Preparation,Modification And Application Of Magnetic Carbon Microspheres

In recent years,carbon microspheres have been used as a new type of carbon material in the fields of catalysis and adsorption and gradually developed into scientific research hotspot.Carbon microspheres have characteristics of regular spherical structure,stable chemical properties,good heat resistance and fluid fluidity,and are considered to be catalyst supports and precursors of adsorbents with competitive advantages and good market prospects.In this dissertation,the magnetic carbon microspheres were prepared by a hydrothermal method with Fe₃O₄ as the magnetic agent and glucose as carbon source.The magnetic carbon microspheres were acid-modified and alkali-modified with concentrated sulfuric acid and KOH respectively to prepare solid acid catalysts and carbon microsphere adsorbents with a characteristic of magnetic responsiveness.Solid acid catalysts and carbon microsphere adsorbents are not only used in the fields of catalysis and adsorption,but also can be rapidly and efficiently separated and recovered by magnetic separation technology.The main research contents are as follows:?1?Fe₃O₄ and glucose were used as the magnetic agent and carbon source,respectively.Magnetic carbon microspheres with good dispersibility,uniform particle size and magnetic responsiveness were prepared when the concentration of glucose was0.3 mol/L,hydrothermal temperature was 190 ^oC and hydrothermal time was 4 h.?2?The magnetic carbon microspheres were sulfonated with concentrated sulfuric acid.The acid density of the catalyst was 2.84 mmol/g and the saturation magnetization was 4.25 emu/g when the amount of concentrated sulfuric acid was 15 mL,sulfonation temperature was 120 ^oC and sulfonation time was 8 h.The catalysts had a good catalytic performance in the esterification reaction of oleic acid and methanol,the esterification rate of oleic acid reached 89.43%when the amount of catalyst was 7.5%of oleic acid,molar ratio of methanol to oleic acid was 24:1,esterification temperature was 90 ^oC and esterification time was 3 h.In addition,the catalysts had a good reusability,thermal stability and certain magnetic responsiveness.?3?The magnetic carbon microspheres were activated and pored by KOH to improve their adsorption performance.With the increase of KOH concentration,activation temperature and activation time,the yield of magnetic carbon microsphere adsorbents gradually decreased,and the adsorption performance of methylene blue increased first and then decreased.Adsorbents had the best adsorption performance when the concentration of KOH was 30%,activation temperature was 850 ^oC and activation time was 60 min.The specific surface area,pore volume and micropore porosity of adsorbent were 793.55 m²/g,0.51 m³/g and 62.75%,respectively.The saturation magnetization of adsorbents reached 10.61 emu/g and adsorbents could be quickly separated from the adsorption system under the action of an external magnetic field.Adsorption of methylene blue on adsorbents was consistent with the pseudo-second-order kinetics model.The methylene blue adsorption capacity of adsorbents reached 354.78 mg/g when the concentration of methylene blue was 200 mg/L,dosage of adsorbent was 0.02 g,adsorption temperature was 55�C,adsorption time was 60 min and pH was 11.