| Due to the limited traditional fossil fuel and the secondary environment problems produced by burning fossil fuels such as greenhouse, biodiesel, as substitute of fossil fuel have recently attracted significant attention. Biodiesel was often synthesized by transesterification of vegetable oils or animal fats with methanol or ethanol. It mainly consists of mono-alkyl esters of long chain fatty acid, and also contained some free fatty acid and glycerol which was not reacted. Compared with fossil fuel, biodiesel has high oxygen content; better low temperature flow properties, higher cetane number and flash point, and it also can be biodegradable. The pollutants produced in the combustion process reduce significantly.Raw materials were the key factors restricted the development of biodiesel industry and the high cost of raw materials led to the price inversion of biodiesel. At present, all countries screened out the appropriate raw material for biodiesel production. The United States mainly used soybean oil as raw material to produce biodiesel; European countries mainly used rapeseed oil raw material to develop biodiesel industry. In Southeast Asia, they mainly planted palm oil as sustainable materials for biodiesel production. China is a country with a large population and less cultivated land per person. We can’t use farm products as raw materials for biodiesel production. However, our country has a wide range of mountainous and hilly areas, which is suitable for woody oil plants to grow. Woody oil plants have strong stress resistance with a multi-year harvest, and it has a irreplaceable role for biodiesel industry in China. In Hubei province, there are abundant woody oil plant resources, including camellia oil, Tung oil and Chinese tallow which also form many variants now. It is important to screen out the suitable raw material for biodiesel production directly. For those raw materials not suitable for biodiesel production indirectly, it is necessary to improve its performance to make it meet the national standard and analyze the main reason which influence the properties of biodiesel.In this study, three different kinds of oil seeds were collected from Hubei province. According to the biodiesel standards of China, USA and Germany, a criterion has been established for the preliminary evaluation of three kinds of oil seeds as potential biodiesel raw materials. The properties of the biodiesel were improved for those raw materials (Tung oil) which weren’t suitable for biodiesel productions.Tung oil based biodiesel was blended with waste oil based biodiesel to improve the quality. The change of density, viscosity, cold filter plugging point (CFPP), flash point was studied as the percentage of waste oil based biodiesel(WOB). The appropriate proportion was determined and the effects of antioxidants such as tert-butylhydroquinone (TBHQ), butyl-4-methylphenol (BHT), butylated hydroxyanisole (BHA) on the oxidation stability and other properties of the blend were investigated. The change of viscosity and peroxide value of blends were also investigated under accelerated oxidation condition. We also investigated the correlations between the quality parameters of biodiesel and the fatty acid compositions of crude oils containing elaeostearate acid (EA).The results are as follows:(1) Among those oil seeds, three kinds of camellia oleosa seeds were found to be appropriate sources for biodiesel production, including chicken heart camellia, algae skin tongzi camellia, hybrid camellia. However, the other kinds of camellia oleosa were not suitable as raw materials for biodiesel due to the low oil content or high acid value. Because of high content of unsaturated fatty acid, the cetane number, iodine number of Tung oil and Chinese tallow tree based biodiesel very high. And the existence of conjugated triple bond leads to the high viscosity of Tung biodiesel. All these reasons made them not suitable for biodiesel production.(2)The density and flash point of Tung oil based biodiesel and waste oil based biodiesel can reach the national standard. The CFPP of Tung oil based biodiesel can be used a low point so that as cold flow property improver. The oxidation stability of waste oil based biodiesel is good. The viscosity of Tung oil based biodiesel has a little high, and the oxidation stability of Tung oil based biodiesel is bad seriously, only0.3h, far less than the national standard (six hours), influencing the storage stability seriously. The CFPP of wasted oil based biodiesel is a little high, and it will affect the engine start-up performance and limit its low temperature performance.(3) Blending tung oil based biodiesel with waste oil based biodiesel made a balance between the properties of two biodiesels, so that the viscosity of Tung oil based biodiesel was decreased and the fluidity of waste oil based biodiesel was increased.(4) TBHQ showed better antioxidative activity than BHT and BHA, and the addition of TBHQ exhibited little effect on other properties. The blends can meet the national standard (GB/T20828-2007) when1%TBHQ was added. The peroxide value and viscosity of blend had increased after oxidization, and TBHQ inhibited this change.(5) The change in the CFPP was mainly attributed to the saturated fatty acid and the longer the carbon chain, the greater the contribution to the CFPP; the correlation was obtained as CFPP=-8.016+0.668C16:0+7.020C20:0+16.863C24:0-0.265C18:1-0.077EA. The viscosity and the oxidation stability of the blended biodiesels were influenced by the content of EA significantly; the correlation was obtained as viscosity=4.149+0.013C16:0-0.015C18:1+0.021C18:2+0.038EA, lnIP=2.94-0.9821nEA-0.1551nC18:3. The iodine number was mainly attributed to the palmitic acid and EA:the correlation was obtained as IV=126.022-1.647C16:0+0.489EA. Using the above four correlations, the properties of biodiesel blended with TOB can be determined with the fatty acid composition of the raw material. |
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