Ethanol Decomposition in Supercritical Water: An Operating Parametric Experimental and Kinetic Study

Liang Zhao, Yuhang Yang, Hongfang Zhou, Zhengle Que, Yadi Pan

Abstract


Ethanol is an intermediate of the supercritical water decomposition of lignocellulosic biomass or biomass-derived compounds. In this study, experiments on ethanol decomposition in supercritical water were performed at different reaction temperatures (500 °C to 600 °C), residence times (6 s to 12 s), and initial ethanol concentrations (0.05 mol·L-1 to 0.20 mol·L-1). Temperature had larger impacts on the ethanol conversion than the other factors. Higher temperatures and feedstock concentrations facilitated gas production. In addition, the higher temperature promoted the scissions of C-C and C-O bonds of ethanol. However, longer residence times did not improve the yields of H2, CO, and C2. Because the H2-to-CO2 ratio was much greater than 1, the water-gas shift reaction was not the dominant route during the ethanol conversion process. Further, the mechanism and kinetic model of ethanol supercritical water decomposition were proposed. The kinetics revealed that ethanol gasification in supercritical water was mainly dominated by ethanol dehydrogenation, the hydrogenation of intermediates, and the coke formations of CO and CH4. In addition, H2 was mainly formed via ethanol dehydrogenation and consumed via the hydrogenation of intermediates. The rate of coke formation was relatively low during ethanol decomposition.

Keywords


Ethanol; Supercritical water; Decomposition; Kinetics

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