supercriticalextract超臨界(已修改)
2025-05-19 18:13 本頁面
【正文】 Supercritical Fluid Extraction Historical ? The first reported observation of the occurrence of a supercritical phase was made by Baron Cagniard de la Tour in 1822. ? He noted visually that the gasliquid boundary disappeared when the temperature of certain materials was increased by heating each of them in a closed glass container. ? From these early experiments, the critical point of a substance was first discovered. Historical ? The first workers have been done to demonstrate the solvating power of supercritical fluids for solids in 1879. ? In 1970 a significant development in supercritical fluid extraction(SFE), provided incentive for extensive future work, which involved decaffeination of green coffee with CO2. Historical coffee Historical ? Since 1980, there has been rapid development of SFE for the extraction of ? (1) hops。 ? (2) cholesterol from butter。 ? (3) perfumes and flavors from natural products。 ? (4) residual solvents and monomers from polymers。 ? (5) unsaturated fatty acids from fish oils. Hops(啤酒花 ) unsaturated fatty acids Properties of supercritical fluids ? A supercritical fluid is any substance above its critical temperature and critical pressure. In the supercritical area there is only one stateofthefluid and it possesses both gas and liquidlike properties. Phase diagram（ PT） Properties of supercritical fluids Properties gas SCF liquid 1bar， 15～ 30℃ Tc， Pc Tc， 4Pc 15～ 30℃ density/(g/mL) (~2) 103 ~ ~ ~ viscocity/ [g/(cm﹒s)] (1~3) 104 (1~3) 104 (3~9) 104 (~3) 102 diffusion coefficient /(cm2/s) ~ 103 103 (~3) 105 Properties of supercritical fluids ? A supercritical fluid exhibits physicochemical properties intermediate between those of liquids and gases. Characterisitics of a supercritical fluid are : ? Dense gas ? Solubilities approaching liquid phase ? Diffusivities approaching gas phase. 1 密度 類似液體，因而溶劑化能力很強，壓力和溫度微小變化可導(dǎo)致其密度顯著變化 2 粘度 接近于氣體 ,具有很強傳遞性能和運動速度 3 擴散系數(shù) 比氣體小，但比液體高一到兩個數(shù)量級；
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