Template-free Synthesis And Performance Study Of SSZ-13 Molecular Sieve

Carbon dioxide is the main cause of greenhouse effect.Continuous increasing of global carbon dioxide emissions attaches great significance to the capture and storage of carbon dioxide.SSZ-13,a highly stable microporous zeolite?pore size 0.38×0.38 nm?with CHA topological structure,shows high specific surface area and regular pore structure,which leads to excellent adsorption capacity for carbon dioxide.The traditional synthesis method of SSZ-13 zeolite employs highly cost N,N,N-trimethyladamantine ammonium cation?TMADa⁺?as structure-directing agent.Moreover,the difficulty in controlling the ratio of ingredients together with the long hydrothermal synthesis time further increase the cost of SSZ-13.Therefore,in this paper,SSZ-13 zeolite was synthesized by using glass fiber as silicon source without adding organic template,and carbon dioxide adsorption was studied on the synthesized zeolite.The main contents are list as follows:?1?On the basis of absence of organic structure directing agent,SSZ-13 zeolite was prepared by traditional hydrothermal synthesis method in fluorine-containing system with glass fiber as solid silicon source.In the hydrothermal reaction process,the reaction of silicon and aluminum species with Na OH is transmitted through the liquid phase,and the crystal growth characteristics of SSZ-13 zeolite are consistent with those of liquid supersaturated system.By characterization of powder X-ray diffraction?XRD?,cold field scanning electron microscope?SEM?and Fourier infrared spectroscopy?FT-IR?,the optimum conditions for synthesis of SSZ-13 zeolite are obtained:molar ratio of 3.0 Na₂O/1.0 Al₂O₃/3.5 Si O₂/250 H₂O/1.0 NH₄F,hydrothermal crystallization temperature of 120?,hydrothermal time of 24 hours.SEM shows that the product is spherical particles?particle size of?10?m?assembled by nano size particles.?2?In order to reduce the environmental pollution caused by fluorine ions,SSZ-13 zeolite was synthesized by hydrothermal method without using organic structure directing agent and fluorine ions.By XRD,SEM and FT-IR analysis of SSZ-13 zeolite,the optimal conditions for hydrothermal synthesis of SSZ-13 zeolite are obtained:molar ratio of 2.5 Na₂O/1.0 Al₂O₃/3.5 Si O₂/250 H₂O,crystallization temperature of 120?,hydrothermal reaction time of 24 h.Compared with the synthesis of SSZ-13 zeolite by adding fluorine ions,the basicity of the synthesis system is lower.The synthesized SSZ-13 zeolite is a spherical particle formed by the accumulation of nanoparticles with the particle size of 5?15?m.The ratio of silicon to aluminum?Si O₂/Al₂O₃?is 2.9 and all species are well crystallized without formation of extra-framework Al,according to ICP,²⁹Si and²⁷Al NMR.Due to the low Si/Al ratio of zeolite,the pore channel of Na-SSZ-13 shows a certain alkaline environment,which is conducive to the adsorption of acid gas carbon dioxide.The zeolite shows good adsorption ability for carbon dioxide by investigation of the adsorption isotherms of carbon dioxide at 263?308 K.At 298 K,the maximum amount of CO₂adsorption is 1.92 mmol/g.