Preparation, Characterization And Pilot-scale Application Of Porous Inorganic/polymer Composite In The Sugar Industry

With the development of the surface science and research of the composite materials, porous inorganic/polymer composite obtained more and more concerns of the academic because its unique properties. It has overcome some defects of the homogeneous materials and traditional composite materials. The composite not only has the advantages of inorganic material (such as stiffness and heat stability), but also has the advantages of polymer material (such as flexibility, dielectric properties, ductility and machinability). The inorganic porous particles in polymer matrix distributed uniformly, modified easily in the polymer matrix, controlled easily of the particle size, all these features give this kind of composite good performance in biology, environmental and chemical aspects.In this paper, aluminum sulfate, porous silica and water glass were used as the precursors of inorganic porous materials. In the preparation process of inorganic porous materials, organic materials, such as sodium alginate and chitosan, were added into inorganic porous materials with the in-situ generation method, and the porous inorganic/polymer composite was obtained at last. The composite was used to immobilize yeast cells as biocatalyst to produce fuel ethanol and to decolorize and purify sugarcane syrup in the process of high quality white sugar production. The research work mainly carried out in the following fields:1. Aluminum sulfate was used as the precursor of the pseudo-boehmite, and the pseudo-boehmite/alginate composite was prepared with the in-situ synthetic method. A detailed research of pore size, surface structure and mechanical properties of the pseudo-boehmite/alginate composite was studied. Then the composite was used to immobilize yeast cells with the coupling immobilization method of adsorption and embedment. The ethanol fermentation performance of the pseudo-boehmite/alginate immobilized yeast was studied using sugarcane molasses. With the research of proliferation mechanism, SEM, TEM characterization, pseudo-boehmite/alginate immobilized yeast showed yeast cell immobilized density at 4.1×10⁹ mL^-1, and good fermentation performance.2. Through the combining method of inorganic surface modification with a primary amino-reactive functional groups and organic embedding, a variety of modified zeolite/alginate composites were prepared by the coupling immobilization of physical adsorption and embedding. It was found that mesoporous molecular sieve MCM-41/alginate composite showed the highest fermentation activity of the yeast in the production of fuel ethanol with sugar cane molasses as raw stuff. The proliferation mechanism of the MCM-41/alginate immobilized yeast and the SEM of the carriers revealed the composite carrier is porous, which facilitates the transmission of substrates and products between carriers and medium. The experiments show that the composite carrier of MCM-41/alginate immobilized yeast has higher carrier ethanol productivity, lower residual sugar concentration than traditional technology, and can get higher conversion ratio of material and ethanol concentration.3. For the pseudo-boehmite/alginate immobilized yeast has the good immobilization and fermentation performance, pseudo-boehmite/alginate immobilized yeast was used in pilot-scale continuous fermentation experiments of 30 L×2 and 10 m³Ã—2. The experiments showed that the immobilized yeast of pseudo-boehmite/alginate has higher ethanol fermentation rate, lower residual sugar concentration than traditional technology, and can get higher conversion ratio of material and ethanol concentration. The new kind of fermentation process can reduce the production costs of raw materials. It is suitable for the sugar industry to produce the fuel ethanol in the large-scale.4. In the current sugar production, the residual sulfur dioxide concentration remains high, and the characteristics of the white sugar product is unsteady. All of these defeats are harmful to human health. In this article, porous silica and water glass was used as the precursor of silica source, with the methods of surface modification of inorganic particles and in-situ synthetic, several types of silica/chitosan composites was prepared and used in the decolorization and purification process of sugarcane juice and syrup. The in-situ synthetic silica/chitosan composites has the best performance in the detreated purification. Through SEM, TEM characterization, the interface of inorganic-organic of the composites was compact, and the in-situ synthetic silica/chitosan composite has excellent performance in the absorption of non-ferrous elements and sugarcane juice and syrup.5. In-situ synthetic silica/chitosan composites was studied with detail, such as effect of temperature, LHSV, and duplicate renewable abilities in the red sugar remelting juice. With the help of Yunnan sugar factory, 12 L pilot-scale experiments of in-situ synthetic silica/chitosan composites were carried out, the decolorization ratio of syrup was higher than 80% with easy operation method and low cost, which played an important role in upgrading sugar products and environmental protection.