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Isotopic homogenization and scrambling associated with oxygen isotopic exchange on hot platinum: studies on gas pairs (O-2, CO2) and (CO, CO2)

机译：与热铂的氧同位素交换相关的同位素均质化和争吵：气体对研究（O-2，CO2）和（CO，CO2）

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摘要

The catalytic exchange between O-2 and CO2 on hot platinum leads to isotope scrambling in CO2 and homogenization of the oxygen isotopes in the two phases (O2 and CO2) even though the two gases could be widely different in isotope ratios from each other (e.g., about 45 parts per thousand in delta O-18) before the exchange. After the exchange, the d(18)O values of the gases become close to each other (within 2 parts per thousand) depending on the time and temperature. The clumped-isotope analysis of the post-exchange CO2 samples shows that the Delta(47) values (relative to the pre-exchange values) decrease with increase in temperature from near zero (at similar to 25 degrees C) to about similar to 0.8 +/- 0.1 parts per thousand (at similar to 700 degrees C). The low value of -0.8 parts per thousand equals the values typically obtained for pure CO2 heated to 1000 degrees C inside quartz tubes suggesting a scrambled state. If the catalytic exchange between CO2 and O-2 is associated with isotopic scrambling (or random mixing) a microscopic mechanism of isotopic mixing can be inferred. It seems that CO2 and O-2 dissociate in the adsorbed state on platinum (or quartz surfaces) and the product CO molecules and O atoms mix uniformly while doing a random walk on the hot surface and produce two reservoirs (CO and O) where the three oxygen isotopes are randomly distributed. This can produce the observed internal isotopic scrambling in CO2 when CO and O recombine to form CO2 molecules on the platinum surface and desorb. Experiments using CO-CO2 gas pairs over hot platinum also show homogenization showing exchange of CO as a molecular entity and supporting the suggested mechanism.
机译：在炎热的铂引线O2和CO2之间的催化交换的同位素中的CO 2和在两个相中的氧同位素的均质化（O2和CO2）的加扰，即使这两种气体可以在彼此同位素比率差异很大（例如，每千约45份在交换之前增量-O-18）。在交换之后，气体的d（18）O值变得彼此靠近（内每千2份）取决于时间和温度。的交换后CO2样品显示结块的同位素分析认为，德尔塔（47）的值（相对于预交换值）与从接近零的温度升高（以类似于25℃）至约类似0.8下降+/-每千0.1份（以类似于700摄氏度）。 -0.8千分之低值等于通常对于加热到1000摄氏度表明加扰状态的石英管内纯的CO 2获得的值。如果CO 2和O-2之间的催化交换用同位素加扰（或随机的混合）同位素混合的显微机构相关联可以推断。这似乎在吸附状态的CO2和O-2解离上的铂（或石英表面）和产物CO分子和O原子均匀混合，而这样做的热表面上的随机游动，并产生两个储存器（CO和O），其中三个氧的同位素是随机分布的。这可能会产生所观察到的内部同位素在CO2加扰时，铂表面和解吸上CO和O重新结合形成CO 2分子。使用CO-CO 2气体对在热铂实验还表明均一化表示CO的交换作为分子实体和支撑所建议的机制。

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  • 来源
    《RSC Advances》 |2016年第56期|共8页
  • 作者

    Prasanna K.; Bhattacharya S. K.; Ghosh Prosenjit; Mahata Sasadhar; Liang Mao-Chang;

  • 作者单位

    Indian Inst Sci Ctr Earth Sci Bangalore 560012 Karnataka India;

    Indian Inst Sci Ctr Earth Sci Bangalore 560012 Karnataka India;

    Indian Inst Sci Ctr Earth Sci Bangalore 560012 Karnataka India;

    Acad Sinica Res Ctr Environm Changes Taipei 115 Taiwan;

    Acad Sinica Res Ctr Environm Changes Taipei 115 Taiwan;

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