合成酵素固定或化學酸官能化磁性中孔洞氧化矽奈米粒子做為可回收式固體催化劑應用於纖維素-葡萄糖-果糖-5-羥甲基糠醛序列式生質轉換

Abstract

This study focuses on the synthesis of magnetic mesoporous silica nanoparticles (MSN). We obtained two recyclable catalysts by utilizing magnetic mesoporous silica nanoparticles to immobilize two types of enzymes (cellulase and isomerase). Furthermore, we functionalized mesoporous silica nanoparticles with sulfonic groups by a grafting method. By utilizing these three kinds of solid recyclable catalysts, we successfully converted cellulose to 5-hydroxymethylfurfural (HMF) in a bi-phase system via a sequential reaction. First, because of the expensive price of enzymes, we tried to immobilize cellulase or isomerase on Fe3O4@MSN and recycle these catalysts using magnetic force. Second, we utilized mesoporous silica nanoparticles with many hydroxyl groups to functionalize them with sulfonic groups. We chose silane with thiol functional groups, and after performing a condensation reaction between the materials and silane, we oxidized the thiol groups to sulfonic groups. We could obtain acidic solid catalysts. Then we characterized functionalized the MSN by solid-state NMR to quantify how many sulfonic functional groups had been connected onto the solid materials. Finally, we utilized these three types of recyclable solid catalysts to conduct cellulosic bioconversion. We used pretreated cellulose as the reactant and immobilized cellulase on Fe3O4@MSN as the catalyst to hydrolyze cellulose to glucose. Then after recycling the solid catalysts using magnetic force and changing the buffer pH value, we added immobilized isomerase on Fe3O4@MSN as a catalyst to isomerize glucose to fructose. Finally, after recycling the recycle solid catalysts using magnetic force and adding an organic phase (DMSO), we added functionalized MSN (with sulfonic groups) as a catalyst to dehydrate fructose to HMF. This step-by-step reaction was called a sequential reaction. The advantage of this sequential reaction is that we can optimize the reaction conditions of each step, obtain high product yields, and lower the production of by-products. By utilizing this sequential reaction, we were able to obtain a high yield of the final product. The HPLC results showed that the highest yield of HMF converted from fructose, glucose and pretreated cellulose were 81.3%, 46.1%, and 45.6%, respectively in the presence of the three solid catalysts. This is the first report on the generation of HMF from fructose, glucose, and pretreated cellulose via a sequential reaction with immobilized enzymes on magnetic mesoporous silica nanoparticles that are grafted with sulfonic groups.