| The hydrogenation of natural fats and oils has been widely used in food industry, for example, the stearin obtained from coconut oil can substitute cocoa grease or is used as raw material of margarine. In addition, by means of hydrogenation of Carbon-Carbon double bonds in oils as well as in fatty methyl esters, many of chemical industry raw material and biological diesel oil can be obtained, which for the future energy source and the environment protection has significant meaning. All of these processes involve the catalysis hydrogenation. Therefore, the study of the preparation of high active catalysts for hydrogenation is of great significance.Many studies of catalysts for hydrogenation of natural oils have been made, in which Cu-Ni bibasic catalyst and Ni unitary catalyst are the two mainstreams. For the food industry, the Ni unitary catalyst is mainly adopted because of its high activity, and the hydrogenation products is of high anti-oxidation stability during their storage at room temperature. There are a lot of preparation methods of the catalysts which active component precursors also have many forms.For the supported catalyst, the crystal structure of supports, the surface area, the pore structure and pore distribution of the catalysts, have influences on hydrogenation activities and selectivities. Thus, suitable preparation method and appropriate supports is the key to prepare industrial catalyst with high activity.In recent years ,the amorphous alloy catalysts have been widely studied because of its high activity and selectivity. Amorphous alloy catalysts have much special character and good application prospectIn this paper, the Ni-B/SiO: amorphous alloy catalyst has been prepared by using chemical reduction method .In which NiCl2.6H2O was used as the precursor of active component Ni , NaBH4 was used as reduction agent ,and the special SiO2 prepared by us was made as a support. The prepared catalyst exhibits very high activity when it was used in the hydrogenation of natural oils. Thus the catalyst has potential industrial application prospect. The preparation conditions and the operation conditions ofNi-B/SiOi amorphous alloy catalyst were studied. The catalyst was also characterized by XRD, DTA - SEM, IR as well as the measurement of BET surface area in order to investigated the relations between macroscopic properties and microscopic structure. Some significant results were obtained.1 Preparation conditions of the Ni-B/SiO2 amorphous catalyst: the content of Ni is 20 wt %, KBH4: Ni2+ = 1.5 : 1, the concentration of KBH4 is 2 mol-lAln the supported Ni-B/SiO2 amorphous catalyst, Ni-B was dispersed on the support surface with superfine particle. Due to the support, the dispersity and thermal stability of the amorphous alloy were enhanced, and the congestion of Ni-B was inhibited.2 The operation conditions of the Ni-B/SiO2 amorphous catalyst: the effect of hydrogenation time, hydrogenation temperature, hydrogenation pressure and catalyst concentration on reactive activity was researched. The suitable operation temperature of catalyst was 180-200℃, hydrogen pressure was 0.2M Pa, and reaction time was 60min.3 The results of XRD, DT, SEM, IR and the measurement of BET surface area of the catalyst were as follows:DTA shows that due to the SiOi support the congestion of Ni-B was inhibited. Active component was under high dispersion state.XRD exhibits the amorphous character of the catalyst. After be heated, the catalyst was under thermodynamic stable state and was crystallized. But the heating didn't influence the hydrogenation activity of the catalyst.SEM shows that the particle size distribution character of the catalyst The particle size distribution and active component of the catalyst whose activity is better are uniform. Active component congest on the catalyst surface.BET surface area exhibits that the catalyst has bigger pores which is in favor of reactant diffusion.IR illustrates that the Ru-B/SiC^ amorphous catalyst tends to anti-type hydrogenation. |
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