Preparation Of Carbon Based Solid Acid Catalyst From Microalgae Residue For Biodiesel Production

As biomass resource possesses extensive sources and renewable characteristics,development and utilization of biomass resources to address energy and environmentalissues have become an important issue in today’s world. Biodiesel has the advantage ofrecycling and similar physical and chemical properties with petroleum diesel, and friendlyto the environment, which is considerated to be the best choice to substitute for petroleumdiesel. In order to overcome the homogeneous acid-base catalysis’ drawbacks, such as highrequirement of biodiesel feedstock, difficulty in separation from the product, resulting inenvironmental pollution, and to achieve green biodiesel production, this thesis successfullydeveloped two types of carbon based solid acid catalysts. One was prepared by in situcarbonization and sulfonation of microalgae with sulfuric acid in single-step reaction, theother one was prepared from microalgae by chemical activation with phosphoric acid,pyrolysis and sulfuric acid. The elemental composition and structure of the above preparedcatalysts were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope(SEM), Brunauer, Emmett, and Teller (BET) method analyses (BET), Elemental Analysis(EA) and Acid-base titration. They were further applied for biodiesel production from fatraw materials.In this study，the performance of carbon based solid acid by single-step showed thatthe concentration of sulfuric acid, the carbonization temperature and carbonization timewere significant influence on the catalytic activity of prepared catalysts, wherein thesulfuric acid concentration affected most. The carbon based solid acid with the highestcatalytic activity could be obtained under the following optimal reaction conditions:optimal carbonization temperature and time was180℃and2h. The prpared catalyst hasthe highest acid strength and the best catalytic performance. About98%conversion of theesterification reaction and24%yield of transesterification reaction in12h were achieved.The yield of transesterification reaction in a sealed autoclave for12h was99.5%. Whileabout85.77%conversion of the esterification reaction and8.30%yield of transesterification reaction catalyzed by Amberylyst-15in12h were achieved. When thecatalyst was reused, the catalyst activity decreased gradually, but its activity can berecovered by filtration after bath experiment with concentrated sulfuric acid and thenwashed with the hot water.In addition, the performance of carbon based solid acid prepared from microalgae bychemical activation showed that various parameters affects the catalytic activity. Theoptimal preparation conditions was as followed: the ration of microalgae residue and30%phosphoric acid was1:6(wt/vol), optimal carbonization temperature and time was250℃and2h, suitable sulfonation temperature and sulfonated time was90℃and12h. About99.80%yield of transesterification reaction in a sealed autoclave under120℃for12h wereachieved. The carbon based solid acid catalyst could be reused for six times and thecatalytic activity almost remained unchanged, which shows that the catalyst has goodstability.In this study, carbon based solid acid catalysts with excellent catalytic activity havebeen successfully developed from microalgae residue, which not only reduce theproduction cost of biodiesel, but also realize the resource utilization of waste and reduceenvironmental pollution. This study is of practice significance and industrial applications.