Synthesis And Characterization Of Solid Base Catalyst And Its Application In The Biodiesel Production From Waste Cooking Oil

With the rapid depletion of fossil energy and the serious environmental pollution problemscaused by the use of fossil energy, it is very necessary to develop and utilize environment-friendlyrenewable energy. Biodiesel is recognized as a promising substitute for fossil diesel due to itsrenewable nature, environmentally beneficial attribute, high safety, excellent using performanceand high compatibility. Moreover, every year in China, a large amount of waste cooking oil isproduced, which not only pollutes the environment, but also endangers people’s health. If thewaste cooking oil could be transformed into biodiesel, then it would eliminate the harm of wastecooking oil and supply adequate feedstock for the biodiesel production. Therefore, in this thesis,purchased waste cooking oil was first purified and used as the feedstock to produce biodiesel.Through the transesterification of the refined waste cooking oil into biodiesel over the preparedzinc and lanthanum solid base and Ca/SBA-15solid base, respectively, both the optimum solidbase catalyst preparation conditions and the optimum transesterification reaction conditons wereinvestigated, the relative physicochemical properties of the optimum catalyst were characterized,and the reutilization performance of the optimum catalyst was studied. The composition of theproduced biodiesel was analyzed and the biodiesel field was calculated.(1) The zinc and lanthanum solid base catalyst was prepared by means of thecoprecipitation method with ammonium oxalate as the precipitant, used in the transesterificationinto biodiesel and characterized by TG-DTA, X-ray diffraction (XRD), inductively coupledplasma atomic emission spectroscopy (ICP-AES) and scanning electron microscopy (SEM). Theresult shows that the catalyst with3:1molar ratio of zinc to lanthanum, calcined at700℃exhibits the optimum catalytic activity, which is composed of ZnO and La2O3with the particle sizeof approximate100nm. The biodiesel field can reach91.6wt.%under the optimum conditions ofa methanol/oil molar ratio of36:1, a catalyst amount of5wt.%(referred to oil), a reactiontemperature of200℃and a reaction time of3h. Although the optimum catalyst still has the leaching problem, the biodiesel field can remain above80wt.%after the fourth circle.(2) The Ca/SBA-15solid base catalyst was prepared through the sol-gel method, usingtetraethyl orthosilicate as the silicon source, lime acetate as the calcium source and P123as thestructure-directing agent, used in the transesterification into biodiesel and characterized by X-raydiffraction (XRD), fourier transform-infrared (FT-IR) spectroscopy, transmission electronmicroscope (TEM) and N2adsorption-desorption analysis. The result shows that the catalyst withCa/Si molar ratio of0.2, calcined at700℃exhibits the optimum catalytic activity, which canwell maintain the original two-dimensional p6mm hexagonal order mesoporous structure and havea BET surface area of406.7m2g-1. The biodiesel field can reach94.7wt.%under the optimumreaction conditions of a methanol/oil molar ratio of12:1, a catalyst amount of5wt.%(referred tooil), a reaction temperature of65℃and a reaction time of7h in the N2atmosphere. Washed anddried, the catalyst can be directly reutilized in the next circle without reactivation. After the fifthcircle, the catalytic activity decreases but the biodiesel yield is still above86wt.%.(3) The biodiesel produced by the optimum solid base catalyst was analyazed through thegas chromatograph-mass spectrometer (GC-MS). The result shows that the composition of thebiodiesel produced by the optimum zinc and lanthanum solid base catalyst is very similar to thatproduced by the optimum Ca/SBA-15solid base catalyst and the percentages of the unsaturatedfatty acid methyl esters in the2kinds of biodiesels are74.0wt.%and70.5wt.%, respectively.Both of the biodiesels contain9kinds of fatty acid methyl esters, which are oleic acid methyl ester,linoleic acid methyl ester, palmitic acid methyl ester, stearic acid methyl ester, linolenic acidmethyl ester, palmitoleic acid methyl ester,11-eicosenoic acid methyl ester, myristic acid methylester and arachidic acid methyl ester in descending order according to the content.