| Oil and fat industry is very important in the national economy. Hydrogenated oils has wide application in the food industry. Many studies have pointed out that consuming more hydrogented oils, which have high level of trans-fatty acid isomers, increase the incidente of heart disease, hypertension, high cholesterol and other diseases. Thus the study on the cis-trans isomerizition selectivity of hydeogenation catalysts attracts more and more attention.In this thesis, three series of Ru catalysts were prepared:â… .Ru nanoparticles with differet particle sizes,â…¡.Ru/C catalysts prepared by different methods,â…¢.Sn/Ru/C catalysts with different Sn content. The activity and selectivity of these catalysts for hydrogenation of soybean oil were examined.(1) It is expected that smaller particles will be produced at higher reduction rates for Ru3+ as more Ru0 seeds are produced simultaneously with stronger reducing agents. The preparation using CH3OH as solvent resulted in smaller particles than using water, this may be that CH3OH can decrease the growth speed of Ru seeds.With increasing particle size, the activity of the catalyst decreased. This was attributable to the decrease in the metal surface area. The low activity of the catalyst with the smallest mean size was apparently due to their high surface energy which resulted in catalyst particle aggregation. The selectivity for cis-isomers increased with increasing particle size, and aggregation resulted in the higher trans-isomers selectivity.The catalysts with larger mean sizes had lower metal area, so the active sites were fewer, they adsorbed less C=C bonds, and the effect of steric hindrance were weaker. So they had higher cis-isomers selectivity. Aggregation decreased the hydrogenation active sites but had no effect on the isomerization activity.(2) The Ru/C catalyst, which was reduced by ethylene glycol(EG), was well dispersed and had narrow size distribution. The ethylene glycol was a weak reduction agent, it also acted as stablizer for the produced Ru nanoparticles formed. The catalyst preduced by NaBH4 reduction had smaller mean particle size, but some Ru had aggregated due to their high surface energy. The one that was prepared by impregnation method had wide size distribution and little aggregation. This was because the Ru salt was not evenly distributed. However, when the Ru was reduced at high temperature, the mobility of the small particles formed was high and large particles were formed easily.The catalyst reduced by EG, which was well dispersed and had the largest metal surface area, showed the highest activity and cis-isomer selectivity. The other two catalysts had lower activity and cis-isomer selectivity, because the lower specific surface area and higher steric hindrance, caused mainly by the aggregation and uneven dispersion. (3) The Ru particle size of Sn/Ru/C catalysts increased with increased amout of Sn. With lower amout of Sn, the added Sn can stop the Ru nanoparticle growth. However, the mean size appared larger with the increased amout of Sn. This is because more Sn surrounded the Ru and formed nanoparticles.With the addition of Sn, the activity of Sn/Ru/C decreased, due to the decease in the exposed Ru active sites. Hoerver, Sn could also adsorb H2, the activity did not decrease much with low content of Sn. After the Sn added was increased, the activity decreased sharply for some Ru was covered by Sn.When the content of Sn was increased, the selectivity of cis-trans isomerizition became higher. But when the ratio of Sn and Ru became 5:1, the selectivity did not change with further addition of Sn.The reason for the increased selectivity was that the adding of Sn caused the Ru particles, to be distributed sparsely, decreasing effect of spatial steric hindrance.
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