Process characteristics and mechanism of Na2CO3-catalyzed water-gas shift reaction in a benzene-containing hydrothermal system

Abstract

Water-gas shift reaction (WGSR) is one of the most crucial reactions in the lignite-liquefaction system containing syngas (CO + H2) and H2O. In this study, the characteristics of WGSR were investigated in similar liquefaction systems, such as a benzene-containing hydrothermal system employing Na2CO3 as a catalyst. The CO conversion and productions of CO2 and H2 during WGSR in these systems of 20–60% water content were investigated at 350–450 °C. The results demonstrated that as the reaction temperature and water content increased, CO conversion increased, thereby resulting in enhanced WGSR. When benzene was added to the hydrothermal system, the activity of WGSR reduced evidently because of the inhibition effect of benzene. Moreover, when Na2CO3 was added to the benzene-containing hydrothermal system, the activity of WGSR was enhanced, indicating that Na2CO3 exerted a strong promoting effect on WGSR. Noticeably, in this benzene-containing hydrothermal system with Na2CO3 as the catalyst, the productions of H2 and CO2 were not equal to the consumption of CO during WGSR. This was due to the formation of intermediate products, such as NaHCO3, NaOH, HCOONa, and Na2C2O4. Based on the foregoing, the Na2CO3-catalyzed WGSR was accelerated via the ionic reactions of these intermediate products. Therefore, the mechanism of Na2CO3-catalyzed WGSR in a hydrothermal system with an organic solvent was developed, thereby affording an insight into the lignite-liquefaction technology in syngas and H2O systems.