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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Kinetic and equilibrium study on formic acid decomposition in relation to the water-gas-shift reaction
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Kinetic and equilibrium study on formic acid decomposition in relation to the water-gas-shift reaction

机译：甲酸分解与水煤气变换反应的动力学和平衡研究

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摘要

Kinetics and equilibrium are studied on the hydrothermal decarbonylation and decarboxylation of formic acid, the intermediate of the water-gas-shift (WGS) reaction, in hot water at temperatures of 170-330 degrees C, to understand and control the hydrothermal WGS reaction. H-1 and C-13 NMR spectroscopy is applied to analyze as a function of time the quenched reaction mixtures in both the liquid and gas phases. Only the decarbonylation is catalyzed by HCl, and the reaction is first-order with respect to both [H+] and [HCOOH]. Consequently, the reaction without HCl is first and a half (1.5) order due to the unsuppressed ionization of formic acid. The HCl-accelerated decarbonylation path can thus be separated in time from the decarboxylation. The rate and equilibrium constants for the decarbonylation are determined separately by using the Henry constant (gas solubility data) for carbon monoxide in hot water. The rate constant for the decarbonylation is 1.5 x 10(-5), 2.0 x 10(-4), 3.7 x 10(-3), and 6.3 x 10(-2) mol(-1) kg s(-1), respectively, at 170, 200, 240, and 280 degrees C on the liquid branch of the saturation curve. The Arrhenius plot of the decarbonylation is linear and gives the activation energy as 146 +/- 3 kJ mol(-1). The equilibrium constant K-CO = [CO]/[HCOOH] is 0.15, 0.33, 0.80, and 4.2, respectively, at 170, 200, 240, and 280 degrees C. The van't Hoff plot results in the enthalpy change of Delta H = 58 +/- 6 kJ mol(-1). The decarboxylation rate is also measured at 240-330 degrees C in both acidic and basic conditions. The rate is weakly dependent on the solution pH and is of the order of 10(-4) mol kg(-1) s(-1) at 330 degrees C. Furthermore, the equilibrium constant K-CO2 = [CO2][H-2]/[HCOOH] is estimated to be 1.0 x 10(2) mol kg(-1) at 330 degrees C.
机译：在170-330摄氏度的热水中，研究了甲酸的水热脱羰和甲酸的水热脱羰和脱羧的动力学和平衡，以了解和控制水热WGS反应。 H-1和C-13 NMR光谱用于分析液相和气相中淬灭的反应混合物随时间的变化。 HCl仅催化脱羰作用，相对于[H +]和[HCOOH]，反应都是一级反应。因此，由于未抑制的甲酸电离，不含HCl的反应处于第一个（1.5）级。因此，可以在时间上将HCl加速的脱羰路径与脱羧分离。通过使用热水中一氧化碳的亨利常数（气体溶解度数据）分别确定脱羰基反应的速率常数和平衡常数。脱羰反应的速率常数为1.5 x 10（-5），2.0 x 10（-4），3.7 x 10（-3）和6.3 x 10（-2）mol（-1）kg s（-1）分别在饱和曲线的液体分支上的170、200、240和280摄氏度下进行。脱羰基的Arrhenius图是线性的，给出的活化能为146 +/- 3 kJ mol（-1）。在170、200、240和280摄氏度时，平衡常数K-CO = [CO] / [HCOOH]分别为0.15、0.33、0.80和4.2。范霍夫图导致的焓变为δH = 58 +/- 6 kJ mol（-1）。还在酸性和碱性条件下在240-330摄氏度下测量脱羧速率。该速率在弱弱程度上取决于溶液的pH值，在330摄氏度时约为10（-4）mol kg（-1）s（-1）。此外，平衡常数K-CO2 = [CO2] [H -2] / [HCOOH]在330摄氏度下估计为1.0 x 10（2）mol kg（-1）。

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