Studies On The Conversion Rule Of Vegetable Oil By Steam Cracking

Vegetable oil is one kind of clean and renewable energy, carrying out the study of steam cracking of vegetable oils is helpful to further understand the pyrolysis properties of vegetable oils and search the new process path, is meaningful in reality to relieve the crisis of energy and environment and to search substitute of petroleum.In this dissertation,conversion rules about steam cracking of vegetable oils is primarily studied in self-made tubular cracking reactor. Comparative study about conversion rule is carried out with naphtha and soybean oil as feeds with cracking temperature of 700℃,725℃,750℃,775℃,800℃. The results show that when the temperature increases from 700℃to 800℃, the yield of ethylene of soybean oil increases from 18.97wt% to 27.28wt%, while the yield of ethylene of naphtha increases from 10.92wt% to 29.80wt%. At the same temperature, the yield of propylene of soybean oil is smaller than that of naphtha, while the yield of butadiene is larger. In the view of production of ethylene, soybean oil exibits better cracking properties at lower temperature.The effect of composition of aliphatic acid part is studied with soybean oil, sesame oil and peanut oil as feeds. The results show that the aliphatic acid composition of vegetable oil can affect the product distribution and yields of low carbon olefins, the larger the content of saturate fatty acid and oleic acid, the better the properties of cracking are. Considering the cost of feed, the waste oil is used instead of fresh oil, and the results show that the yields of low carbon olefins are similar with fresh vegetable oil, and this indicates that waste oil can partly take instead of fresh vegetable oil in steam cracking.The effect of percentage of soybean oil in mixed oil is researched under certain cracking condition. The larger the percentage, the more easily to crack to produce ethylene and butadiene, but the yield of propylene becomes smaller. With mixed oil in which the percentage of soybean oil is 25% as feed, the effects of temperature, water to oil ratio and feeding velocity are studied, the results demonstrate that to increase temperature and water to oil ratio advisablely is favour of yield of ethylene. The yield of ethylene of mixed oil is 28.48% at 800℃, which is larger than that of heavy feed (diesel) in industry (19-26%).The research indicates that vegetable oil can be used as substitute feed of steam cracking in industry to produce ethylene. Compared with naphtha, when the yield of ethylene is similar, vegetable oil needs lower reaction temperature, which has important significance for industrial application.