Catalytic Effect of Inherently-Water-Soluble Sodium on Zhundong Coal Gasification

Coal loaded with inherently-water-soluble sodium was prepared with dicyclohexyl-18-crown-6 to investigate the effects of inherently-water-soluble sodium on temperature-programmed isothermal gasification. The results were compared with Na 2 CO 3 -loaded coal using thermo-gravimetric analysis (TGA), and the results showed that sodium had a catalytic effect on gasification, and water-soluble sodium had a stronger catalytic ability than Na 2 CO 3 . The isothermal gasification reaction of inherently-water-soluble-sodium-loaded coal was complete in 4.68 min, whereas that of Na 2 CO 3 -loaded coal was complete in 5.39 min. Chemisorption of CO 2 to chars was investigated by TGA at 300 C, which showed that the order of CO 2 chemisorption capacity was similar to that of the catalytic abilities during gasification. Therefore, the CO 2 chemisorption capacity accurately reflects differences in the gasification reactivity. Moreover, the distribution of sodium in coal and char structures were investigated by multiple techniques, including scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD). EDS-mapping images of Na-loaded coal indicated that inherently-water-soluble sodium mainly adhered to coal particles. This finding shows that coal graphitization was strongly inhibited by inherently-water-soluble sodium, which further strengthened the chemisorption of CO 2 to char and the reactivity of char during gasification.