Study On Synthetic Process Of Dimer Acid By Fatty Acid

Dimer acids are made from C18 unsaturated fatty acid. They have unique physicochemical properties,which contribute to their increasing market demand and price. Dimerisation is relevant to reaction temperature、time and pressure. The catalyst characters also have a strong influence on the yield and selectivity of dimer acids. The common catalyst is active clay. However, it has some drawbacks: low efficiency、great consumption and hard to separate from products. In order to reduce the consumption of active clay、improve the yield and selectivity of dimer acids, the key factor is to improve the catalytic ability of active clay. This work takes oleic acid as raw materials. The active clay was modified by Lewis acid、organic intercalated reagent and cross linking reagent, respectively, the relationships between the kinds and amount of modified reagent and the yields of dimer acids at normal pressure were studied. Also the other factors,such as: free radical initiator、Lewis acid ionic liquid、alkalies cocatalyst and the content of linoleic acid in raw materials, were investigated. The main contents and conclusions of this dissertation are as follows:1、Dimerisation of oleic acid catalyzed by activated clay was studied by orthogonal experimental design. The optimal condition obtained was achieved when the reaction temperature was 240℃, reaction time was 6h, the activated clay amount was 12%(w) of oleic acid, the catalyst promoter Li Cl amount was 1.2%(w) of oleic acid. The highest yield of dimers was 34.6%.2、In order to increase the Lewis acid sites of active clay, it was modified by different inorganic Lewis acid,such as Cu Cl2, Fe Cl3 and Al Cl3.The effects of Lewis acid’s kinds and dosage on the yields of dimer acid catalyzed by actice clay were studied. Results showed that with the increase of Lewis acid’s acidity, Cu Cl2< Fe Cl3<Al Cl3, the yields of dimer acid gradually grow. The suitable Lewis acid is Al Cl3, the suitable amount is 3.3%(w) of active clay, the highest yield of dimer acid is 55.9%.3、In order to improve the interlayer space and lipophilicity of active clay, it was modified by cetyltrimethyl ammonium bromide(CTAB) 、 polyethylene glycol and betaine, respectively. Results showed CTAB had the best effect, when the CTAB amount was 0.6%(w) of active clay, the yield of dimer acids was 54.5%. With the same polyethylene glycol(Mn=350) amount as CTAB, the yield of dimer acids was 45.6%. However,the betaine modified active catalytic ability decreased with the same amount as CTAB. The yield of dimer acids decreased 4.4% compared to active clay.4、To improve the thermal stability of active clay and prevent collapse of its structure under high temperature, it was modified by Zr OCl2. The effect of loading amount of Zr OCl2 on dimer acid yield was investigated. Results showed that the suitable amount is 3.7%(w) of oleic acid, the yield of dimer acids can increase 5.2%, up to 39.8%.5、The dimer acid crude products were characterized by IR and 1H-NMR, the results confirmed the products contained dimer acids.