用于分离CH4和CO2的Al2O3/SAPO-34核壳材料的制备研究

Based on the adsorption mechanism of methane and carbon dioxide on different adsorbents, we will prepare γ-Al2O3/SAPO-34 core shell composite as sorbent to separate methane and carbon dioxide. The core is γ-Al2O3 with porous structure, good abrasion performance and low cost, and the shell is microporous zeolite SAPO-34 with 0.38nm pore size which is between the critical diameter of CO2(0.33nm) and CH4(0.38nm). The core shell composite is prepared by in situ crystallization and secondary growth process. The separation performance of core shell composite is tested in dynamic adsorption experiments using methane and carbon dioxide as adsorbate. The effects of synthesis parameters on the microstructure and morphology are investigated. The relationships between surface properties, microstructure and the separation performance of CH4 and CO2 are revealed. The mechanism of separation CH4/CO2 and the mass diffusion of molecular in the core shell composite are illuminated. The item is in the need of lower energy consumption and discrease pollutants discharge. It also has scientific significance and applied value to promote the application of landfill gas and pressure swing adsorption.

本项目根据二氧化碳和甲烷在不同吸附剂上的吸附机理，以具有多孔结构、耐磨性好、成本低的γ-Al2O3为核，孔径(0.38nm)介于CO2(0.33nm)和CH4(0.38nm)的临界分子直径的微孔分子筛SAPO-34为壳，采用原位晶化及二次合成的方法制备核壳材料γ-Al2O3/SAPO-34，并采用动态吸附分离的方法考查其对CH4与CO2的分离性能。研究合成条件对核壳材料的微观结构及形貌控制的规律。阐明核壳材料的表面性质及微观结构与CO2/CH4分离性能之间的内在联系。揭示核壳材料分离CH4和CO2及气体分子在核壳材料中传质扩散的机理。项目符合我国当前节能降耗的要求，对于推进垃圾填埋气的应用与拓宽变压吸附分离应用领域具有重要的科学意义和应用价值。

城市垃圾卫生填埋场产生的气体——垃圾填埋气（Landfill Gas，LFG）中主要气体甲烷和二氧化碳的分离引起人们的广泛关注。本项目通过原位晶化及二次合成的方法制备γ-Al2O3/SAPO-34核壳材料，并对其吸附分离性能进行表征，并在此基础上进行A型分子筛进行了制备，为核壳材料的延伸奠定了基础。通过对γ-Al2O3进行镧改性，在不改变其比表面积及孔结构的情况下提高其热稳定性。考察了原位晶化和二次合成制备γ-Al2O3/SAPO-34核壳材料，结果发现原位晶化不适合在γ-Al2O3表面进行SAPO-34分子筛的制备。考察了晶化时间、陈化时间、反应体系中水含量、磷酸含量以及添加表面活性剂CTAB对SAPO-34晶种影响，对比了滴涂法和滴涂-wriping法对晶种铺设情况的影响，并进一步考察了合成温度及合成时间对γ-Al2O3/SAPO-34核壳材料形貌的影响；对三种吸附剂进行了吸附分离研究，得到了甲烷和二氧化碳在吸附剂上的吸附容量和分离因子，说明了γ-Al2O3/SAPO-34核壳材料的性质与CO2/CH4分离性能之间的内在联系。通过本项目的实施，对于处理垃圾填埋气的二次污染问题有一定的借鉴意义。