The Study Of Preparing Biodiesel From Acidified Soybean Oil

With the lack of oil resources day by day and the enhancement of people's environmental awareness, people start to seek for one kind of renewable new energy to reduce environmental disruption and replace petroleum fuel. People pay much more attention to biodisel due to its some merits such as its renewability and harmonization with enviroment. Taking acidified oil as raw material to produce biodiesel can not only cut down the current high raw material prices of biodiesel, but also well deal with the problem of environmental pollution which aroused by mishandled of oil foot generated from vegetable oil refining factory, which has good economic returns and social benefits. Therefore, using the acidified oil to synthesize biodiesel has important research significance.The experiment adopted the process including concentrated sulfuric acid catalytic pre-esterification, concentrated sulfuric acid catalytic esterification and sodium hydroxide catalytic transesterification reaction. First, most fatty acids in acidified oil took part in the pre-esterification reaction, then steam out the water generated from the reaction. Next, through the esterification reaction the acid value reduce to 2.0 below, reaching the demand of raw material of alkali catalytic transesterification reaction, and then carries on transesterification reaction. Finally obtained biodiesel products through the reduced pressure distillation. Comparing with traditional a step esterification craft, this experiment could significantly reduce alcohol-oil ratio, greatly shorten the esterification reaction time through the pre-esterification and the esterification. Comparing with only acid catalytic esterification, the alkali catalytic transesterification can increase the rate of conversion of triglyceride in acidified oil greatly, and raise yield of biodiesel by more than ten percent points.Each reaction in the experiment, taking methanol/oil mole ratio, reaction time, reaction temperature and catalyst dosage as the inspection factor, has carried on the single factor experiment and the orthogonal experiment respectively. The obtaining optimum operating conditions as follows:(1)The optimum operating condition of acid catalytic pre-esterification is: methanol/oil mole ratio 16, reaction time 8h, reaction temperature 70℃, catalyst dosage 2%. Under these conditions, the acid value of the acidified oil falls from 128 to 5.6, and esterification rate reachs 95.6%.(2)The optimum operating condition of acid catalytic esterification is: methanol/oil mole ratio 12, reaction time 5h, reaction temperature 70℃, catalyst dosage 2%. Under these conditions, the acid value of the acidified oil falls from 5.6 to 1.9, and esterification rate reachs 98.5%.(3)The optimum operating condition of alkali catalytic transesterification is: methanol/oil mole ratio 6, reaction time 1h, reaction temperature 60℃, catalyst dosage 1%. Under these conditions, finally through the reduced pressure distillation, collect distillates under the temperature of 160-240℃and the pressure of 1.33kPa. The biodiesel's ultimate yield reaches 80.2%.Carring on the qualitative analysis to the biodiesel using the gas chromatography, the chemical composition of biodiesel was definited. The boiling range, condensation point, flash point, viscosity and the sheet copper corrosion were measured, and was carried on the contrast with the domestic and foreign biodiesel production standard. The product quality has met target requirement. The experimental result confirmed the feasibility of biodiesel replace partly 0# diesel.In this paper, using chemical process simulation software Aspen Plus to carry on analog computation of biodiesel process units of output of 10,000 tons annually, has ascertained operation parameters of the main equipments, and has certain guiding significance to realizing industrialization production.