Preparation And Catalytic Performance Of Catalysts For Hydrodeoxygenation Of Oleic Acid

Renewable energy has increasingly becoming an important measure for people to deal with the petrochemical energy crisis, in which biodiesel is one kind of the emerging energy with enormous potentially. The method of translating animal and vegetable oil containing unsaturated fatty acid ester into saturated linear or branched diesel paraffin through hydrodeoxygenation reaction, was called the second generation biodiesel technology. The obtained diesel has some advantages such as high cetane number, low temperature fluidity, and so on, which got the attention of people. In this paper, a series of new type catalysts containing multicomponent metal oxides were prepared and oleic acid is used as model probe of oil to evaluate catalytic performance of those catalysts. The main contents and conclusions are as follows.At first, with incipient-wetness serial impregnation method, a series of NiMo/TiO2-Al2O3 catalysts and NiMoLa/TiO2-Al2O3 catalysts have been prepared. In which, TiO2-Al2O3 composite oxides are carrier and nickel-molybdenum-lanthanum metal oxides are active component precursors. Those catalysts were characterized by ICP-OES, XRD, SEM, TEM, BET, etc. It is concluded that the content of main active component in catalysts had matched the theoretical requirement by incipient-wetness impregnation method. And catalysts had the typical characteristics of mesoporous structure. After calcinated at 550 ?, the catalysts loaded with Ni (6.0%) and Mo (25.0%) basically maintained the crystal phase of the carrier, and metal oxide active components well dispersed on the surface of carriers. Meanwhile, the dispersion of MOO3 was improved by adding La as assistant in catalysts. It could be found that 6.0%Ni25.0%Mo/TiO2-Al2O3 catalyst particles presented a loose distribution, and the surface was rough. In addition, the catalyst displayed a certain degree of sintering phenomenon. However, the sintering phenomenon of the catalyst was significantly overcome after the addition of La element.Meanwhile, one high pressure fixed bed reactor evaluation device for hydrogenation of oils was built independently. And a set of experimental process and evaluation system were established. With 6.0%Ni25.0%Mo/TiO2-Al2O3 as catalyst, the preparation of biodiesel from oleic acid was performed. The search of single factor experiment showed that under 300-370 ?, ratio of hydrogen to oil 300-1200 N(mL/mL), weight hourly space velocity 0.5-5.0 h-1, and pressure 0.5-5.0 MPa, all the conversions of oleic acid were almost to 100%, and the yield of diesel paraffin products were above 70% and up to 84.4%. With the increase of temperature, hydrogen-oil ratio, weight hourly space velocity and pressure, paraffin product yield showed a trend of increasing firstly and decreasing afterward, in which C17 and C18 alkane components yield were the main parts, however C15 and C16 hydrocarbon components yield were very low and less than 10%. C18/C17 ratio of diesel products was about 1, which was less than C18/C15-i6 ratio. Therefore, it can be deduced that the reaction path may be hydrodeoxygenation reaction decarboxylation and decarbonylation reaction>alpha-C and beta-C cracking reaction. Compared the influence of various factors, it showed that C15, C16 hydrocarbon component production were more severe influenced by temperature, and less influenced by other factors. Thus, the appropriate operation conditions were as follows:reaction temperature 340 ?, hydrogen to oil ratio 700 N(mL/mL), weight hourly space velocity 1.0 h-1,and reaction pressure 3.0 MPa.Then, the performance stability of the catalyst was examined under the optimal experimental conditions, and the experimental results showed that conversion rate of oleic acid was close to 100%after 40 hours, but the selectivity of diesel fuel field started to reduce from 30 hours, and the yield of diesel fuel was at about 85.0% from 0 hour to 30 hours, but after 30 hours, diesel yield decreased to about 75.0%.Furthermore, the effect of the La auxiliaries on NiMo type catalysts was explored. Results showed that the addition of La additives helped to improve the activity of catalysts. When the additive content is 1.0% (mass fraction, calculating for La2O3), the activity of catalysts is the highest, and biodiesel yield about 85,5%.Finally, the stability of 6.0%Ni25.0%Mol.0%La/TiO2-Al2O3 catalyst was also investigated under the conditions of temperature 340 ?, pressure 3.0 MPa, ratio of hydrogen to oil 700 N(mL/mL), and weight hourly space velocity 1.0 h-1.The results showed that the catalyst still retained valid activity and selectivity after 60 hours running.