Vol.11 no.3 2019

Research paper : High-value materials from incineration residues of burnable garbage (N. FUKAYA et al.)−126−Synthesiology - English edition Vol.11 No.3 (2018) 2.3 For additional effective use of molten slagCurrently, there are high demands for civil engineering construction materials such as aforementioned road and concrete aggregates due to infrastructure construction for the 2020 Olympics and Paralympics as well as for recovery from earthquake disasters. However, there is concern that the amount of molten slag produced by garbage disposal plants may become excessive against the demand after the Olympics. Therefore, there is demand for technological development to create high added-value materials from molten slag and to enable effective use in wide-ranging elds. Mitsui E&S is an engineering company that conducts business with local governments to construct, operate, and maintain garbage disposal plants. The company has strong interest in developing methodology for effective use of molten slag, and was looking for technological potential at universities and public institutions to solve the problem.On the other hand, the Interdisciplinary Research Center for Catalytic Chemistry, AIST has been engaging in R&D for various organosilicon materials including silicone that was used in a wide-range of industrial fields in the NEDO Project “Development of the manufacturing process technology for organosilicon functional chemical products” (FY 2012–2021). The authors gave a poster presentation of the research results of the above NEDO Project at the AIST Techno Bridge held on October 22–23, 2015. R&D personnel of Mitsui E&S visited the exhibition and became interested in the content of “Direct synthesis of silicon key chemical products using silica as raw material.” They contacted the authors later, and the possibility for the effective use of molten slag and incineration ash that were produced from energy facilities was discussed, and joint research was started. In the following subchapter, we explain the outline of the technological potential created through the results of the NEDO Project that was the preliminary step to joint research.2.4 Outline of the NEDO Project “Development of the manufacturing process technology for organic silicon functional chemical products”Silicon is the second most abundant element after oxygen, among the components that comprise the earth surface. In nature, it exists in the form of silica that is the main component of rock and sand. There are many materials containing silicon around us, and it is used in various forms. The organic silicon chemicals represented by silicone and silane coupling agents have excellent physical properties from the viewpoints of heat resistance, weather resistance, chemical resistance, insulation property, and others. They are functional materials used widely in industrial elds such as of automobiles, aerospace, construction, electronics, medicine, cosmetics, and others. A compound called tetraalkoxysilane (e.g. tetraethoxysilane is known by the abbreviation TEOS) is widely used as raw material of inorganic silicon material and is a key substance essential for making protective lms for electronic devices, as well as optical materials such as functional ceramics, glass, and synthetic quartz.Chemical products containing silicon that are used in various materials must be reduced to metallic silicon by making the starting material, natural quartzite, react with carbon at high temperature. This process requires a large amount of electric energy, and at the same time, produces a large amount of carbon dioxide (CO2). This is the main factor that makes chemical materials containing silicon relatively expensive products, even though silicon is an element that exists abundantly on this planet. There is expectation for the development of technology to directly synthesize silicon-containing chemical products from silica that is reasonably priced and exists abundantly in Japan (Fig. 4).The authors aimed to develop a new manufacturing method for organic silicon chemical products that did not take the route of metal silicon, and worked on the development of technology to synthesize tetraalkoxysilane directly from silica, and succeeded in achieving a highly efcient reaction process. The characteristic of this technology is that a Fig. 3 Current situation of use of molten slag (from garbage and sewage sludge)[2]Fig. 2 Storage yard of molten slagRoad aggregate 33.7 %Concrete aggregate 16.9 %Soil stabilizer 7.5 %Cover soil for landll sites 4.9 % Foundation material for sewer pipes 5.5 %Backlling and banking 14.6 %Frost heave prevention material 0.2 %Others16.7 %

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