Study On Biodiesel Preparation By Solid Acid Catalyst

Due to the double pressures that petroleum resource is drying up gradually and environmental pollution is becoming badly day by day, correlative experts and scholars around the world are positively researching on reproducible and green energy. Especially, it is China that has been short of petroleum resource, and along with the high-speed development of Chinese economy after reform and open to the outside world, the degree of mechanization in the industry and agriculture has been advanced greatly, motor vehicle has been increased hugely, so the requirement of diesel oil has being risen in China. Now, China is the second petroleum importer and consumer in the world. In order to decrease the degree of depending on petroleum export country, and ensure the healthy and speedy development of our national economy, lots of documents and correlative laws have been promulgated which support the development of green and regenerative energy. As an important form of biological fuel, biodiesel oil with its particular merits has been accepted by experts and scholars from home and abroad. But the excessive cost of material and the pollution of wasted liquid have seriously restricted the speedy development of biodiesel. Aiming at deficiencies hereinbefore, this paper researches the production technology of biodiesel by two steps, which uses solid superacid as catalyst and use wasted oil as material. The main conclusions were:1. After the pretreatment of deguming, dehydration and decolor, the wasted oil contained phosphatide 0.11%, impurity 0.067%, water and volatile substance 0.26%, the color of pretreated oil became lighter, the rate of deguming reached 31.2%, the saponification value was 229.6mgKOH/g, the acid value was 31.9mgKOH/g. Each index could basically meet the requirement of material oil in the process of the practice production, and according to the acid value, the production technology that the esterification with acid must be done before the transesterification was ascertained.2. The conversion ratio of free fat acid in the wasted oil acted as study index, when solid superacid acted as catalyst to accelerate the esterification between free fat acid and methanol. When the ratio of molor of methanol to the wasted oil was 15:1, the dosage of the catalyst was 3% of the quantity of the wasted oil, the reaction was lasted for two hours at 70℃. In this way, the effect that the different conditions of the preparation which acted on the activity of the catalyst was studied. The result of the experiment indicated:(1) First the solid mixture with 22.5% of SnO₂ was dipped in the 1.0mol/L sulphoacid which dissolved 3% La₂O₃ at the proportion of 25mL/g for a period of time at a certein temperature, and then the obtained filtrate was calcinated for three hours at 550℃, the activity of the solid superacid catalyst obtained in this way is the highest.(2) Among those complex solid superacid catalysts, whose carriers were ZrO₂ or TiO₂ which were made in the best condition, the activity of the catalyst of SO₄^2-/SnO₂-TiO₂-ZrO₂- La₂O₃(A) was the best, the esterification ratio of the free fat acid was 89.5%, it was better than what we have known.3.The acid strength of the solid superacid was measured by the method of Hammett indicator, the type of activity center was analyzed by means of IR spectrum, the state of the existence and the type of the compound in the solid superacid made in different conditions were determined by the method of XRD patterns, the conclusion was: The percent of oxid mixture, the calcination temperature, the concentration and dosage of sulphoacid solution, the former state of calcination, and the species and dosage of Lanthanon could affect the acid strength, the amount and distribution of acid center, specific surface area, the sort and existing state of compound in the solid acid.4.On the basis of analyzing that the four elements of the dynamics, the reaction temperature, the reaction time, the molor ratio of methanol-to-oil and the dosage of catalyst, impacted on the ratio of the esterification, the notable sequence and the best reaction condition that the four elements of dynamics which impacted on the ratio of esterification were obtained by the method of orthogonal experiments. Then the situation of the reuse of solid superacid made by myself was tested. The result of the emperiment indicated:(1)These four elements of dynamics had visible effect on the ratio of esterification, the visible sequence was: the reaction time>the reaction temperature >the dosage of the catalyst >the molor ratio of methanol-to-oil;(2)The optimum condition of reaction:the molor ratio of methanol-to-oil is 15:1, the dosage of the catalyst is 3%, the reaction temperature is 70℃, the reaction time is 6h, in this condition the ratio of esterification is 95.4%. Through comparison, the activity of the solid superacid catalyst made by myself is better than sulphoacid. After the esterification, the acid value of the oil is lower evidently, so the next technique can be catalyzed either by acid or by alkali, and can not be confined by productive technique.(3)The solid superacid made by myself has perfect reuse effect, although it had been used five times, the activity of catalyst only reduced 10.3%.5.On the basis of respectively analyzing that the single element of the four dynamics elements impacted on the ratio of the transesterification, the notable sequence and the best reaction condition that reaction temperature, the molor ratio of methanol-to-oil, the reaction time, the dosage of the catalyst impacted on the ratio of the transesterification.The main components of the biodiesel made by myself were analysed by the means of gas chromatography, the physical and the chemical property of the biodiesel were simply characterized. The result of the emperiment was:(1)The visible sequence of these four factors of dynamics which had visible effect on the ratio of transesterification was: the reaction temperature>the dosage of the catalyst> the molor ratio of methanol-to-oil >the reaction time.(2)The optimum condition of reaction: the molor ratio of methanol to the wasted oil is 6:1, the dosage of the catalyst is 3%, the temperature of reaction is 75℃, the time of reaction is 7h, in this condition the ratio of transesterification is 96.7%.(3)The elements contained in the production of the biodiesel are complex, the total contents of methyl ester come to 98.59%, and aromatic hydrocarbon is not contained.(4)The physical and chemical capabilities of the biodisel production such as kinematic viscosity, flash point, the content of the sulphur, the value of acid, cetane ratio and the content of glycerin all reach the American standard(D6751-03a), and it has a certain practice productive value.