Preparation And Lubricity Of Ethyl Ester Biodiesel From Waste Cooking Qil

Biodiesel is similar to conventional petrodiesel in the combustion characteristics, and it is paid a more attention on a clean and renewable alternative engine fuel. The main obstacle in biodiesel application is from the production cost, especially in the raw material supply and complex production processes. While the waste cooking oils such as animal fat and vegetable oil are very cheap, it will be helpful in food safe and friendly in environment protection if the waste cooking oils are produced into biodiesel. It was detailed the pre-treatment of waste cooking oil, kinetics of biodiesel preparation with cosolvent, the physico-chemical performances of biodiesel and the lubricity of biodiesel in the present thesis. The main research contents are as follows:(1) The physico-chemical performances of waste cooking oil were studied. The results showed that the acid value anhydrous waste cooking oil was increased with the deposition time, while the density was decreased.(2) Both processes of the decoloration and reducing acid value of waste cooking oil were also studied as well. It was found that the optimized parameters for decoloration process was suggested as follows: kaoline concentration was 10wt%; decoloration temperature was 80℃and adsorption time was 30min; At the same time, extraction, neutralization and esterification processes were investigated, and it was found that catalytic esterification with H₂SO₄ was the most efficient method to reduce acid value and the optimized parameters for the esterification was as follows: the molar ratio of ethanol to acid 20:1, H2SO4: 2.0%, reaction temperature 78℃and reaction time 1h. The conversion ratio of free fatty acid was up to 90.65% under the optimal conditions.(3) A novel catalytic process was adopted with potassium hydroxide to prepare biodiesel from waste cooking oil. The results showed that the optimized parameters for transesterification process was as follows: molar ratio of ethanol to oil 12:1, concentration of KOH 1.25 wt.%, reaction time 1.5h and reaction temperature 78℃. Using tetrahydrofuran as cosolvent it could enhance the conversion of waste cooking oil, the kinetics of transesterification was also studied. It was found the kinetic model from the experiment data was a pseudo-second order reaction to waste cooking oil and the activation energy was 7.056kJ/mol.(4) It was studied the physical and chemical performances and the stability of biodiesel which was from waste cooking oil. The main properties of the present biodiesel were in line with nation standards. Because the limitions from high viscosity and low heat value of biodiesel, the ratio of biodiesel with diesel in their blend was suggested no more than 20 wt%. It was also found that less water content and lower storage temperature may lead to higher stability of biodiesel. In addition, antioxidant A could increase the oxidation stability of biodiesel. The biodiesel was easy to be oxidated at high temperature; it would result in increased acid value and viscosity.(5) The tribological performance of the biodiesel was evaluated by MQ-800 four-ball tribometer. The experimental results showed that the lubricity of biodiesel was better than commercial No.0 diesel. SEM and XPS were used to investigate the morphology and distribution of active elements on the rubbed steel ball surfaces. It was showed that the lubrication role was ascribed to the formation of polyester film and high-polarity molecular of fatty acid ethyl ester.