【正文】 Supercritical fluid chromatography (SFC) a. mobile phase is a supercritical fluid. b. first proposed in 1958 by J. Lovelock. first report use was in 1962 by Klesper et al, who used it to separate thermallylabile porphyrins(卟啉 ). c. permits the separation and determination of a group of pounds that are not conveniently handled by either GC or LC. nonvolatile or thermally labile so that the GC are inapplicable, contain no functional groups for detection by spectroscopic or electrochemical techniques employed in LC. Theory of SFC a. One of advantages is that supercritical fluid have lower densities and viscosities than liquids. This results in larger diffusion coefficients for solutes in SFC than LC. This results in Better efficiencies and higher optimum linear Velocities in SFC than LC. b. SFC have higher densities than gas, so that mobile phase has a greater chance of interacting with the solute than that in GC (., carrier gas). This makes the mobile phase important in determining the retention of solutes on the system and give more flexibility in optimizing the separation. For example, retention of solutes in SFC can be changed by using a different column (. different stationary phases) as in GC, or by changing the mobile phase strength as in LC. c. One major advantage of SFC is its ability to use detector available for either GC or LC, such as FID, UVVis, and Fluorescence detectors. This gives it a wide range of both universal and selective detections for use in either analytical or preparativescale work. d. Depending on which supercritical fluid is used, it is also possible to use SFC at lower T than GC. This makes it more useful in the separation of thermally unstable pounds. e. The stationary phases used in SFC can be similar to those in LC as well as GC. Either packed or opentubular columns may be used. Because of these advantages, SFC is monly viewed as a technique which is plementary to both LC and GC. Instrumentation a. Instrumentation for SFC can be obtained mercially or adapting system used for either LC and GC. b. The main difference of a SFC than a LC or GC system is the need to control both temperature and pressure of mobile phase. This must be done to keep the mobile phase as a supercritical fluid. Control of the pressure (density) of the supercritical fluid can also used to vary strength of mobile phase during the gradient elution in SFC . isobaric Pressure programming Flowrate programming Supercritical fluid chromatography Applications By now, SFC has been applied to a wide variety of materials, including natural products, drug, foods, pesticides and herbicides, surfactants polymers, and polymer additives, fossil fuels, and explosives and Propellants. 超臨界流體技術展望 雖然超臨界流體技術在許多方面已得到應用 ,但還遠沒有發(fā)揮其應有的作用 .這主要是因為目前對超臨界流體性質的認識還遠遠不夠。 M. Ali, . Oakes, . Clifford and Rayner, unpublished results. Stereochemistry confirmed by Xray Crystallography N H C b zM e OOS +M eO Other substrates ? Replacing the Cbz group with Boc has a significant effect on selectivty ?No diastereoselectivity observed in conventional solvent ?Major isomer is now syn! . Oakes, . Clifford, . Bartle, M. Thornton Pett, and . Rayner, Chem. Commun., 1999, 247。O O1 0 % V O ( a c a c ) 2T B H P ( 4 . 3 5 M )s c C O 2 , 4 0 o C , 2 0 0 b a r2 0 h o u r so r C H 2 C l 2 , r . t .R S R 39。 R S R 39。 超臨界流體在催化反應中的優(yōu)勢 超臨界流體 延長催化劑壽命及再生催化劑 控制選擇性 加強傳質和傳熱 方便分離 強化反應過程 催化劑制備 提高反應速率 超臨界流體在催化反應中的應用展望 超臨界流體在催化反應中的應用還剛剛開始 ,但其獨特的性 能和已有成功應用都證明了其在催化反應中運用的巨大潛力。但在 超臨界相中 由于空間位阻和中間產物易從催化劑表面脫附 ,順式成為主要產物 ,并且順反比隨壓力的增加而增加。 Complete. Catalyst activity histories during hexene isomerization on a shelltype Al2O3 catalyst Angew. Chem. Int. Ed. Engl. 1981, by H. Tiltscher Enhancing the stability of porous catalysts with supercritical reaction media 超臨界流體在催化反應中的應用 反應速率、產率、選擇性等可用壓力調節(jié)，可將非均相反應變成均相反應，改善非均相反應的傳質速度，用環(huán)境友好溶劑取代有害溶劑，可將化學反應與分離過程結合起來等。 超臨界流體催化反應 超臨界流體 催化加氫 超臨界水氧化反應 scCO2氫甲?；磻? HeckStille反應 催化加氫 不對稱加氫 % 81%ee % 不飽和烯烴在 scCO2進行不對稱加氫 , 具有很高的立體選擇性 ,同時反應沒有任何堿參與 ,而無副產物生成 . Science 1995 Jessop CO2加氫 CO2 + H2 HCOOH Ru cat SC CO2 323K scCO2 可以溶解三甲基膦配體的 Ru催化劑 ,使其成為高分散均相體系 , 而且還可溶解大量 H2, 使體系達到高的 H2/CO2混合比