Hu Tao, Gao Wenyan, Liu Xin, Zhang Yifu, Meng Changgong
School of Chemistry, Dalian University of Technology, Dalian 116024, People's Republic of China.
R Soc Open Sci. 2017 Oct 18;4(10):170921. doi: 10.1098/rsos.170921. eCollection 2017 Oct.
Zeolites Na-A and Na-X are important synthetic zeolites widely used for separation and adsorption in industry. It is of great significance to develop energy-efficient routines that can synthesize zeolites Na-A and Na-X from low-cost raw materials. Coal fly ash (CFA) is the major residue from the combustion of coal and biomass containing more than 85% SiO and AlO, which can readily replace the conventionally used sodium silicate and aluminate for zeolite synthesis. We used NaCO to replace the expensive NaOH used for the calcination of CFA and showed that tablet compression can enhance the contact with NaCO for the activation of CFA through calcination for the synthesis of zeolites Na-A and Na-X under mild conditions. We optimized the control variables for zeolite synthesis and showed that phase-pure zeolite Na-A can be synthesized with CFA at reactant molar ratio, hydrothermal reaction temperature and reaction time of 1.3NaO: 0.6AlO: 1SiO: 38HO at 80°C for 6 h, respectively, while phase-pure zeolite Na-X can be synthesized at 2.2NaO: 0.2AlO: 1SiO: 88HO at 100°C for 8 h, respectively. The composition, morphology, specific surface area, vibration spectrum and thermogravimetry of synthesized Na-A and Na-X were further characterized.
钠-A型和钠-X型沸石是重要的合成沸石，在工业上广泛用于分离和吸附。开发能够从低成本原料合成钠-A型和钠-X型沸石的节能工艺具有重要意义。粉煤灰（CFA）是煤和生物质燃烧产生的主要残渣，含有超过85%的SiO₂和Al₂O₃，可轻松替代传统用于沸石合成的硅酸钠和铝酸钠。我们使用Na₂CO₃替代用于粉煤灰煅烧的昂贵NaOH，并表明压片可以增强与Na₂CO₃的接触，通过煅烧活化粉煤灰，以便在温和条件下合成钠-A型和钠-X型沸石。我们优化了沸石合成的控制变量，并表明在反应物摩尔比、水热反应温度和反应时间分别为1.3Na₂O: 0.6Al₂O₃: 1SiO₂: 38H₂O、80°C和6小时的条件下，可以用粉煤灰合成纯相钠-A型沸石，而在2.2Na₂O: 0.2Al₂O₃: 1SiO₂: 88H₂O、100°C和8小时的条件下，可以合成纯相钠-X型沸石。进一步表征了合成的钠-A型和钠-X型沸石的组成、形态、比表面积、振动光谱和热重分析。
