Study On Preparation Biodiesel From High Acid Value Oil And Refining Glycerine

In this thesis, the preparation of biodiesel from high acid value (AV) oil, such as cooking oil,acidification oil and waste oil,was studied.The preparation process of biodiesel,the kinetic factors and the relationship between low temperature property and the molecular structure of fatty acid methyl ester were systematically discussed.Furthermore,the salutions to improve low temperature property of biodiesel and refining processof the by-product glycerine were investigated. The main content and results are summarized as follow:Used as catalyst in pre-esterification, sulfuric acid, phosphoric acid, toluene-p-sulfonic acid, iron trichloride and toluene-p-sulfonic acid was compared.The results show that toluene-p-sulfonic acid is the best catalyst. It has good catalytic activity and it hardly dissolves in the oil but can dissolve in the methanol. The pre-esterification oil can transesterize directly without washing. The process is environmental. The methanol with catalyst can be used again in the next pre-esterification after dehydration. Most of catalyst can be recovered. It helps to cut down the cost.In the pre-esterification stage, the effect of mole ratio of alcohol and acid, dosages of catalyst, reaction time and reaction temperature was investigated. The optimum conditions for pre-esterification are got by orthogonality experiment. The result shows that the optimum conditions are as follow: mole ratio of alcohol and acid8:1, dosages of catalyst 2%, reaction time 120min and reaction temperature 70℃.The process of stage pre-esterification can carry off some water from methanol. The effect of dehydration is obvious. The reaction time is shortened 1h and the percent recovery of catalyst is 90%more by the stage esterification.The influence of acid value (AV) of oil on transesterification was investigated. The results show that the AV of oil could not be more than 4mg/g.The study showed that the longer carbonchain of fatty acid methyl ester and the more saturation fatty acid methyl ester,the worse low temperature property of biodiesel.we can improve the low temperature property of biodiesel by freezing and filtering,blending with diesel and adding epoxy fatty acid methylester.This paper also studied on refining glycerine from the by-product of biodiesel. The effect of kind of acid solution, pH, solvent, dosages of solvent, reaction time and reaction temperature on acid treatment was investigated. The optimum acidification conditions are as follow:50% sulfuric acid 11g, water as solvent 20g, reaction time 20min, reaction temperature 60℃.Under this condition, the percent recovery of glycerine is 98.3%. The effect of pH on percent recovery of glycerine in alkali treatment was investigated. The result shows that pH=7 is the best. The percent recovery of glycerine is 96.3%.Under this condition, the glycerine polymerizes rarely and the remainder of distillation is least. The fatty acid of distilled glycerine is low level. The content of distilled glycerine is 97.43%.The content of rectified glycerine 98.93%.Analyzed by GC-MS, the rectified glycerine has single peak. It shows that the rectified glycerine contains few organo-impurity. The distilled glycerine and rectified glycerine is decolored by acticarbon. The effect of dosage of acticarbon on decoloring was investigated. The result shows that the light transmittance arrives at 99.8%. The content of decolored glycerine is 99.12%.