Design And Synthesis Of Solid Acid Catalyst And Its Application In Organic Synthesis Of Water Media

Homogeneous acid catalysts are mostly common used in the large-scale production of industrial chemicals and fine chemicals. However, their inherent drawbacks such as the corrosivity, the environmental hazards as well as the high cost of separating the acids from the reaction system, make it very difficult to meet the requirements of environmentally friendly chemical processes. Moreover, some of them generally must be used under anhydrous conditions, which necessitates massive toxic, flammable organic solvents and specialized reaction vessels. Importantly, organic reactions carried out in water medium have become a new trend of green chemistry since water is the most innocuous substance on Earth and therefore the safest solvent possible. The remarkable advantages of solid acid system in water are that it could simultaneously reduce the pollution and cost resulting from liquid acids and organic solvents, coupled with the ease of recovery and recycling of homogeneous acid catalysts. Although extensive efforts have been devoted to the fabrication of solid acid catalysts, they usually display inferior catalytic efficiencies in water-medium organic syntheses compared to their homogeneous compartments. The intrinsic problems in the heterogeneous catalytic systems are the decreased accessibility of actives sites and the enhanced diffusion limitation of reactants, leading to the declined catalytic reactivity and selectivity. Therefore, the fabrication of highly active, water-compatible and easily separable solid acid catalysts for chemical synthesis in water is highly urgent. In this dissertation, we synthesized a series of solid acids including graphene oxide and mesoporous phenol-formaldehyde resin based acid catalysts. We also explored their catalytic applications in the synthesis of 5-hydroxymethyl-furfural from fructose and cheap formaldehyde-participated Prins reactions. Detailed research summarizes are as follows.(1) Graphene oxide was synthesized by the previously reported Hummers method, which clearly showed the typical two-dimensional sheet-like structure. In the synthesis of 5-hydroxymethyl-furfural from fructose in water/sec-butyl phenol mixture, it gave the high yield of 5-hydroxymethyl-furfural(74%) after 2.0 h. The control experiments demonstrated that the high catalytic activity was attributed to its diminished diffusion limitation. Also, it could be also reused for several times, showing a good stability in biomass transformation.(2) Ordered mesoporous phenol-formaldehyde resin was synthesized by using evaporate induced self-assembly approach. After HSO3 Cl treatment, the direct transformation of phenyl groups in the framework to benzene sulfolic acid functional groups through generated Ph SO3-functionalized mesoporous phenol-formaldehyde resin. It still displayed high surface area, uniform pore size distribution and large volume. In the formaldehyde-participated Prins reaction, it exhibited excellent catalytic reactivity and high selectivity to 1,3-dioxane derivatives in pure water. The high catalytic performances could be due to that it could efficiently simultaneously adsorb hydropholic formaldehyde and hydrophobic olefin. Meanwhile, it could be reused for at least four times without the significant loss of catalytic activity, which was attributed to the existence of Ph SO3- groups in the framework.(3) Though ion-exchange treatment and Yb(OTf)3 coordination with Ph SO3-functionalized mesoporous phenol-formaldehyde resin, mesoporous Lewis acid resin was easily obtained. It still exhibited ordered porous structure and high surface area. It showed the different catalytic behavior with Ph SO3-functionalized mesoporous phenol-formaldehyde resin and gave the homoallyic alcohol product.