| In twentieth century, considerable petroleum resources are consumed by the rapid development of automobile industry, which make the world that has been facing energy crisis, and promote the steps of development alternative fuels around the world.Biodiesel as a new type of renewable alternative fuels, it is concerned widely around the world because of the excellent burning performance. As an alternative fuel for petroleum diesel, biodiesel is considered an environmentally friendly green fuel. The main component of biodiesel is fatty acid methyl or ethyl ester, and the chemical propertie is very similar with petroleum diesel.Biodiesel has low emission, high flash point, well lubrication, renewable,and many other advantages which comparing with traditional petroleum.As biodiesel contains oxygen and lots of double bonds,which are easy to occur oxidation and polymerization reactions,and have some corrosive for metal, rubber.Therefore, result in the stability of biodiesel is worse than traditional petroleum diesel when it is in the storage,transportation and using.In order to investigate the stability of biodiesel and the usual metal corrosion of auto parts by biodiesel, in this paper,rapeseed biodiesel and 0# diesel for the test oil,which carry out the study for the metal corrosion by biodiesel and the stability of biodiesel, The conclusions are as follows:(1) The strength of biodiesel corrosion metals are iron> copper> aluminum(Corrosion for 45 days,the corrosion rates of three metals are 0.9144‰,0.5952‰and 0.4120 %o),Corrosion was increased along with proportions of biodiesel was increased in oil mixture and the temperature of oil sample(Iron as an example,corrosion for 15 days, oil samples of B0, B50, B100, the corrosion rates are 0.2217‰,0.3043‰,0.3879‰at room temperature, while in 90℃, the corrosion rates are 0.5311‰,1.3618‰,1.5291‰); Study found that the acid value is rapid increased when the oil sample is added to the metal,subsequently decreased. The reason is that the metal has catalytic effect, accelerate the oxidation and decomposition of biodiesel, leading to increased the acid value.Biodiesel in mixed oil sample is higher, this phenomenon is more obvious(Copper as an example,the acid value of B10,B100 are 4.5 mgKOH/g,12.6mgKOH/g at 3 days).After adding antioxidants, the results show that biodiesel added antioxidant will slow down the metals corrosion, and the addition is higher, this phenomenon is more obvious(Iron as an example, corrosion rates are 0.6363‰,0.4418‰after the tertiary butylhydroquinone is added in B100 biodiesel for 0.01%,0.04% at 15 days,and the corrosion rate is of 0.6847‰when antioxidant are not added).(2) Antioxidants can improve the stability of biodiesel, and the addition is higher, the peroxide value is more smaller, the stability of biodiesel is better.This study selected four antioxidants,and the antioxidant capacity are tertiary butylhydroquinone > vitamin E> carotene> pyrogallic acid.The addition of these four antioxidants were 0.04% of the oil sample, the first 3 days of peroxide values were 22.70mmol/kg,26.52mmol/kg, 29.83mmol/kg and35.23mmol/kg at 90℃.The mixed oil sample content biodiesel is higher, the stability is the worse.The addition antioxidants were 0.04% of the oil sample, B0, B100 peroxide values were 0.12mmol/kg,17.46mmol/kg to 15 days at room temperature (18-23℃). The blank oil sample B0, B100 peroxide value were 0.16mmol/kg, 47.15mmol/kg,and the higher temperature, the worse stability of the oil sample. |
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