磁性碳基固体酸制备及其在糖苷合成中的应用研究

Study on preparation method of magnetic carbon-based solid acid and its application in glycoside synthesis

以四氧化三铁为磁核,可溶性淀粉为基质,对甲苯磺酸为磺酸基来源,分别采用分步法和一步法制得磁性碳基固体酸催化剂Fe_(3)O_(4)/C-SO_(3)H(A)和Fe_(3)O_(4)/C-SO_(3)H(B)。利用SEM、XRD、FT-IR、TG、振动样品磁强计(简称VSM)等手段对催化剂进行表征,并将两种催化剂的活性进行比较,活性好的催化剂应用于辛基葡萄糖苷的合成。结果发现,Fe_(3)O_(4)/C-SO_(3)H(A)为核壳结构,粒径大小约为30 nm;Fe_(3)O_(4)/C-SO_(3)H(B)表现为具有一定多孔结构的无定形颗粒物;两种催化剂均具有较好的热稳定性和磁学性能。相比于Fe_(3)O_(4)/C-SO_(3)H(B),Fe_(3)O_(4)/C-SO_(3)H(A)在酸含量、葡萄糖转化率上表现更佳,因此选用Fe_(3)O_(4)/C-SO_(3)H(A)作为辛基葡萄糖苷的合成催化剂。当Fe_(3)O_(4)/C-SO_(3)H(A)用量为葡萄糖质量7%,正辛醇和葡萄糖的摩尔比为9∶1,反应温度为140℃时,葡萄糖转化率可达到98.5%。催化剂可通过简单的磁场分离进行重复利用,重复使用3次后,葡萄糖的转化率仍在92%以上。

Fe_(3)O_(4)/C-SO_(3)H(A) and Fe_(3)O_(4)/C-SO_(3)H(B) were magnetic carbon-based solid acid catalysts. Fe_(3)O_(4)/C-SO_(3)H(A) was synthesized by step-bystep method. Fe_(3)O_(4)/C-SO_(3)H(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 Fe_(3)O_(4)magnetic particles has not changed significantly after carbonization and sulfonation. Fe_(3)O_(4)magnetic particles still retain good magnetic properties, and can be quickly separated from the system under the action of external magnetic field. Catalyst Fe_(3)O_(4)/C-SO_(3)H(A) is a core-shell structure with a particle size of about 30 nm. Fe_(3)O_(4)/C-SO_(3)H(B) is amorphous particles with porous structure. Both catalysts have good thermal stability and magnetic properties. The acid content of Fe_(3)O_(4)/C-SO_(3)H(A) is 1.17 mmol/g, and the glucose conversion rate in the probe reaction is 97.9%. The acid content of Fe_(3)O_(4)/C-SO_(3)H(B) is 0.91 mmol/g, and the glucose conversion rate in the probe reaction is 95.4%. Compared with Fe_(3)O_(4)/C-SO_(3)H( B), Fe_(3)O_(4)/C-SO_(3)H( A) has better performance in acid content, and glucose conversion. Therefore, Fe_(3)O_(4)/C-SO_(3)H(A) is selected as the catalyst for the synthesis of octyl glucoside. Fe_(3)O_(4)/C-SO_(3)H(A) is used for octyl glucoside process optimization. When the amount of Fe_(3)O_(4)/C-SO_(3)H(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%.