Na-Containing Mineral Transformation Behaviors during Na2CO3-Catalyzed CO2 Gasification of High-Alumina Coal

Interactions between alkali metals in catalysts and silicon or aluminum minerals in coal are closely related to gasification reactivity, deactivation, and recovery of alkali catalysts during coal catalytic gasification, and alkali-containing minerals and their transformation behaviors are key issues for understanding these interactions. In this paper, Na-containing mineral transformation behaviors and their influences on the catalytic performance during Na2CO3-catalyzed CO2 gasification of high alumina coal were comprehensively investigated by thermogtavimetry, inductively coupled plasma, X-ray diffraction, and Fourier transform infrared spectroscopy. Moreover, to have a better understanding of the mineral transformation during catalytic gasification, model,compounds, i.e., kaolinite (Al2O3 center dot 2SiO(2)center dot 2H(2)O) and boehmite (AlOOH), the main Al-containing minerals in high-alumina coal, were chosen as model compounds to investigate the mineral transformation behaviors. The results show that Na2CO3 first deactivates to generate inert sodium aluminum silicate (Na1.55Al1.55Si0.45O4) at 700 degrees C, which contributes to the deactivation of catalysts, and then various kinds of sodium aluminum silicates are formed with increasing temperature and Na2CO3 addition. Among them, sodium aluminum silicate [(Na2O)(0.33)NaAlSiO4] has been testified as the most stable mineral during gasification. In addition, Na-containing mineral transformation and its resulting products are helpful to the recovery of Al from the ash of catalytic gasification, and 94% recovery rate can be obtained, which is considered to be a method to extract Al from gasification ash. Model kaolinite and boehmite can well explain the mineral transformation during Na2CO3-catalyzed CO2 gasification of high-alumina coal.