Department of Chemical Engineering, University College London, London, WC1E 6BT, United Kingdom.
Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, AL, 35487, United States.
Sci Rep. 2017 Aug 21;7(1):9021. doi: 10.1038/s41598-017-09445-1.
An important scientific debate focuses on the possibility of abiotic synthesis of hydrocarbons during oceanic crust-seawater interactions. While on-site measurements near hydrothermal vents support this possibility, laboratory studies have provided data that are in some cases contradictory. At conditions relevant for sub-surface environments it has been shown that classic thermodynamics favour the production of CO from CH, while abiotic methane synthesis would require the opposite. However, confinement effects are known to alter reaction equilibria. This report shows that indeed thermodynamic equilibrium can be shifted towards methane production, suggesting that thermal hydrocarbon synthesis near hydrothermal vents and deeper in the magma-hydrothermal system is possible. We report reactive ensemble Monte Carlo simulations for the CO methanation reaction. We compare the predicted equilibrium composition in the bulk gaseous phase to that expected in the presence of confinement. In the bulk phase we obtain excellent agreement with classic thermodynamic expectations. When the reactants can exchange between bulk and a confined phase our results show strong dependency of the reaction equilibrium conversions, [Formula: see text], on nanopore size, nanopore chemistry, and nanopore morphology. Some physical conditions that could shift significantly the equilibrium composition of the reactive system with respect to bulk observations are discussed.
一个重要的科学争论集中在海洋地壳-海水相互作用过程中烃类的非生物合成的可能性上。虽然热液喷口附近的现场测量支持这种可能性，但实验室研究提供的数据在某些情况下是相互矛盾的。在与地下环境相关的条件下已经表明，经典热力学有利于从 CH 生产 CO，而非生物甲烷合成则需要相反的条件。然而，封闭效应已知会改变反应平衡。本报告表明，热力学平衡确实可以向甲烷生成方向转移，这表明热烃合成在热液喷口附近和更深的岩浆-热液系统中是可能的。我们报告了 CO 甲烷化反应的反应系综蒙特卡罗模拟。我们将预测的平衡组成与存在封闭时的预期进行了比较。在本体相中，我们得到了与经典热力学预期的极好一致性。当反应物可以在本体相与封闭相之间交换时，我们的结果表明反应平衡转化率 [Formula: see text] 对纳米孔尺寸、纳米孔化学和纳米孔形态具有很强的依赖性。讨论了一些可能会使反应体系的平衡组成相对于本体观察发生显著变化的物理条件。
