| Along with the rapid development of science and technology, the study of zeolites is expanding and innovating in material chemistry field. Zeolites are widely used in petrochemical industry and air separation industry because of their superior performance in adsorption and catalysis, and the self-properties of zeolites affect the production efficiency directly. Reducing the cost of production and decreasing energy consumption in industrial production are positive response to the national policy, so that, developing superior performance adsorbent is the key to the development of air separation technology.In general, synthetic zeolites are tiny particles, which can be used in industry after adding a certain amount of binder. Kaolin is a frequently-used binder, which have the abundant reserves in our country that can be used in industry abundantly.This paper has chosen kaolin as a binder to mix with power LSX, and transformed kaolin to metakaolin by calcination, then immersed in alkaline liquor by hydrothermal crystallization to prepare the binderless low silicon X-type zeolite. We have investigated the influence of crystallization conditions. After choosing the best crystallization conditions, we have used K+, NH4+, Li+to exchange zeolite and have investigated the influence of ion exchange on crystal structure and adsorption performance of zeolite. The results of the research included the following two parts:(1) The research results of the crystallization conditionsWe have investigated the change of crystal forms and relative crystallinity on zeolite when concentrations of NaOH solution are 1,1.2,2,3,4, 5mol/L separately.When concentrations of NaOH solution were 1,1.2,2mol/L, crystallization times were 5h,8h, temperature was 90℃separately, the optimum condition was: the concentration of NaOH solution was 2mol/L, crystallization time was 5h and temperature was 90℃. When the concentrations of NaOH solution increased, there was SOD crystal appeared. When the concentrations of NaOH solution was 2mol/L, crystallization time was 5h, the relative crystallinity of zeolite was better in temperature 95℃than 90℃.In conclusion, we chose the concentration of NaOH solution was 2mol/L, crystallization time was 5h, temperature was 95℃as the best crystallization condition.(2) The influence of K+, NH4+, Li+exchanges on crystal structure and adsorption performance of zeoliteFrom the results we have discovered the intensity of some characteristic peaks on zeolite decreased with the increase of K+exchange degree. K+ exchange made some peaks on zeolite LSX move towards to small angle, and it indicated K+exchange changed the crystal structure of zeolite.The CO2/N2 ratio of zeolite by K+exchang increased and achieved more than 20 on average, so that this zeolite was appropriate for remove N2 from CO2 gas separation and purification.NH4+exchange made peaks on zeolite LSX decrease, and the higher the exchange, the lower the peaks.Li-LSX kept crystal structure of LSX zeolite better which was prepared by LiOH solution exchanging NH4+-LSX, and peaks on Li-LSX moved towards to big angle. Li-LSX which was prepared by this method had higher N2 adsorption than power LSX, and it was 2.5 times N2 adsorption of power LSX. O2 adsorption increased too, but was inferior to the increase of N2 adsorption, so that the ratio of N2/O2 increased, which was more suitable to be used in the separation of nitrogen and oxygen.Comparing Li-LSX prepared by this method with Li-LSX prepared by LiCl exchang more than once, N2 adsorption of the former was half of the latter, but the lithium consumption of the former was 15 parts per million of the latter. So that Li-LSX which was prepared by LiOH solution exchanging NH4+-LSX was more suitable to be used in Pressure Swing Adsorption (PSA) technology.
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