Controlled Synthesis Of Magnetite Nanoparticles Within A Supramolecular Organogel Network And Its Application In Catalysis Of Biodiesel Preparation

Magnetic nanoparticles, especially magnetite （Fe₃O₄）, have attracted tremendousattention due to their potential applications in magnetic fluid, magnetic recordingmedia, catalysts, biomedical fields and so on. In this paper, magnetite nanoparticleswith high crystallinity and saturation magnetization were facilely constructed at roomtemperature by using GP-1/PG supramolecular organogel fiber network as a template.Moreover, a magnetic composite solid catalyst was developed by loading calciumaluminate onto Fe₃O₄nanoparticles for transesterification reaction of biodieselproduction.Firstly, the processes of nanoparticles synthesized in aqueous solution and GP-1/PGsupramolecular organogel fiber network were repectively investigated in comparison.The results show that organogel-templating method has remarkable advantages in thepropertites of the synthesized Fe₃O₄nanoparticles including morphology, crystallinephase and magnetism compared with co-precipitation method in aqueous solution.On this basis, the effects of kind and concentration of the precipitator, gelatorconcentration, and reaction time on the morphology, crystalline phase, and magneticperformance of Fe₃O₄nanoparticles were studied. X-ray diffraction （XRD）,transmission electron microscopy （TEM） and vibrating sample magnetometer （VSM）were used to characterize the synthesized nanoparticles. It was found that themorphology and crystalline phase of nanoparticle strongly depend on the kind andconcentration of the precipitator. The suitable precipitator is7.5mol/L NaOH and thesuitable gelator concentration is5wt%. The morphology and magnetism of Fe₃O₄nanoparticles have almost no changes with the extension of the reaction time, whichshows the excellent sealing ability of gel template. Furthermore, the growth curve ofFe₃O₄nanoparticles was investigated. The growth rate is higher and crystal growthbalance time is shorter in GP-1/PG fiber network than those in aqueous phase.Using commercial Fe₃O₄as the material, a magnetic composite solid catalyst wasdeveloped by loading calcium aluminate onto Fe₃O₄nanoparticles via a chemicalsynthesis method and used for transesterification reaction of biodiesel production. Theoptimum conditions for the catalyst preparation were investigated. The influences ofthe molar ratio of Ca to Fe, calcining temperature, calcining time on the catalytic performance were studied. The catalyst with the highest activity can be obtained whenthe molar ratio of Ca to Fe is5:1; calcining temperature is600℃and calcining timeis6h. The catalyst was characterized by X-ray diffraction （XRD）, scanning electronicmicroscope （SEM）, Brunauer–Emmett–Teller method （BET） and vibrating samplemagnetometer （VSM）. Furthermore, the magnetic composite solid catalyst shows highcatalytic activity for transesterification reaction of biodiesel preparation and the yieldof fatty acid methyl ester （FAME） reaches98.71%and the recovery rate of thecatalyst is93.80%under the optimum reaction conditions. This catalyst showsmagnetism and can be easily separated by an external magnet. After5-times use ofCa/Al/Fe₃O₄magnetic composite catalyst, the FAME yield reaches above93%. Boththe catalytic activity and the recovery rate of the magnetic composite solid catalyst aremuch higher than those of pure calcium aluminate catalyst. Using the selfmade Fe₃O₄nanoparticles as the material, the prepared Ca/Al/Fe₃O₄magnetic composite catalystalso shows high catalytic activity for transesterification reaction of biodieselproduction and the FAME yield reaches98.85%and the recovery rate of the catalystis94.47%under the lower catalyst dosage, which are higher than those with themagnetic catalyst prepared from commericial Fe₃O₄nanoparticles. It fully suggeststhe advantages of supramolecular organogel fiber network as a template to synthesizenanomaterials.