Study On Nanosized Ni-based Catalysts For The Hydrogenation Of Native Oils And Fats

Hydrogenation of oils and fats is a technology of preparing hardened oil, which is obtained by hydrogen with fatty glyceride in presence of catalysts. Hydrolysis of hardened oil gives stearic acid which has extensive applications in daily chemical, pharmaceutics and foodstuff. Catalyst is a critical factor of hydrogenation reaction, directly determines the quality and capability of hardened oil and stearic acid, and has an important effect on cost. Hence, hydrogenation catalysts with high activity and low cost are main trend in oils industry and catalysts field.And this dissertation focuses on native nickel-based hydrogenation catalysts for oils and fats.The nano-grade calcium carbonate as the carrier was selected. Palm oil was hydrogenated to test its catalytic performance. The main contents and experimental results are summarized as follows.(1) We studied on the influence of many different carriers on catalytic activity. Nano-grade calcium carbonate as a carrier is cheaper and simply prepared. The industrial nano-grade calcium carbonate was used as the catalyst carrier in this paper. Results show that the catalyst can meet industry requirements in oils and fats hydrogenation. So, nano-grade calcium carbonate as carrier is innovative, and breaks the conventional porous materials as the catalyst carriers.(2) As factors of catalytic activity, the influence of preparation method of active component, loading amount and preparation conditions in catalysts are discussed. Iodine value, XRD and FT-IR were combined. Results reveal that precipitation method is superior to complexed-precipitation and dipping. Catalysts were characterized by means of TG, H2-TPR, XRD and TEM. The preparation conditions of the nano-grade calcium carbonate as the carrier were optimized. Studies have showed that sodium carbonate as precipitant, concentration of nickel nitrate as active constituent is 0.5 mol/L, loading amount of nickel is 30 wt%, precipitation temperature is 65 ℃, p H of solution is about 8, calcination time under 350 ℃ is 2 h, reduction time under 400 ℃ is 2 h, flow rate of hydrogen is 30~40 m L/min, so that catalytic activity is highest. Then based on the Iodine value of product, the reaction conditions were optimized. The best conditions are as follows, the reaction temperature is 200 ℃, hydrogen pressure is 2.0 MPa, reaction time is 2 h, and the dosage of catalyst is about 0.7‰. When we used these conditions to catalyze palm oil hydrogenation, results showed the effect of hydrogenation is the best.(3) Several binary Ni-based supported metal hydrogenation catalysts were prepared by precipitation. According to Iodine value and H2-TPR, XRD and so on, Both metal aluminum and cobalt could be promoters to improve the catalytic activity. The metal aluminum is the best promoter, and when n(Ni):n(Al)=6:1, the Iodine value of Palm oil can be decreased from 32.14 g I2/100 g to 0.33 g I2/100 g, conversion rate is 98.97%.Palm oil hydrogenation was used to inspect the catalyst activity. The results showed that the catalysts with high activity and stable performance, basically reach the industrialization level of imports under optimization conditions and have a good prospect.