Green synthesis of mesoporous γ-Al2O3 from coal fly ash with simultaneous on-site utilization of CO2.

Mesoporous Al2O3 with crystalline framework walls has expanded all over the world due to the various potential applications especially in catalysis. Here, we develop a green and facile approach for the conversion of coal fly ash (CFA) into ordered mesoporous γ-Al2O3. The practical and promising lime-sinter method was comprehensively studied for the extraction of aluminum from CFA as a first step. The extraction efficiency of aluminum could reach up to 87.42%, through calcining with CaCO3 at 1390°C for 1 h and then dissolving in Na2CO3 solution at 70°C for 0.5 h. Combined with the urgent demand for CO2 emission reduction, simulated purified flue gas was introduced to precipitate the Al(OH)3 precursors without structure-directing agents for just 1 h, followed by calcining at only 400°C or 550°C. A series of characterizations were conducted to discuss the effect of precipitation temperature and calcination temperature, resulting the superior product (Al2O3-65/550) with high surface area (230.3 m2 g-1), crystalline γ-Al2O3 phase and ordered mesostructure. This proposed strategy, integrating the on-site recycling of CFA and utilization of CO2, appears to be promising for scalable production of mesoporous γ-Al2O3.