Synthesis and Evaluation of Canola Oil Derived Biolubricants Using Heterogeneous Catalysts
Somidi, Asish Kumar Reddy
The current research is focused on the preparation of a value-added product called biolubricant using canola oil and canola biodiesel as feedstocks. The presence of unsaturation among the selected feedstocks limits their application as a potential lubricant because unsaturation renders unfavourable oxidative and thermal stability, and poor lubricity when used as a lubricant. The two-step reaction pathway chosen to remove unsaturation in both the feedstocks and make potential lubricants are: (1) epoxidation of unsaturated fatty acids in the canola oil/canola biodiesel followed by epoxide ring opening and vicinal di-O-acetylation with acetic anhydride; and (2) epoxidation of unsaturated fatty acids in the canola oil/canola biodiesel followed by epoxide ring opening and O-alkylation with 1-propanol. This research work is primarily focused on the preparation and development of heterogeneous catalysts using metal oxides or metal supported catalysts for the above-mentioned two-step synthesis procedure. The research work is divided into four phases. The first phase involved preparation of a heterogeneous catalyst for the epoxidation of unsaturated fatty acids in the canola oil. Sulfated tin oxide demonstrated promising activity with 100% conversion of canola oil to epoxidized canola oil (biolubricant base oil) at the optimum conditions such as: temperature (70oC), ethylenic unsaturation in the canola oil to H2O2 molar ratio (1:3), ethylenic unsaturation in the canola oil to acetic acid molar ratio (1:2), catalyst loading of 10 wt% with respect to feed taken and reaction time of 6 h. Catalyst characterization was made to study the properties of sulfated-SnO2 that promoted epoxidation reaction. Co-ordination of sulfate ions to the tin oxide surface after the calcination at 550oC is found necessary because sulfate ions induce Lewis and Bronsted acidity to the catalyst surface. The epoxidation of canola oil reaction followed pseudo first-order reaction and the calculated activation energy was found to be 18 kcal/mol. The second phase involved with the preparation of vicinal di-O-acetylated canola oil (biolubricant type 1) using heterogeneous catalyst by epoxide ring opening and vicinal di-O-acetylation of epoxidized canola oil. Catalyst screening tests showed that sulfated-ZrO2 is highly selective in complete conversion of epoxidized canola oil to vicinal di-O-acetylated canola oil. The optimum conditions obtained from the Taguchi experimental design are: reaction temperature (130 oC), epoxy to acetic anhydride molar ratio (1: 1.25), 16 wt% of catalyst loading with respect to the quantity of feed (epoxidized oil) taken, and a reaction time of 1 h 15 min. The reaction was found to follow the second-order and the calculated activation energy was 23 kcal/mol. The third phase of the work is focused on the development of a single heterogeneous catalyst that is active for both epoxidation, epoxide ring opening and vicinal di-O-acetylation reactions in a single pot. 10 wt% MoO3/Al2O3 was found to be highly active and selective in complete conversion of unsaturated canola oil to vicinal di-O-acetylated canola oil in a single pot in minimum reaction time. The optimum conditions obtained based on response surface methodology are: unsaturation in the canola oil to tert-butyl hydroperoxide molar ratio (1: 2.25), 10 wt% MoO3/Al2O3 as catalyst for both steps, 12 wt% of catalyst loading with respect to amount of canola oil taken, epoxide to acetic anhydride molar ratio (1:2) and a reaction time of 5 h 30 min. These optimum conditions are also applied for the one-pot synthesis of vicinal di-O-acetylated canola biodiesel and complete conversion was found to happen in 4 h and 15 min. The developed one-pot synthesis procedure was found effective in minimizing work-up procedures for product extraction, minimized catalyst usage and reaction time. Further, evaluation and comparison of physicochemical properties of vicinal di-O-acetylated canola oil and vicinal di-O-acetylated canola biodiesel were also made to identify their application as a lubricant for various applications. In the fourth phase O-propylated canola oil (biolubricant type 2) was synthesized from epoxidized canola oil by epoxide ring opening and O-propylation reaction. Al-SBA-15 catalyst with Si/Al ratio 10 showed promising activity with 100% conversion at the optimum conditions (based on response surface methodology). Catalyst characterization showed that impregnation of aluminum in the crystal lattice of SBA-15 promoted epoxide ring opening and O-propylation reaction. The optimum conditions are temperature (100 oC), epoxy to 1-propanol molar ratio (1:6), catalyst loading of 12 wt% with respect to epoxidized canola oil taken, and a reaction time of 6 h. The reaction kinetic showed that epoxide ring opening and O-propylation reaction followed second-order reaction, and the apparent activation energy was 12 kcal/mol. Al-SBA-15 was found to be an efficient catalyst for the preparation of O-propylated canola biodiesel. 100 % conversion was achieved in 6 h reaction time. Determination of physicochemical properties of O-propylated canola oil and canola biodiesel showed that they meet the specifications of transmission gear oil and anti-wear hydraulic oils.
DegreeDoctor of Philosophy (Ph.D.)
DepartmentChemical and Biological Engineering
CommitteeHwang, Hui; Niu, Catherine; Soltan, Jafar; Foley, Stephen
Copyright DateDecember 2016
Biolubricants, Metal oxide catalysts, Kinetic studies, Canola oil, Canola Biodiesel