![]() But the absence of recyclability and difficult separation from the reaction mixture has led scientists to use heterogeneous catalysts. It should be noted that the efficiency of homogeneous catalysts is higher than that of heterogeneous catalysts due to the proper treatment of reactants. There are several reasons for this, including high stability, reusability, and ease of separation from the reaction media. Recently, the use of magnetic heterogeneous metal catalysts in organic reactions has been developed. development of new methods for producing Cu(I) catalyst in situ by the reduction of Cu(II) or oxidation of Cu(0) to Cu(I) was expanded 17. ![]() disproportionation reactions, need to the inert atmosphere, formation of undesired by-products, etc. The germania and niobium precursor is highly active, the water amount in the solvents used as received without drying process can meet the surface sol-gel coating without precipitates and gelation formed before finishing coat.įor germania -PDMDPS column, thermal stability is very important because of the temperature for remaining the low residual OH- group in silica and germania film at 350 ☌.Due to the complexity of using Cu(I), e.g. Basic parameters for dynamic coating and static coating with conventional coating and surface sol-gel were acquired for further development. The coating results proved the sol-gel stationary phase could be fulfilled with diluted sol solution by static coating. Without the TFA as the catalyst, the sol-gel matrix may not form effective surface area and porosity to support the functional polymer for separation, the column performances were two third of the protocol column, at 1500-2500 plate number per meter. From the retention time of the grob mixture, the surface sol-gel coated 2 meters of column acquired the half retention time, grob mixture analytes were eluted within 7 minutes, compared with conventional sol-gel coated column eluted within 14 minutes. Without the catalyst, the sol solution has constant viscosity and gelation time is much longer, the sol-gel reaction was taking on the silica surface only, to accomplish the thinner coating for sol-gel stationary phase. The backpressure of the short steel column and capillary both were beyond the pressure limit of conventional HPLC pump.Ĭhapter three demonstrates the new ideal of the surface sol-gel process for GC stationary phase. The preliminary HPLC testing showed the core-shell particles had more retention ability compare with 4 um commercial core particles. The function of the core-shell particles was slurry packed with 5cm regular steel column and the capillary column with sol-gel frit. 2 um core-shell particles were successfully prepared from the external composition (1.7 um core, 0.3 um shell). Then the carbon loading with C 18 for surface derivatization were also confirmed with EDS testing. EDS characterize the extended layers of germanium oxide has been coated at ratio 12/1(Ge/Si). The extended layer of germanium oxide coating was made with acid and alkaline as a catalyst. Conventional silica core particles were prepared with stÖbe methods. The basic recipe and preparation of sol-gel process were verified by tungsten alkoxide incorporated with poly(dimethyldiphenylsilanoxan) as the stationary phase which arrived the same plate number level at 3800 per meter.Ĭhapter three demonstrated the preparation of core-shell particle for HPLC. ![]() The theoretical plate number reached the 3200 plates per meter, and the optimized plate number arrived at the top level at 3800 plates per meter. The chapter two reported the non-silica-based metal alkoxide oxide as the new building block, cooperated with known polymer poly(dimethyldiphenylsilanoxan), developed the original nonpolar feature of the stationary phase to broad the polarity from the nonpolar to extreme polar, overcome the thermal stability for other types of polar column. The sol-gel chemistry with essential structure rebuilding will make sol-gel stationary phase to a new level. Partial derivatizations of known polymers have not increased the column performance but remained at the same level of 3200 plates per meter. Chemical bound stationary phase significantly improve GC column with better thermal stability and solvent stability. Inorganic sol-gel precursor creates the substrate support for stationary phase bind to silica surface through the condensation of silanol groups, the rough surface with enhanced surface area enlarger the capacity of the sol-gel stationary phase, the porosity of sol-gel structure decreases the mass transferring coefficient, the term C in Van Deemter equation, which makes sol-gel stationary phase thicker coating up to 1 um but keeps the high resolution for gas chromatography. Chapter one reviewed the development of sol-gel stationary phase for gas chromatograph (GC). ![]()
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