little which can be proved by the XPS.(3) The ultrasound made the particle size decrease and dispersity increase which can be proved by the TEM and the Hydrogen adsorption.
Keywords/Search Tags:Ultrasounds, ultrafine, (Ru-) amorphous alloy catalysts, maltose, catalytic hydrogenation, maltitol
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