Stolte Nore, Yu Junting, Chen Zixin, Sverjensky Dimitri A, Pan Ding
Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
J Phys Chem Lett. 2021 May 6;12(17):4292-4298. doi: 10.1021/acs.jpclett.1c00563. Epub 2021 Apr 30.
The water-gas shift reaction is one of the most important reactions in industrial hydrogen production and plays a key role in Fischer-Tropsch-type synthesis, which is widely believed to generate hydrocarbons in the deep carbon cycle but is little known at extreme pressure-temperature conditions found in the Earth's upper mantle. Here, we performed extensive ab initio molecular dynamics simulations and free energy calculations to study the water-gas shift reaction. We found the direct formation of formic acid from CO and supercritical water at 10-13 GPa and 1400 K without any catalyst. Contrary to the common assumption that formic acid or formate is an intermediate product, we found that HCOOH is thermodynamically more stable than the products of the water-gas shift reaction above 3 GPa and at 1000-1400 K. Our study suggests that the water-gas shift reaction may not happen in the Earth's upper mantle, and formic acid or formate may be an important carbon carrier in reducing environments, participating in many geochemical processes in deep Earth.
水煤气变换反应是工业制氢中最重要的反应之一，在费托合成中起着关键作用。人们普遍认为费托合成在深部碳循环中生成碳氢化合物，但在地球上地幔发现的极端压力 - 温度条件下却鲜为人知。在此，我们进行了广泛的从头算分子动力学模拟和自由能计算来研究水煤气变换反应。我们发现，在10 - 13吉帕和1400 K的条件下，一氧化碳和超临界水在无任何催化剂的情况下直接生成甲酸。与甲酸或甲酸盐是中间产物这一常见假设相反，我们发现，在3吉帕以上和1000 - 1400 K时，甲酸在热力学上比水煤气变换反应的产物更稳定。我们的研究表明，水煤气变换反应可能不会发生在地球上地幔中，并且甲酸或甲酸盐可能是还原环境中一种重要的碳载体，参与地球深部的许多地球化学过程。
