Preparation Of Solid Superacid And Catalytic Synthesis Of Fatty Acid Methyl Esters From Waste Oil

Sulfated zirconia?referred to as SZ?solid super acid catalyst has super strong acid and high catalytic activity,which has become a research hotspot.However,the traditional SZ has a small specific surface area,and the pore structure is not uniformly distributed,which limits its potential applications.In this thesis,two kinds of ordered mesoporous molecular formulas were prepared as SO₄^2-/ZrO₂?S₂O₈^2-/ZrO₂-SiO₂ and a nano S₂O₈^2-/ZrO₂ super acid catalyst,which were applied to the transesterification reaction of frying waste oil.The specific research contents are as follows:?1?A series of ordered mesoporous sulfated zirconia?OMSZ?with different calcination temperatures?400-650??have been synthesized by self-assembly method using zirconium n-propoxide as raw material,P123(EO₂₀PO₇₀EO₂₀)as structure-directing agent and ammonium sulfate as sulfonating agent.The transmission electron microscopy?TEM?results indicated that the OMSZ had the ordered mesoporous structure and the X-ray diffraction?XRD?analysis further revealed that the OMSZ had hexagonal ordering structure.The N₂-BET results showed the OMSZ were mesoporous materials?2.7-5.0 nm?and when the calcination temperature was 500?,the BET surface area could reach 183 m²/g.NH₃-TPD programmed temperature desorption curves confirmed that the OMSZ possessed superacid when the calcination temperature was higher than 450?.The catalytic activity of OMSZ was observed for transesterification of waste frying oil,and 92%of yield could be obtained after 6 h at 200?.?2?A series of ordered mesoporous S₂O₈^2-/ZrO₂-SiO₂?OMSZS?solid superacids with different calcination temperatures?400?-650??was synthesized using zirconium n-propoxide and tetraethyl orthosilicate as the raw materials and P123 as a structure-directing agent by solvent evaporation-post-dipping method.Transmission electron microscopy and small-angle X-ray diffraction results showed that the OMSZS were all ordered.The nitrogen adsorption results indicated that the specific surface area of OMSZS could reach up to 331-385 m²/g,whereas the average pore diameters were in the range of 3.1-3.2 nm.The pyridine infrared results mainly displayed Lewis acids,and the ammonia?NH₃-TPD?temperature programmed desorption characterization showed that the NH₃ desorption of the OMSZS calcined at550?was 61 cm³/g STP.The catalytic performance of the OMSZS was investigated by the transesterification reaction of waste frying oil and methanol.The yield of fatty acid methyl ester could reach up to 94%at 200?reaction temperature for 6 h.After repeated use for four times,the catalyst still featured good activity and the yield was78%.?3?A solid super acid catalyst with nanometer particle size was prepared by solvothermal synthesis-post-precipitation impregnation method.The NH₃-TPD chemical desorption curve was used to prove that the catalyst formed a strong acid site.N₂ adsorption-desorption indicates that the NSZ catalyst has a specific surface area of 242 m²/g at 400?with increasing surface area with increasing temperature.Wide-angle XRD indicates that the catalyst still maintains a high tetragonal phase at600?and a small part of the tetragonal phase is transformed into oblique phase.The TEM characterization indicated that the synthesized catalyst was nano structured and its catalyst was applied to the transesterification of waste oil with methanol.The catalytic performance under different conditions was investigated.