Abstract:

Fe₃O₄/C-SO₃H（A） and Fe₃O₄/C-SO₃H（B） were magnetic carbon-based solid acid catalysts. Fe₃O₄/C-SO₃H（A） was synthesized by step-by-step method. Fe₃O₄/C-SO₃H（B） was synthesized by one-step method. They were prepared by ferric oxide, biomass carbon and sulfonic acid source. Ferric oxide was the magnetic core, while soluble starch was the matrix, and p-toluenesulfonic acid was the source of sulfonic acid group. The structure of the catalysts was characterized by SEM, XRD,FT-IR, TG and Vibrating Sample Magnetometer （VSM）. The synthesis of octyl glucoside was used as a probe. The activity of the catalyst was measured by the conversion of glucose and catalyst acid content. The activity of two catalysts was compared, the catalyst with good activity was applied to the synthesis of octyl glucoside, and the synthesis conditions of octyl glucoside were optimized. The optimization factors were investigated, such as the amount of catalyst, the mole ratio of octanol to glucose, the reaction temperature, the structure of octyl glucoside and the repeatability of catalyst. The results show that the crystal structure of Fe₃O₄ magnetic particles has not changed significantly after carbonization and sulfonation. Fe₃O₄ magnetic particles still retain good magnetic properties, and can be quickly separated from the system under the action of external magnetic field. Catalyst Fe₃O₄/C-SO₃H（A） is a core-shell structure with a particle size of about 30 nm. Fe₃O₄/C-SO₃H（B） is amorphous particles with porous structure. Both catalysts have good thermal stability and magnetic properties. The acid content of Fe₃O₄/C-SO₃H（A） is 1.17 mmol/g, and the glucose conversion rate in the probe reaction is 97.9%. The acid content of Fe₃O₄/C-SO₃H（B） is 0.91 mmol/g, and the glucose conversion rate in the probe reaction is 95.4%. Compared with Fe₃O₄/C-SO₃H （B）, Fe₃O₄/C-SO₃H （A） has better performance in acid content, and glucose conversion. Therefore, Fe₃O₄/C-SO₃H（A） is selected as the catalyst for the synthesis of octyl glucoside. Fe₃O₄/C-SO₃H（A） is used for octyl glucoside process optimization. When the amount of Fe₃O₄/C-SO₃H（A） is 7% （w/%） of glucose, the molar ratio of n-octanol to glucose is 9 to 1, and the reaction temperature is 140 ℃, the conversion rate of glucose can reach 98.5%. The catalyst can be reused by simple magnetic field separation. After repeated using 3 times, the conversion rate of the glucose reaches more than 92%.

Key words: magnetic catalyst, solid acid catalyst, structural characterization, octyl glucoside, repeated use