Study On Preparation Of Biodiesel From Sorbifolia Oil Catalyzed By Modified Mesoporous Molecular Sieves

With the rapid development of world economy, the demand and consumption of energy become increasingly pronounced. However, the exhausting petroleum resource and soaring oil prices make the energy form as petroleum cracking faced severe challenges. And the same time, the excessive consumption of fossil energy greatly destroys the natural environment and seriously threatens the human living space. So searching alternative resources and energy industry is imperative. As a renewable alternative energy sources, biodiesel had already applied and popularized in many countries. The preparation of biodiesel mainly uses transesterification. Present used catalysts are homogeneous acid or alkali, but saponification reaction easily happens and separation between products and catalysts are difficult in homogeneous catalysis. Heterogeneous catalysis can largely overcome the disadvantages in homogeneous catalysis. Therefore, research workers focus on the development in new heterogeneous catalysts (namely solid catalyst) for the preparation of biodiesel.Mesoporous molecular sieves is an excellent catalyst carrier, which possesses highly ordered mesoporous pore structure, high specific surface area, larger pore size and tenability compared with other porous materials. Mesoporous material as a carrier, using its large surface area and stabile structure can improve the catalytic performance. Therefore, this article used mesoporous SBA-15 and MCM-41 as the carriers, prepared solid base catalysts by loading inorganic potassium salts or organic base on them; then solid base catalysts catalyzed sorbifolia oil to produce biodiesel by transesterification, and biodiesel yield was an activity index of solid alkali catalyst.Research in the paper included:(1) The supported solid base catalysts were obtained, which were used the mesoporous molecular sieves SBA-15 and MCM-41 as carriers, and loaded Al and Mg,then coated potassium salt or organic base on it. (2) The solid base catalysts were characterized by XRD, SEM, BET and CO2-TPD; (3) The preparation conditions of supported solid base catalysts were optimized by single factor experiment; (4) Solid base catalysts catalyzed sorbifolia oil to produce biodiesel by transesterification, and biodiesel yield was an activity index of solid alkali catalyst;(5) The crude biodiesel produced by transesterification was purified and analysed by column chromatography.The main conclusions as following:1) The mesoporous molecular sieves SBA-15 and MCM-41 as carriers loaded Al or Mg by direct synthesis and post synthesis method. The mesoporous molecular sieves after loading were dipped in alkaline metal salt solution or organic base 3-aminopropyl triethoxysilane (APTS). The supported solid base catalysts were finally obtained by being dried and calcined. Among the catalysts, KNO3-Al-SBA-15 had the highest catalytic activity after the activity evaluation;2) Characterization of XRD, SEM, BET, CO2-TPD and other means showed that the addition of Al or Mg played a role in alkaline erosion to protect the pore structure of SBA-15 and MCM-41 zeolite. Loading APTS and KNO3 in molecular sieves can significantly increase the alkaline of them;3) Taking the KNO3-Al-SBA-15 possessing the highest activity as example, we will discuss the single factor experiments of catalyst preparation. The optimum preparation conditions were KNO3 loading about 17%, calcination temperature about 550℃, calcination time about 6h;4) The activity of the catalysts was evaluated by yield of biodiesel prepared by transesterification. Transesterification conditions were reaction temperature about 70℃, molar ratio of methanol to oil about 12:1, catalyst amount about 5%, ultrasound power about 300W. Under these conditions, the catalyst activity of KNO3-Al-SBA-15 is better than other solid base catalysts. The yield of biodiesel by transesterification can reach about 92%. Although the catalyst was reused five times, the yield of biodiesel was still able to reach 64.8%, which indicated that the prepared catalyst possessed good reusability;5) The eluent of column chromatography was the mixture of petroleum ether and methanol, adopting the way of gradient elution. The refined biodiesel was analyzed by gas chromatographic. The results showed the purity of biodiesel was up to 93.87% and the recovery of column chromatography products was about 91.04%. The refined biodiesel were further analyzed by IR and NMR spectroscopy. IR results indicated that impurities of biodiesel refined by column chromatography significantly reduced. The results showed that column chromatography was a good method to refine the biodiesel.