Research On Silicon Dioxide Surface Chemically Modified And It's Application In Environment

With the development of science and technology, the demand on materials is becoming higher and higher. Research on new materials, which have better properties including lower cost and stronger rivalrousness, is of great importance. In which, inorganic supports surface chemically modified is the most important field, such as silica gel, alumina, zirconia and carbon and so on. Study on their application in solid-phase extraction and catalytic esterification has great significance.Solid-phase extraction is a new technology that is used in pre-treatment of environmental samples recently, some stationary phase based on silica gel and diatomite are widely utilized in enriching, separating and purifying over 80% organic compounds.The applied research on the utilization of solid acid in organic synthesis has become an important field in the latest decades. Solid acid has overcome the disadvantages of liquid acid and have its own characteristics including easily separated from liquid phase, no erode equipments, simple post-treatment, fewer pollutants discharged into the environment and high selectivity and so on. It can be used in wide temperature range and make acid catalytic reaction possible in thermodynamics. Esterification is a reversible reaction, and it must be happen in the presence of catalyst if we want to obtain high production and shorten reaction time. Solid acid that can be used in esterification include SO₄^2-/ZrO₂, zeolite and strongly acidic cation exchange resin.This paper mainly introduced the research on stationary phase, the definition and applied status of solid-phase extraction, the definition and classification of solid acid, and the properties of solid acid catalytic esterification. We synthesized a series of new packing materials and solid acid catalyst using silica gel surface chemically modified with silylated reagents that contain phenyl or long-straight alkyl and sulfonation. Various physicochemical techniques were applied for the characterization of the surface of obtained packings. The progress of the modification reactions wasconfirmed by thermal analysis, elemental analysis, which allowed calculation of the surface coverage density with bonded ligands. Created undersurface structure was examined by means of FT-IR spectroscopy and BET. Through the experiments of enriching the paraquat and PCP-Na in water and solid acid catalytic synthesis of butyl acetate, the effect of the quantity of added catalyst, reaction time, lifetime of the catalyst, stir and different catalyst on production and selectivity are discussed in the paper.The SPE experiments' results indicated that the enriched efficiency on paraquat and PCP-Na varied distinctly with the packing materials: The packings that contain Ci8 have the highest efficiency, while the large silica gel samples are higher than the small ones and the packings bonded phenyl trichlorosilane are higher than those bonded diphenyl dichlorosilane, in terms of the same stationary phase, the efficiency on paraquat is higher than PCP-Na. So the efficiency is determined by not only the extractible mechanism but also the solubility of paraquat and PCP-Na.As far as the experiment of catalytic synthesis of butyl acetate using solid acid, the production of large silica gel sample is higher than the smaller one and diatomite support, the needed quantity of added catalyst is also different when reaching the highest production. It is because the aperture of large silica gel is big enough that the acetic acid and butyl alcohol could pass through smoothly, which enhance the chance of reaction. So the esterification can be happened inside. While the small silica gel and diatomite are not as splendid as the former. And in this paper, the production of solid acid is not only related with the quantity of-SO3H but also the aperture and BET area. Research on the production of H2SO4 and strongly acid macro porous adsorptive resin indicated that their productions are all lower than the solid acids that were synthesized in our experiment.