Studies of Adsorption Characteristics in Supercritical Fluids by FTIR and Spectroscopic Measurements

通过 FTIR 和光谱测量研究超临界流体的吸附特性

基本信息

批准号：
07650896
负责人：
NITTA Tomoshige
金额：
$ 1.34万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

The present work has been intended to investigate the adsorption characteristics in supercritical fluids by using two different methods, Infrared spectroscopy and Chromatography. In spectroscopic measurements, IR spectra were obtained for adsorption systems composed of an organic solvent diluted in supercritical CO_2 on a large-pore Silica Gel (SG800) from atmospheric pressure to 15 MPa at 313.2 K.The organic solvents we measured are methanol, acetone, triethylamine, acetonitrile, tetrahydrofuran, and diethyl ether. A most important result to be noted is that all the intensities of hydrogen-bonded OH bands of sylanol, except for a system of triethylamine, showed a maximum at about 20-50 MPa and then they dcreased with increasing pressure. The characteristic curves of the IR observations are almost the same as the adsorption isotherms calculated by Monte Carlo simulations for a system of benzene diluted in supercritical CO_2 in slitpores of graphitic walls. The molecular simulations hav … More e already suggested two factors for adsorption characteristics in supercritical fluids : that is, an increase in solubility into a supercritical fluid and an increase in competitive adsorption of the solvent (CO_2) molecules with increasing pressure.A supercritical fluid chromatograph, newly constructed in the present work by use of commercial pumps, has been used for measuring the adsorption isotherms of acetone and benzene on SG800 in supercritical CO_2. The elution curves obtained showed a large tailing forming a common envelope for different amount of injections, which indicated that (a) the ECP (Elution by Characteristic Point) method was applicable for obtaining the adsorption isotherms of solutes and (b) the SG800 has energetically heterogeneous surfaces that should be taken into consideration for a theoretical analysis.The results obtained in the present work may be summarized as follows. (1) The isotherm curves of acetone obtained from the chromatographic measurements qualitatively coincide with the isotherms obtained from the IR spectroscopy. (2) The adsorption isotherms of the chromatographic measurements decrease more in the high-pressure region, which may be attributable to the less contribution of the van der Waals force on adsorption in the region of high competitive-adsorption. (3) The adsorption isotherms of benzene in CO_2 resemble those of acetone though benzene molecules do not show hydrogen-bonding with OH groups on silica gel while acetone molecules show an IR spectroscopic evidence of hydrogen-bonding. Less

目前的工作旨在通过使用两种不同的红外光谱和色谱法研究超临界烟的吸附特性。在光谱测量中，获得了IR光谱的吸附系统，该系统由在超临界co_2中稀释的有机溶液组成的大孔硅胶（SG800），从大气压到313.2 K的15 MPa。要注意的最重要的结果是，除三乙胺系统外，氢键键入OH带的所有强度在约20-50 mPa下显示出最大值，然后随着压力增加而干燥。 IR观测值的特征曲线几乎与由Monte Carlo模拟计算出的吸附等温线相同，用于在图形壁的Slitpores中稀释在超临界CO_2中的苯系统。分子模拟已经……已经提出了超临界液中添加吸附特征的两个因素：也就是说，溶解度增加到超临界液体中的溶解度以及溶液的竞争添加吸收（CO_2）分子的增加而增加了压力的增加。超临界CO_2中的SG800苯。所获得的洗脱曲线显示出大型尾部，形成了不同量的注射量的常见包络，这表明（a）ECP（按特征点进行洗脱）适用于获得太阳能的吸附等温线，并且（b）SG800本质上应考虑到众所周知的分析。（1）从色谱测量获得的丙酮等温线与从IR光谱法获得的等温线一致。（2）在高压区域中，色谱测量值的添加等温线减少，这可能归因于范德华力对高竞争性吸附区域的吸附的贡献较小。（3）尽管苯分子在硅凝胶上没有与OH基团显示氢键，而丙酮分子在丙酮分子上显示出IR光谱证据，但CO_2中苯的添加等温线类似于丙酮的等温线。较少的