Correlation between Microscopic Structure and Chemical Reaction in Low-density Supercritical Water

(1)构建了用于XAFS、小角x射线和中子散射的高温高压溶液样品池。电池使用的最大压力和温度分别为50mpa和400cc。(2)在0.1 M Co(N03)2水溶液中，分别在25、250、400三种温度下进行了XAFS测量。结果表明，Co^<2+>的水化数由25℃时的6个降至400℃时的4个，Co- h_2距离为2.06 ~ 2.08 A。(3)采用羟基H/D取代的中子衍射和经验参数结构精化方法研究了常温（25 C）、亚临界（202 C）和超临界（253 C）下甲醇的结构。研究发现，甲醇分子通过氢键呈链状排列，在超临界温度下形成5-6个甲醇分子的团簇，并随着密度的减小而分解。(4)对甲醇-水二元溶液（甲醇摩尔分数为0.3）在25-200偶联温度范围内进行了x射线衍射测量。发现2.9 A的氢键大部分被破坏，3.5 A的非氢键增加。(5)采用^<35>C/^<37>C取代、EPSR和球谐展开等方法，用中子衍射法推导了超临界水中Cl水化的取向相关函数。在Cl周围的所有水分子都保持在第一配位壳层，但随机朝向Cl。

(1)High-temperature and high-pressure solution sample cells for XAFS, small-angle X-ray and neutron scattering have been constructed. Maximum pressure and temperature used for the cells are 50 MPa and 400 ﾟC.(2)XAFS measurements on 0.1 M aqueous Co(N03)2 solution were made at 25ﾟC(0.1 MPa), 250ﾟC(30 MPa), and 400ﾟC(35 MPa). It has been found that the hydration number of Co^<2+> decreases from 6 at 25ﾟC to 4 at 400ﾟC, the Co-H_2 distance being 2.06-2.08 A.(3)The structure of methanol at ambient (25ﾟC), subcritical (202ﾟC), and supercritical(253ﾟC)temperatures has been investIgated by neutron diffraction with hydroxyl H/D) substitution and Empiricat Parameter Structure Refinement methods. It has been found that methanol molecules are arranged as chain-like by hydrogen bonding and that clusters of 5-6 methanol molecules are formed at the supercritical temperature and are broken down with decreasing density.(4)X-ray diffraction measurements on a methanol-water binary solution (methanol mole fraction is 0.3) were made over a temperature range 25-200ﾟC.It has been found that hydrogen bonds at 2.9 A are largely broken down with increasing non-hydrogen bonds at 3.5 A.(5)The orientational correlation function on Cl hydration in supercritical water has been derived by neutron diffraction on a 3 m LiCl solution in D_2 with ^<35>C/^<37>C substitution, EPSR, and spherical harmonic expansion methods. It has been found that all water molecules around Cl remain in the first coordination shell, but are randomly oriented toward Cl.