Synthesis and CO2 adsorption performance of high Si/Al ratio DDR zeolites prepared from silica fume

DDR zeolite for CO2 separation can be prepared cheaply using silica fume as raw materials, compared with current preparation method using chemical reagents as raw materials. In this paper, it is investigated the effects of alkalinity, crystallization time, dosage of organic template agent 1-amantadine (ADA), crystallization temperature, and H2O/SiO2 (molar ratio) for preparing DDR zeolite by hydrothermal synthesis from industrial waste silica fume. The trend of Al in silica fume entering the DDR zeolite framework under different alkalinity was studied. Considering the time cost, energy consumption, and product quality, the optimum synthesis condition was determined to be 1 SiO2: 0.3 ADA: 0.6 NaOH: 100 H2O at 160 °C for 24 h and the DDR purity could reach to 86.85%. With the increase of alkalinity in the system, the Si/Al ratio of DDR zeolite framework decreased and the crystal morphology changed from the larger biconical type to the smaller hexagonal sheet type, which led to the adsorption performance of CO2 increased. This study not only reduced the synthesis cost of DDR zeolite but also used industrial solid waste with high-added value to realize the transformation of waste into treasure.